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lesson 1 introduction autocad is a computer aided design (cad) program used by just about every engineering and design office in the world. although there are alternative cad packages, autocad is by far the most widely used system. autodesk's autocad is the industry leader in cad packages. used by civil engineers, architects, mechanical and electrical engineers, aeronautical engineers plus many other disciplines. there have been several versions of autocad over the years, with each new version introducing new and more powerful features than its predecessor. the latest version of autocad (at the time of writing) is autocad 2005. accurate, scale drawings can be created and published using autocad’s powerful features. 3d 'models' can also be created giving the designer absolute control over the design from start to finish. the computerized model can be viewed through a 360º angle, and even 'rendered' with a texture on screen to give an idea of the finished product. a 3d model of a component created by autocad with a rendered view of the model to the top right). as with most new skills, you have to learn to walk before you can run! the drawing shown above will have been created by an experienced autocad user with many years experience behind him. the purpose of the basic tutorials contained within this site is to give you a sound understanding of the basics of autocad. enough of the background, lets get on to the interesting stuff!
lesson 2 opening autocad open up autocad, you should be greeted with a screen asking if you want to open an existing drawing or start from scratch. (dependant on your version of autocad, the screen will be slightly different - the image shown below is for autocad 2002).
select 'create drawings', then 'start from scratch'. ensure that you select metric (i.e. you are telling autocad that you will be drawing in meters and millimeters not feet and inches). autocad will now create a new drawing file named drawing1.dwg. autocad will default to 'model space'. for now it is sufficient to say that model space is the blank space where all the drawing is carried out. paper space (now called layout space since autocad 2000) isn't really required until we are ready to plot (print) the drawing. toolbars there are many toolbars available in autocad. go to view > toolbars from the drop down menu to see them all. for now make sure that the following toolbars are checked: draw - contains autocad’s most common drawing tools modify - contains all of the common editing commands such as erase, copy etc. object properties - contains 'layer' information as well as object colors and line style options. (covered later). standard toolbar - contains open & save options as well as zoom & pan options. object snap - autocad's intelligent drawing aid - joins lines at specific points. (covered later). arrange the icons to where is comfortable for you (a typical layout is shown below):
the command line the command line appears at the bottom of the autocad screen (as shown above) and displays the commands entered. commands can be entered into the command line in text format, or by using the icons or drop down menus. 'old school' cad users tend to type each command into the command line, as was required with older
versions of autocad. it is much quicker to familiarize yourself with the tool bars and drop down menus. there are times however when commands need to be typed into the command line, these will be covered later. drawing technique - autocad's co-ordinate system just before we start drawing, one more important point. autocad works on a coordinate system. when drawing, we can be very precise and specify an exact point in space where a line should begin or end. the 2d co-ordinates system is based on the horizontal and vertical axis named x and y. (this is shown in the bottom left of the autocad drawing area, the x y icon is called the ucs). drawing - line command 1) select the line command from the draw menu the 'draw' drop down menu).
(alternatively select line from
2) autocad asks you (in the command line area) to specify a start point. simply pick an area central to the drawing area (left click of the mouse). 3) autocad now asks for an end point. select somewhere (left click) to the top right of the drawing area. 4) now one line is drawn. autocad keeps the line command open so that another line can be drawn beginning exactly where the previous finished. we want to end the command so simply right click to end (autocad 2000 users and above - right click will open a small menu - simply choose 'enter' to end the command). drawing - line command - specifying points erase the line we just created. select the erase command from the menu or from the 'modify' drop down menu. autocad asks you to select an object, left click the line we drew. right click to enter the command and delete the line. let's imagine we are looking down over a plot of land (plan view). we are going to draw the land boundary from some measurements taken. the land measures 25m x 40m. 1) select the line command as before. this time for a start point we will specify some co-ordinates (simply an exact point in the drawing area.) 2) we will start our drawing at a point 50m horizontal and 50m vertical from the default ucs location of 0,0. autocad is asking for a start point, type in the command line: 50,50 followed by hitting enter. note - autocad's normal co-ordinate system is always relative to the ucs icon position of 0, 0.
3) for the next point we'll draw the bottom end of the plot of land. we want a line 25m horizontal from the start point. we can specify co-ordinates from a particular
point by including the @ symbol in front of the co-ordinates. this informs autocad that the co-ordinates we are specifying are relative to the last point specified and not to the ucs. to enter a 25m length horizontal line from the start point the command would be @25,0 (i.e. go 25m along, go 0m up).
now we should have drawn a horizontal line 25m long. note - do not right click to end the line command, this layout can be drawn leaving the command open. 4) we now need a 40m vertical line to represent the right side of the plot of land. this command would be @ 0, 40 (i.e. go 0m along, go 40m up). 5) now for the top of the land. we need to go back horizontally by 25m from the current end position of the vertical 40m line. the command would be @-25, 0 (i.e. go back 25m, go up 0m). 6) to finish off we need to draw the last line. we need to go 40m vertically down so the command is @0,-40 (i.e. go 0m along, go 40m down). 7) right click to end the draw command. that's it! we've just drawn a scale drawing of the plot of land from the measurements given from a start point of 50, 50 relevant to the ucs. tip- if your drawing is only taking up a small area of the screen, try zooming in with the various zoom commands. to quickly view your drawing close up choose zoom extents
to see the entire drawing.
drawing - rectangle command erase the 4 lines we just drew. we will know try a command that would have drawn the above land layout in one simple command. 1) choose the rectangle command
or select it from the draw drop down menu.
2) autocad asks for the start point. as before, we want to begin 50m horizontally and 50m vertically from the ucs, so enter 50, 50 then hit return. 3) autocad now asks for the position of the top right corner of the rectangle we are going to draw. to draw the plot of land we need 25m along and 40m up from the start point, so the command is @25, 40 your drawing should be identical to the one we drew before, but was a lot simpler and quicker to draw. have a play around with the line and rectangle commands and familiarize yourself with how they operate.
lesson 3 zoom commands here we'll take a quick look at the various zoom commands available, and their uses. this tutorial requires you to download the autocad drawing file lesson3.dwg lesson3.dwg (autocad 2000 file version) lesson3r14.dwg (autocad r14 file version) 1) load up the file, the drawing is of a steel plate with 6 mounting screws. to see all of the available zoom commands, the zoom toolbar needs to be visible. load in the zoom toolbar (for those who can't remember: go to the 'view' drop down menu, then select toolbars. check the 'zoom' box then choose close. move the toolbar to a convenient location) autocad's zoom command toolbar:
commands (from left to right): zoom window : select a window over the location to zoom into. autocad will zoom in close to the object including everything within the selection box. zoom dynamic: enables the user to set the size of a standard zoom window type box, then use this box to select zoom in views of the drawing with this box with clicks of the mouse button. (not as powerful as zoom window in my opinion) zoom scale: enables the user to zoom into the drawing to a known scale (referred
to as an 'xp value'). this type of zoom is not required until you are ready to plot the drawing. don't worry, you're not expected to understand the use of this command yet! it will be covered in the paperspace/layout view tutorial. zoom centre: specify a centre point, then a radius and autocad will centre this view to fit your screen. zoom in: pretty simple, zooms into the drawing slightly by each click! quick 'n' simple! zoom out: same as above, but zoom out by each click. zoom all: zooms to the extents of the drawing limits. don't worry about this just yet. zoom extent: this is a very useful command. one press will zoom to the extent of the entire drawing enabling a very quick overview of the project and an easy starting point to zoom into a more precise area of the drawing with one of the above tools. 2) you should have the lesson3.dwg file open in autocad. if not then open it up now. time to try some zoom commands out. 3) press the zoom window button. autocad asks for the first corner of the box you are about to draw. this corner can be any corner of the zoom box we will specify. choose an area just to the top left of the left side middle screw (see below). autocad now asks for the opposite corner, select to the bottom right of the screw ensuring the screw is clearly inside the zoom box. you should now have a clear view of the screw.
4) now try the zoom in and zoom out buttons. notice how they knock the zoom in and out by a set amount each time, just comfortable enough to get a wider/closer view where required.
5) now press the zoom extents button. this zooms back to see the entire drawing centered in the screen. have a play with the commands, viewing different areas of the drawing until you feel comfortable manipulating the zoom to suit the view you require. zoom real-time / pan command by now you should be comfortable with operating the zoom commands. now we'll try the easiest and perhaps most used zoom command available, zoom real-time. this command is located on the toolbar named 'standard toolbar'. 1) select the zoom realtime button
2) this command will zoom in and out of the drawing dependant on how far you move your mouse. left click and hold the left mouse button down. autocad will zoom in further into the drawing the further you move you mouse up (away from you). try pulling the mouse down with the left button still held down, autocad will zoom out. once mastered, zoom real-time will become your preferred method of quickly zooming into a drawing. 3) now we'll introduce a command which quickly enables you to change the view of the screen without altering the zoom. you probably noticed that while zooming with any of the above commands, you sometimes wanted to view either further left, right, up or down on the drawing. this wasn't possible with the zoom commands without zooming out and then zooming in again showing the area you require. the pan tool enables us to control exactly which area we are viewing. 4) select the pan button 5) while holding the left mouse button, pull the mouse to the left, right, up or down. notice how the pan tool reflects these mouse movements on screen so we can move around the screen effortlessly. top tip! - combining the zoom real time and pan commands is by far the quickest way to navigate a drawing. while either command is open, try right clicking the mouse in the drawing area to bring up a small menu where the most common and useful zoom commands can be quickly selected: pan, zoom (real-time), zoom window and zoom extents. get used to right clicking to change zoom commands to easily navigate any autocad drawing. just one last note, but an often misunderstood concept for new autocad users. zooming does not affect the drawing scale in any way. the dimensions of the drawing remain the same! we are simply manipulating the view. for example; a car viewed from a plane traveling at 10,000ft appears quite small, when viewed from 25,000ft it appears tiny! the size of the car however has not altered; we are simply viewing it from further away! that concludes our zoom and pan tutorial!
lesson 4 drawing limits
in the previous tutorial, drawing limits were mentioned while explaining the use of the zoom all command. when the zoom all command is chosen, autocad zooms to the extent of the user defined limits. limits can be thought of as the extent of the drawing area. the autocad drawing area is, in theory, infinite. as long as you continue to draw, autocad will continue to give you the drawing space. if thought of in practical terms, if we were to manually pencil draw a 1:1 scale (full size) drawing of a wrist watch, why draw it on an a0 sized sheet of paper when a4 size is adequate? autocad drawing limits follow the same logic. we can tell autocad the drawing space we require (although we have the option to increase this if we so desire at a later stage). autocad will display a grid to the extent of the drawing limits specified. let’s have a go: 1) start a new autocad drawing. 2) start the line command 3) for the start point, enter 0.2,0.2 for the next point enter @0,0.52 4) for the next point enter @0.37,0 5) for the next point enter @0,-0.52 6) to close the box, we'll try a new technique. normally, we would now enter @0.37,0 to draw a horizontal line back to the start position to close the box. as we have drawn all 3 lines keeping the line command open, there is a quicker way to draw the box. type the letter c in the command line (the c stands for close) to draw a line from the current location back to the start point. your screen should be similar to the screen shown below (you may have to zoom extents to see the entire drawing).
7) now try using the zoom all command. the drawing will be barely visible (if at all). this is because the default limits are not set correctly for our drawing. we need to enter new drawing limits. 8) type limits directly into autocad's command line. you will be asked to specify the lower left co-ordinates (remember - in relation to the ucs). hit enter to accept the default value of 0.0000, 0.0000. 9) autocad now wants us to specify the upper right limit co-ordinates. there is no right or wrong value, but it should be set to a sensible value for the drawing size. our drawing is only 0.52m x 0.37m. let’s enter an upper limit of say, 1m, 1m from the ucs. enter 1, 1 into the command line and hit enter. 10) now try the zoom all command again. the view should be much closer as it is set to the drawing limits. some professional autocad users manage to go their whole careers without ever altering autocad's limit setting, and quite frankly: - it's easily done! there will be many times (especially if like me, you never use the zoom all command and grid!) that adjusting autocad's default limit settings has no advantage. why mention it then? well... occasionally while panning your pan icon may gain a line next to it (dependant on the pan direction) and you can't pan any further. this is because the limits have been reached and autocad refuses to let you see beyond your defined drawing areas. you may then require entering the limits command and changing the default setting. try panning away from the drawing we just made, as soon as you hit the 1m drawing limit we set, we can't pan any further. just in case you were curious, the drawing is of a dvd case (520mmx370mm). if we were to have drawn the case in millimeters instead of meters (i.e. we decide one autocad unit shall equal 1mm instead of 1m - perfectly acceptable to do) then a much larger upper right drawing limit would have been required, perhaps 1000, 1000.
that's about all there is to know about drawing limits!
polylines polylines draw lines similar to the line command we used in lesson 2, but are a lot more powerful. let's start by drawing the same plot of land we drew in lesson 2, but this type using polylines. the polyline command is situated on the 'draw' toolbar. 1) choose the polyline command 2) for a start point, enter 50, 50 3) now enter the next line end points: @25,0 @0,40 @-25,0 c right click or hit enter to end the polyline command. 4) try selecting any part of the area we just drew with one click of the left mouse. the lines will become dotted to show that you have selected the polyline. you will notice that although we entered each line end point command separately, because we drew the area with the polyline command left open, autocad treats the polyline as one entity regardless of the shape or direction of the lines.
see the blue squares at each corner of the drawing?, these represent each line point specified when we drew the polyine. they are also a handy quick editing tool to adjust the shape of our drawing. try left clicking on one of the blue squares with the centre of your crosshair; the corner follows your mouse movements. left click to reposition the corner where your crosshair is, or press the escape key to let go. these blue squares are called grips. try using the grips to dramatically alter the shape of your land layout.
(tip- to undo any changes you make, simply select undo from the edit drop down menu as often as required) advanced polylines - arcs there is more to polylines than just grips, a polyline can actually be any shape or thickness. now we'll have a play with some more interesting polyline features. 1) undo any changes you made to the rectangular land layout we drew, and zoom extents to be left with the layout as shown above. 2) select the polyline command. notice the command line is asking for a start point; choose somewhere central within the upper area of our plot of land. 3) autocad now asks for a next point or we can choose further drawing options:
the options are: arc, halfwidth, length,undo,width. to select which option we require, enter the letter from the command we require that is in upper case (which is most often, but not always, the first letter of the word). 4) we are going to draw a pond on the land, so enter a for arc. 5) notice how the line becomes arced instantly? select a few points and close the polyline to get something similar to the drawing shown below.
note: when you enter 'c' for close, autocad will ask you to clarify you want to use the close command and not centre (as they both begin with c). enter cl for close which is the two upper case characters). the arc command is obviously not just for drawing free-hand ponds! we can enter further commands within the arc command by using their upper case letters to have more control over the arc, such as specifying a radius. have a play with the arc command and get familiar with how it functions. advanced polylines - width 1) now we'll draw a fence around the pond. select the polyline command again; select a point close to the edge of the pond to begin the polyline. 2) press w to activate the polyline width command. by default the polyline width command is set to 0. autocad asks for a width for the start of the line, enter 0.1
then hit enter. autocad now asks for the width for the end of the line, as we want it to be the same thickness, enter 0.1 again. now just try drawing a free hand fence around the pond. the thickness command is very useful, the more that you use autocad the more reasons you'll find to use it! try drawing a new polyline with a starting width of 0, and an ending width of 1. a handy arrowhead pointer? that’s about it for polylines! they may not seem so great just yet, but when we start using modify commands you'll see just how useful it is to be able to manipulate and select a whole complex shape in one go rather than selecting all the separate entities.
basic modify commands here we'll cover the modify tools, which give us control over simple shapes we have created. as the name suggests - we can modify drawing elements. this is what the modify toolbar looks like (if you don't see it, check the modify box in 'view toolbars'):
the modify tools (from left to right): erase, copy, mirror, offset, array, move, rotate, scale, stretch, lengthen, trim, extend, break at point, break, chamfer, fillet, explode. erase - select this button then a drawing element to erase it permanently from the drawing. copy - the copy command will copy any selected drawing elements and reposition where specified by the user, without affecting the original elements. 1) select the copy button, then select the object(s) to copy then hit return (or right click) 2) select the base point where to copy from (for example if copying a circle, it would be sensible for the base point to be the centre of the circle) 3)enter the second point of displacement - this is where the new base point of the copied objects is to be positioned. note that the base point is not visible, just a co-ordinate in autocad’s drawing system to enable accurate positioning of objects where required. when quickly copying an object it is quite acceptable to simply pick a rough point to copy and then position an object without specifying co-ordinates, it can then be accurately positioned in the drawing area using the move command. mirror - the mirror command will create a mirror image of any selected drawing elements along any line of symmetry specified by the user. mirror tutorial files: lesson6 - mirror.dwg (autocad 2000/2002 file version) lesson6 - mirror r14.dwg (autocad r14 file version) 1) open the drawing file. it should look like the one shown below:
2) select the mirror command from the modify toolbar (or choose 'modify - mirror' from the drop down menus) 3) select the blue object (looks like half a wine glass?!) 4) we are now prompted to specify the first point of the mirror line, choose the centre of the cross marked 'a' 5) we now need to enter the second point of the mirror line, select the centre of the cross marked 'b' handy tip!: to draw a true vertical or horizontal line, hit f8 or click 'ortho' at the bottom of the command line to enable autocad’s ortho function, which limits the available pointer selection points to horizontal or vertical positions relative to the first point selected. ortho can be used with all commands. 6) autocad now asks if we want to delete the source object. we need to enter 'y' for yes or 'n' for no (simply hitting enter would accept the default setting of 'no'). deleting the source object results in a mirrored copy of the original object, without the original object. in this case we want to keep the original object to complete the drawing. enter n for no followed by enter. you should now have a simple drawing of a wine glass as below.
offset - offset will make a copy of a line or series of selected lines by a specified distance in the direction specified. the example below shows an original red box (50mm x 50mm) with an offset yellow box 10mm to the outside of the original box.
the offset command simply creates a copy of the selected objects, at the distance specified, to either side of the original object. 1) create a new drawing and draw a rectangle ordinates 10,10 at a size 50,50.
2) 3) 4) 5)
from a base point of co-
select the offset command when prompted for an offset distance, enter 10. when asked to select an object, select the rectangle we drew. autocad then asks for a side to offset. if we select a point outside of the
rectangle then a new rectangle will be created outside of the original at a 10mm offset. selecting a point within the rectangle would create a rectangle within the existing rectangle at a 10mm offset. select a point outside of the rectangle. you should have an image similar to the one shown above. offset can be used on any shaped objects, polylines, lines rectangles, circles etc and can be a very useful command. the top arc piece of the wine glass tutorial above was originally drawn using the offset command to give a thickness to the glass. array - the array command quickly creates copies of a selected object(s) to a specified spacing. the array command can save lots of drawing time when used correctly. there are two types of array; rectangular and polar. a rectangular array would create copies of an object in rows and columns at specified spacings. a polar array would create copies of an object in a circular pattern based on a specified centre point. shown below are the two types of array. the red objects are the original objects, and the yellow are the copies created with the array.
rectangular array download the appropriate tutorial file for your version of autocad: lesson6 - array.dwg (autocad 2000/2002 file version) lesson6 - array r14.dwg (autocad r14 file version) (autocad r14 array options are not in a dialogue box although the same settings apply) the drawing is a plan view of a chair. we will use the array command to create more chairs at a regular spacing of 1000mm centers as shown in the above example. 1) open the autocad file, select the array button
2) select 'rectangular array' 3) for select object, select the chair 4) for the rows and columns, we will select 5 each time. this tells autocad to repeat the object 5 times horizontally and 5 times vertically. 5) for column offset and row offset enter 1000 6) autocad 2000, 2002 users select the ok button.
an array will have been created with the rows, columns and spacings specified. your drawing should be similar to the rectangular array drawing shown above. polar array download the appropriate tutorial file for your version of autocad: lesson6 - polar array.dwg (autocad 2000/2002 file version) lesson6 - polar array r14.dwg (autocad r14 file version) (autocad r14 array options are not in a dialogue box although the same settings apply)
1) open the autocad file, select the array button 2) select 'polar array' 3) for select object, select the entire drawing (the circle and vertical line) 4) for centre point, choose the bottom end of the vertical line. this is the point where the copies of the original object will be rotated about. 5) for number of items, enter 12. 6) for angle to fill, enter 360. (we have just told autocad to array 12 items about the centre point for a full 360°)
your drawing should look similar to the one shown below:
move - the move command works exactly the same as the copy command described above, except instead of creating a copy of the selected objects, the second objects are moved. rotate - the rotate command rotates any selected objects about a defined point by the angle specified. by default autocad will rotate objects anticlockwise when an angle is entered. 1) load the drawing lesson6 - polar array.dwg that we used in the polar array example. 2) select the rotate button from the modify toolbar. 3) select the vertical line and circle. 4) select the base point for the rotation. this is the point which the selected objects will be rotated about. select the bottom end of the vertical line. 5) autocad asks for a rotation angle. note how mouse movements rotate the object in real time enabling quick rotations to be made. we will specify an angle of 45°. enter 45 and hit enter.
the object should have been rotated as shown above. scale - the scale command scales the size of a selected object(s) by a defined scale factor from a selected base point. the selected objects can be scaled up to increase size or down to reduce the size. for example: entering a scale factor of 2 would result in the object being doubled in size. entering a scale factor of 0.5 would result in the selected object being halved in size. try scaling the object we rotated in the above rotate tutorial, to get a feel for how the scale command operates. stretch - the stretch command will stretch a selected part of an object, and can be used to lengthen or shorten a particular object. looking at the stretch command introduces two very different ways of selecting objects. so far you have probably been 'picking' an element of a drawing with one single click of the mouse while the cursor is over the object. a quicker way is to pull a window over the objects we want to select. there are two ways to select objects with a window, with each method yielding different results. a window drawing a box from top left to bottom right will select all objects fully within the window. drawing a window with a box from bottom right corner to top left will result in all objects being selected that any part of the window passes through.
the selection window (shown green) with a box drawn top left to bottom right results in the objects within the window being selected as shown on the second image shown above. note that the circle only partially within the window does not get selected.
the selection window shown green above (note how the different window selection type is shown as dotted) results in all objects within and passing through the selection window become selected. now we know the different selection types we can have a go with the stretch command. 1) download and open the original polar array lesson drawing above. 2) select the stretch command button 3) use the bottom right to top left window type to draw a dotted window around the end of the object as shown below:
4) autocad asks for a base point, select around where the line and circle meet. 5) notice how where we move the mouse the object is becoming stretched. we can simply select a point with the mouse to stretch the object, or enter a more accurate position such as @0, 50. lengthen - the lengthen command will lengthen a selected line. when the lengthen command is activated, before the line is selected, we need to tell autocad how we will lengthen the line.
de - delta: autocad asks for a distance to lengthen the line by, when the line is selected it will then be lengthened by the specified distance only to the side of the line where the line was selected. i.e. if when you selected the line, you selected it just to the left of centre, then the left side of the line would be lengthened. p - percent: autocad asks for a percent to lengthen by, and then asks you to select the line. specifying 50% would reduce the size of the line by half (the same effect as scaling by a factor of 0.5). specifying 100% would result in no change in length. 200% would double the length of the line. when specifying the percentage to autocad only the numerical figure has to be entered and not the percent (%) symbol. t - total: autocad asks for the distance you want the entire line to be, when you select the line it will adjust the lines length to the distance specified. dy - dynamic: autocad adjusts the length of the line as the mouse is moved in the direction the line is to be lengthened. this is not an accurate technique, although is useful for quickly lengthening construction lines for example. trim - the trim command is an extremely useful tool which will erase all parts of an object beyond or within its intersection with another object.
the protruding yellow lines on the image on the left have been trimmed to the edge of the rectangle as shown on the right image the trim command is easy to execute provided that this one very important rule is obeyed: when first prompted for an object, you must choose the object you wish to use as the 'cutting edge' and not the object to be trimmed. i.e. the cutting edge in the above example was the rectangle, the vertical and horizontal lines were trimmed to this edge. trim tutorial files: lesson6 - trim.dwg (autocad 2000/2002 file version) lesson6 - trim r14.dwg (autocad r14 file version) we are going to trim the yellow lines in the drawing to end at the inside of the rectangle as shown in the image above.
1) open the above tutorial file into autocad. choose the trim command 2) when asked to select object we need to select the object(s) which will be the cutting edge! in this case it is the rectangle so select it and hit enter. we now are asked to select the objects to trim. it is important to note that where we select the object to be trimmed in relation to the object selected as the 'cutting edge' determines which part of the trimmed object is deleted, and which remains. if we were to select part of the yellow lines within the rectangle, then the selected objects would be deleted up to the inside edge of the rectangle (cutting edge). we want to remove the sections of the lines outside of the rectangle so: 3) select all 4 of the ends of the yellow lines outside of the rectangle. notice how they are removed as we select them. 4) hit enter to end the trim command. just remember, be aware what your cutting edge is! the trim command can be used on most objects within autocad. one common mistake beginners make is that they can't understand why autocad refuses to trim a circle to a single line which intersects the circle at one point only. if the circle were to be trimmed to one line, it would be deleted! any trim command on a circle must have two 'cutting edges' selected. extend - the extend command is similar to the trim command in how it functions, except it extends a selected line to a point of intersection of another selected object. in order to successfully use the command, you have to make sure that when the line is extended it will actually intersect the object selected which the line is to extend to! 1) download the trim tutorial file above and use the trim command we learnt to trim the yellow lines to the circle as shown below:
we will now use the extend command to extend the yellow lines back up to the edge of the rectangle 1) select the extend command
2) when asked to select an object select the boundary edge which the lines will be extended to. in this case we want to extend to the rectangle, so select the rectangle. 3) we are now asked to select the object to extend. as with the trim command, the effect of the command is dependant upon whereabouts along the length of the object it is selected. autocad will always extend the end of the line which is nearer to the point where the line was selected. select each end of the yellow lines (near the intersection with the circle) to extend each line up to the rectangular boundary edge we selected. 4) hit enter to end the command. break at point - the break at point command enables the user to break an object at a specific point, creating two separate objects. 1) draw a line that is roughly horizontal; don't worry about its size. 2) select the break at point command . when prompted to select object, select the line we just drew. 3) when prompted to select a break point, select somewhere along the length of the line. now try selecting the line, note how it is now broken into two separate lines, at the point we selected. this command can be used on most drawn objects within autocad. break - the break command is identical to the above break at point command, except the break line isn't as neat as when using the above command i.e. the break point leaves a significant gap between what is now two separate objects:
the top line was broken with 'break at point'. the bottom line was broken with the standard 'break' command. chamfer - the chamfer command will chamfer the intersection of two lines to a specified distance. this is best shown with the example below:
the rectangle on the left is 50mmx50mm. the rectangle on the right has been chamfered by a distance of 5mm. 1) draw a rectangle using the line command (not rectangle - we will see later) at a size of 50mm x 50mm. 2) select the chamfer button 3) we are going to chamfer the 50x50 rectangle by a distance of 5mm (as seen above). enter d for distance then hit return. 4) autocad asks for the first chamfer distance. enter 5 then enter. 5) autocad then asks for the second chamfer distance. in this case we are using the same chamfer distance, although autocad can draw a chamfer with two separate distances. as we want the same distance, input 5 then enter. we now need to select the two lines to chamfer. this would be the two intersecting lines we wish to chamfer. 6) select the first line to chamfer then enter. 7) select the second line then enter. the two line segments should be chamfered similar to the diagram shown above. repeat this procedure to chamfer the remaining 3 corners. you may have wondered why we drew the rectangle using the line command instead of the much quicker rectangle command. this is because the rectangle command draws the rectangle in the same manner as a polyline. we can't select the individual lines forming the rectangle, so we can't select the separate lines we wanted to chamfer. there is however a way to chamfer two polyine segments: 1) draw a rectangle with dimensions 50x50. 2) select the chamfer button , and this time enter p for polyline. 3) autocad asks for a 2d polyline, select the rectangle we drew. autocad automatically chamfers each intersecting line segment of the polyline to the last specified chamfer distance used (which should be 5mm as specified in the first part of the chamfer tutorial). to change the chamfer distance simply select the chamfer button, specify distance, enter the chamfer distance, when prompted to select an object simply hit return until out of the chamfer command. your new chamfer distance will now be set. handy tip: to join the ends of two separate lines, use the chamfer command with a distance of 0! fillet - the fillet command is very similar to the chamfer command above, except instead of creating a straight line chamfer, autocad creates a radius between the two points.
the rectangle on the left is 50mmx50mm. the rectangle on the right has been filleted by a radius of 5mm. the command works exactly the same as the chamfer command, except we must specify a radius rather than a distance. we'll go through the process just incase you're unsure: 1) draw a rectangle using the line command, with a size of 50x50. 2) select the fillet button 3) we will specify a radius, so enter r for radius 4) autocad asks for the fillet radius, enter 5 then hit enter the fillet radius is now set. 5) select the first line segment to fillet then hit enter 6) select the second line segment to fillet then hit enter the two lines will have been filleted with a radius of 5 as we specified. repeat the procedure to fillet the remaining 3 corners. as with the chamfer lesson above, we can apply the fillet command to a polyline which will fillet all intersecting lines. while using the fillet command be careful not to specify a radius too large. explode- the explode command is very straightforward. it simply breaks down an object object down to its basic line entities. for example, a rectangle drawn with the rectangle command is drawn as a polyline; the separate lines making the rectangle can't be selected or edited. if we choose the explode button , then select the rectangle object, it will be broken down (or exploded!) into its 4 separate lines. explode can also be used to break apart a block and also hatching (covered later). a basic rule of thumb would be: if you can't select an object you wish to edit, or wish to edit only part of an object, try exploding it to break it down to its basic form of lines and arcs. that concludes our modify tools tutorial. with the modify commands covered in this tutorial, you should be able to create most 2d drawings you would ever need too! (of course - combined with the basic draw tools covered earlier).
lesson 7 layers layers are a way of managing, tidying and also controlling the visual layout of a drawing. a whole section of a drawing can be turned on or off, or simply one aspect can be controlled - text for example. this is all done by using layers within autocad.
the concept of layers is used in other software applications, such as paintshop programs. for those not aware of the concept, we'll start from the beginning: when a new autocad drawing is created, everything which is drawn is drawn on the one default layer, named 0. when creating drawings, the layer 0 shouldn't really be used. new layers should be set up with names corresponding to the content contained on them. what is a layer? a layer can be thought of as a large piece of clear plastic, as infinitely large as the drawing area in autocad. when drawing in autocad, everything is drawn on the default layer which is set current. only the objects you are drawing are visible on the layer, the layer itself can never be seen - it is invisible. each new layer is created by you, the user. normally, it is acceptable to have a layer for each different part of a drawing. the layers created for a simple house plan could be as follows:
wall_external wall_internal doors windows fittings text_notes dimensions the separate lines and shapes representing each part of the house would be arranged on its relevant layer above. each layer could be assigned its own colour so that everything drawn on that layer appeared the same colour. remember we said that layers can be used to manage drawings? well for example, in order to see the drawing more clearly, we may want to remove all the text and dimensions from the drawing. we want to keep the information, just remove it from view. deleting it wouldn't be appropriate as we would lose all of our work! all we have to do is tell autocad to not display the text notes and dimensions layers by turning off the layers in layer manager. the layers can then be turned back on again whenever we choose.
layers are controlled by the layer properties manager button
which is located on the object properties toolbar:
the layer property manager is where all the layers are controlled. the layout above shows a typical use of layers. from the layer property manager we can: add a new layer - press the new button to create a new layer. delete a layer - press the delete button to delete the selected layer. set current layer - press the current button to set the selected layer current. all objects drawn will then be drawn on this current layer. show details - press the show details button to see more detailed information about the selected layer. each layer also has the following options against it:
name - displays the layer name. on - controls if the layer is on or off. select the light bulb to turn the layer off on the drawing. freeze in all vp - pressing this will freeze the layer in all viewports as well as the current model view (see lesson 10 to learn about viewports)
lock - this handy feature locks a layer preventing any content of the layer from being modified. colour - change this to whichever colour you like. all objects drawn on the layer will display the chosen colour provided that the objects colour setting in the object properties toolbar (shown above) is set to 'by layer'. linetype - set the default linetype for all objects drawn on the layer. i.e. continuous, dashed, dotted etc. lineweight - set the thickness a line appears .default is no thickness. this option can be toggled on/off on the display by the lwt button above the command console. plot - select if the layer will be shown when the drawing is plotted (printed). the current layer, layer colour, linetype and lineweight can all be controlled outside of the layer properties manager via the object properties toolbar. that's it for basic layer controls! get used to using layers as you will be using them often - especially when you find you need to start managing large drawing files that contain a lot of information.
lesson 8 text text can be added to an autocad drawing to create notes and labels on your drawings. there are two different text commands used to add text to drawings: text and mtext. the text command is a simple way to add basic text notes. the height and rotation of the text can be quickly specified and the text can be viewed on the drawing while being typed. try adding a small piece of text in a new drawing using the text command: 1) enter the command text into the command console then hit return 2) when prompted for a start point, select somewhere in the screen just left of centre 3) when asked for a height, enter 3 4) when asked for a rotation angle, hit enter to accept the default of 0. 5) now simply enter your text. type: autocad central then hit return to start a new line type: lesson 8 6) hit return twice to exit the text command. the text should be on two separate lines as shown below:
try selecting the text. notice how each line is separately selectable and independent of the previous line? although the text command is simple to use, as each line is separately editable, modifying notes on a drawing can become a nightmare! this text
type is called single line text. multiline text multiline text is the more advanced text tool within autocad. it can be chosen from the 'draw' toolbar by this icon: . the multiline text command has its own editor, with all the options available that you'd expect to see in a word processing program. also, all text on separate lines is treated together, so editing notes and sentences is simple. 1) select the multiline command button 2) we are prompted to select a first corner then second corner. this invisible boundary sets the horizontal extent of the text. when text is entered into the multiline text editor, it will automatically start a second line when it comes to the edge of the text box we specified. similar to getting to the right hand margin in a text editor. select a box roughly a quarter of the drawing area. 3) the multiline text editor then appears:
the main character tab of the text editor box is where we choose the font style, text height, colour and also add symbols such as diameter or degrees symbols. the properties tab is where we can change the text rotation and paragraph justification settings. change the text style to 'arial'. 4) set text height to 3 5) enter the following text into the text editor window: autocad central 6) hit enter for a new line, then enter: lesson 8 7) press the ok button to place the text into the drawing (the text placement will be justified as set in the properties-justification setting in the text editor, relative to the text area box we selected in step 1) notice how when the text is selected, it is treated as one entity rather than separate lines? this makes it much easier and quicker to edit. to edit the text in the drawing area, simply double click the text with the cursor to open up the text editor. text in autocad is treated like every other object, it can be rotated, mirrored, exploded, moved layers etc. when setting the text height, it is important to remember that it is relative to the units you are using. for example, if you decide that 1 autocad unit is equal to a
metre, then setting a text height of 3 would result in 3m high text, and would tower over the drawing! a text size of somewhere around 0.02 would probably be more appropriate. when first using text, a small amount of trial and error is required to get the text height to a suitable size. try to aim for a text height which measures between 2 and 3mm in paperspace for general notes. text can be added to an autocad drawing to create notes and labels on your drawings. there are two different text commands used to add text to drawings: text and mtext. the text command is a simple way to add basic text notes. the height and rotation of the text can be quickly specified and the text can be viewed on the drawing while being typed. try adding a small piece of text in a new drawing using the text command: 1) enter the command text into the command console then hit return 2) when prompted for a start point, select somewhere in the screen just left of centre 3) when asked for a height, enter 3 4) when asked for a rotation angle, hit enter to accept the default of 0. 5) now simply enter your text. type: autocad central then hit return to start a new line type: lesson 8 6) hit return twice to exit the text command. the text should be on two separate lines as shown below:
try selecting the text. notice how each line is separately selectable and independent of the previous line? although the text command is simple to use, as each line is separately editable, modifying notes on a drawing can become a nightmare! this text type is called single line text. multiline text multiline text is the more advanced text tool within autocad. it can be chosen from the 'draw' toolbar by this icon: . the multiline text command has its own editor, with all the options available that you'd expect to see in a word processing program. also, all text on separate lines is treated together, so editing notes and sentences is simple. 1) select the multiline command button 2) we are prompted to select a first corner then second corner. this invisible boundary sets the horizontal extent of the text. when text is entered into the multiline text editor, it will automatically start a second line when it comes to the edge of the text box we specified. similar to getting to the right hand margin in a text editor. select a box roughly a quarter of the drawing area. 3) the multiline text editor then appears:
the main character tab of the text editor box is where we choose the font style, text height, colour and also add symbols such as diameter or degrees symbols. the properties tab is where we can change the text rotation and paragraph justification settings. change the text style to 'arial'. 4) set text height to 3 5) enter the following text into the text editor window: autocad central 6) hit enter for a new line, then enter: lesson 8 7) press the ok button to place the text into the drawing (the text placement will be justified as set in the properties-justification setting in the text editor, relative to the text area box we selected in step 1) notice how when the text is selected, it is treated as one entity rather than separate lines? this makes it much easier and quicker to edit. to edit the text in the drawing area, simply double click the text with the cursor to open up the text editor. text in autocad is treated like every other object; it can be rotated, mirrored, exploded, moved layers etc. when setting the text height, it is important to remember that it is relative to the units you are using. for example, if you decide that 1 autocad unit is equal to a metre, then setting a text height of 3 would result in 3m high text, and would tower over the drawing! a text size of somewhere around 0.02 would probably be more appropriate. when first using text, a small amount of trial and error is required to get the text height to a suitable size. try to aim for a text height which measures between 2 and 3mm in paperspace for general notes.
lesson 9 hatching hatching is used to add shaded patterns to objects and shapes within an autocad drawing. hatch patterns can be used to indicate a material to be used, such as a concrete hatch. alternatively it could be used to make an area of a drawing stand out.
a foundation detail with the autocad default ar-conc hatch pattern applied. the hatch command can be found on the draw toolbar, or the draw drop down menu. when entered, a dialogue box appears as shown below:
type - custom hatch patterns can be created in autocad. leave it set to predefined to use autocad’s built in hatch patterns. pattern - this is where we select a hatch pattern from autocad’s default list. select to view more patterns. the hatch pattern palette appears, with hatch patterns arranged under the categories; ansi', 'iso', 'other predefined' and 'custom'. the most common hatch patterns required are under the 'other predefined' tab. angle - this sets the angle of the hatch pattern, the default value is 0.
scale - this sets the size of the hatch pattern. this must be set correctly dependant on if you are drawing in metres or millimetres. a little trial and error is required to obtain a suitable scale (see preview below). pick points & select objects - these are autocad's two different methods of hatching an area. using pick point, clicking inside an area (such as a rectangle) will result in the hatch pattern being applied to all blank space within the boundary. select object simply hatches within a selected object. great care must be taken to ensure that the area to be hatched is closed, and all line endpoints are meeting each other. if a small gap is left open, the hatch command will fail, usually with the error: unable to hatch boundary. preview - enables a quick preview of the hatch before applying it, letting us quickly change and preview settings before we ok them. very useful when trying different hatch scales. inherit properties - this command enables the hatch settings of a hatch already in use in the drawing to be brought into the boundary hatch dialogue box. composition - this is how autocad is to treat objects to be hatched. for the moment, leave it set to associative. pick point
the above hatch was created by using the pick point method. the hatch stays within all the solid lines. select object
the above hatch was created by using the select object command. the rectangle was selected, and as a result the entire rectangle becomes hatched. interestingly, if both the hexagon and rectangle were selected (i.e. both boundaries) then the hatch pattern would have had the same result as in the above 'pick point' example. be careful to ensure that there are no gaps in the boundary to be selected (zoom in if required). usually, this results in either unexpected results, or a hatch error as shown below.
have a go with the hatch command with the following autocad drawing file: lesson9.dwg (autocad 2000 file) lesson9r14.dwg (autocad 14 file) use the select object method to apply the hatch pattern ar-conc (found in other predefined in the hatch pattern palette) to the concrete foundation. use a hatch scale of 1 and angle 0. use the pick point pattern to apply the hatch pattern ansi32 (found in ansi in the hatch pattern palette) to the bricks. use a hatch scale of 3 and an angle of 0. note: separate multiple areas can be selected with the pick point method, all in one go! your finished drawing should look like the one below:
lesson 10 model space & layout (paper) space there are two drawing areas within an autocad drawing, model space and paper
space. when autocad is loaded, the drawing area which we see is known as model space. all drawing or 'modeling' done within autocad is drawn in model space. the autocad screen tells us we are in model space in the two following locations:
the left hand model tab has two default tabs next to it named 'layout1' and 'layout2'. these are shortcuts to the two default paper space views 'layout1' and 'layout2'. by double clicking the right hand model button shown above, this will take us to the default paper space view layout1. what is paper space? many beginners to autocad get confused about paper space, so we'll try and make it as painless as possible! the concept is in fact very simple! by now you should be familiar with model space, and what it is. to summarize; model space is the main drawing area in autocad. paper space is an area used in autocad to plot (print) the drawing created in model space. paper space is a lot more powerful than simply letting us plot the entire model space drawing; we can set up views called viewports within the paper space area to separately show different areas of the model space drawing. paper space is actually a blank sheet; the separate viewports showing different views of the model are what creates a printable drawing.
the screen shot above shows a paper space layout created named 'a4 layout view paper space 1'. notice how earlier where the screen showed us that we were in model space, it now says paper to indicate paper space. a rectangle measuring 275x200mm was drawn in paper space, so that it would fit nicely on an a4 sized sheet of paper. all autocad commands that are used in model space can be used in paper space, however everything in paper space should be drawn at 1:1 (full size) in millimetres if the drawing is to be printed to scale. the rectangle drawn is simply a frame which will provide a border to the drawing, when plotted. notice how each of the three views of the guitar head are bordered by a black rectangle, these are in fact separate viewports - each looking at the same 3d model in model space, but looking from different angles. think of paper space as the piece of paper you wish to print on to, with holes cut away where you want different parts of the model space drawing to be shown. the model can be moved closer or further away from the hole, and also panned around. the view of the model in one view port is totally independent from the view in another, and zooming into one view port will not affect the view of other viewports within the paper space. practice - using paper space viewports download the autocad drawing file lesson10.dwg, which is the above drawing of a gibson les paul guitar head. the a4 paper space layout has already been created for you. lesson10.dwg (autocad 2000 file) lesson10 r14.dwg (autocad r14 file) 1) the drawing will open in model space, with the guitar head centered within the screen. 2) click the tab next to the 'model' tab which says 'a4 layout view - paper space 1'. this will take us out of model space and into paper space.
the a4 sized rectangle frame with a title block is shown. this was drawn directly onto paper space, just like as if we were drawing in model space. zoom out a little, notice the white box - this is the edge of the a4 sheet when plotted. in paper space, provided your plotter is set to the correct paper size setting, what you see is what you get. generally, what is shown on paper space is what will be plotted. currently, there are no views of the model. we must add a view port to be able to 'see through' the paper space and into model space. 4) under the 'view' drop down menu, go to viewports -> 1 view port. drawing a view port is exactly the same as drawing a rectangle, simply two opposite corners have to be specified. draw a viewport roughly in the centre of the a4 frame, as shown below.
notice how the model is zoomed extents to the viewport. we have now created a viewport within paper space, ready for plotting. working with viewports once a viewport is created, it itself can be modified, and so can its view. to activate a viewport, double click within the viewport window. the cross hair movement is now restricted to the viewport window. the bottom status bar will now indicate that we have entered model space, although we are still in paper space. effectively, we are in model space, but working in model space through paper space. to exit out of the viewport, simply double click out of the viewport (or double click the status bar at the bottom of the screen to toggle between model/paper space). once a viewport is created, its contents can be changed by activating it, and zooming/panning throughout the drawing to change the view. we can even work on the model through paper space, as all the usual commands are still active .a viewport can be moved around in paper space using the move command, however a viewport cannot be rotated. to change the size of a viewport, select it while in paper space, and change its size by dragging the blue grips at each corner of the viewport. to hide the rectangular frame of a viewport, simply create a new layer, turn the layer off then add the viewport to the layer. the viewport frame will then become invisible, although the viewport still functions. of course, when you want to move/resize the viewport, don't forget to turn the layer back on! plotting to scale to be able to plot an autocad drawing to scale, we need to set the zoom factor within
the viewport. setting the zoom factor enables us to fix the scale of the viewport when plotting from paper space at 1:1 (not scale to fit!). to set a viewport to a scale is a simple procedure, we simply need to recognize if within model space we decided to draw in metres or millimetres i.e. does one autocad unit represent 1mm or 1m? the zoom factor of a drawing is known as its xp value, and the xp value is determined as below (if one autocad unit represents 1m): xp value (m) = 1000/scale required example: viewport scale required = 1:200 xp value = 1000/200 = 5 zoom factor = 5xp if the model is drawn that 1 autocad unit represents 1mm, then the above formula applies, but the zoom factor must then be divided by 1000. xp value (mm) = (1000/scale required) / 1000 example: viewport scale required = 1:200 xp value = ( 1000/200 ) / 1000 = 5/1000 = 0.005 zoom factor = 0.005xp the table below summarizes the xp zoom scale factors for the common scales:
don't forget that within paper space, we can have as many viewports as we like (although the more viewports active, the more pc memory is used which can affect your system's performance). plotting now that we know how to set up a paper space view with scaled viewports, we simply have to plot it to a printer for a true scale, paper copy of the drawing. printing from autocad is simple, we just have to ensure that a few settings are correct. to open the plot menu, click the plot icon on the standard toolbar, or select 'plot' from the file drop down menu. the plot dialogue box will appear:
first of all, click the 'plot device' tab to select the printer you wish to plot to:
the printer can be selected from the drop down list, the properties of the printer can also be selected to change print quality e.t.c. plot style is where we can choose the colour of the plot, based on the on-screen colours. for example, every red line within autocad can be set to print red, or could be set to print out black. this setting can be left as none for now. full preview is where we can preview the print, but only after we have chosen our plot setup in 'plot settings'. partial preview provides a simplified preview of the drawing, useful for previewing large drawings which would take a while to regenerate all the viewports for the preview.
back to the 'plot settings' tab:
paper size - select the paper size of the print out (this will usually be the size of the frame drawn in paper space. in the case of the lesson10.dwg tutorial file, this should be set to a4. drawing orientation - simply landscape or portrait. for this example set it to landscape, to match the paper space layout. plot scale - this is where the entire paper space scale is set. remember earlier when we said that everything in paper space should be drawing in millimetres at 1:1 full size? for the print to plot to scale, plot scale must be set to 1:1. if a quick 'not to scale' plot is required of a drawing (or part of a drawing - see plot area below) the plot scale can be set to 'scaled to fit' to fill the paper with the selected print area. plot area - we must select which part of the drawing we wish to plot. in this case, we wish to plot the entire a4 frame in paper space: layout - this will plot the current layout. extents - similar to zoom extents. the extents of the paper space area will be plotted. display - the current screen display will be plotted. window - this is the most useful tool to select the plot area. similar to zoom window, plot window allows us to select the exact area to be plotted by selecting a rectangle around the required area. select the window radio button, then click the 'window< ' box to select the window area. choose the top left then bottom right corners of the blue a4 frame in paper space. plot offset - this enables us to select the position of the plot on the paper. for best results, select 'centre the plot' to plot the drawing central to the paper sheet. plot options - these settings can be left as they are.
now that we have defined our plot settings, go back to the 'plot device' tab and select 'full preview' to see a preview of the print job. it should be similar to the screen shot below:
finally, to exit the preview, right click and select exit. this takes us back to the plot dialogue box. go back to the 'plot settings' tab and select the 'plot' button to send the drawing to the printer.
lesson 11 object snap object snap tools are available from the object snap toolbar (view - toolbars to enable). they allow for precise drawing within autocad. for example, a rectangle could be drawn from the exact endpoint of an existing line by simply selecting the 'snap to endpoint' tool, or we could draw a line from the centre point of a circle using the 'snap to center' tool. in many cases, object snap avoids the need to draw construction lines, thus making it quicker and easier to create precise, accurate drawings.
the first point of the rectangle above was drawn from the endpoint of the 45 degree line. the object snap tools can be used whenever a point has to be defined, which is in nearly every drawing command used! when we use the snap tools, a yellow marker will appear when the cursor is near a suitable snap point. a single left click of the mouse will automatically select the marked point. snap tools from left to right on the above toolbar screen shot (note: dependant on your version of autocad, some snap settings may not be available). snap to endpoint - this will select the endpoint of any line or polyline segment. also works on 'closed' objects such as rectangles. snap to midpoint - very handy tool. this will select the mid-point of any line segment. snap to intersection - selects the exact point at which two lines cross. snap to apparent intersection - similar to above, although the lines don't have to intersect. this snap requires you to select a line, then hover the cursor over any other line, the marker will let you select the point where the two lines would intersect if they were extended. snap to extension - this snap tool enables you to select a point along the same orientation as an existing line, with a handy readout of the angle and position of the point (see screen shot below).
snap to center - this handy snap function selects the perfect centre of an existing circle. even more impressive however is that the centurion of an arc or semi-circle can also be selected.
snap to quadrant - snap to the four quadrant points of a circle (top, bottom, left and right). snap to tangent - as it says, snaps to the tangent point of an arc.
snap to perpendicular - snaps to the perpendicular point on an object from the original start point. pretty straightforward, and very useful. snap to parallel - snaps parallel to a specified line. snap to insert - snaps to the insert point of an object, such as an inserted block. not really that useful. snap to node - snaps to points drawn using the point command. snap to nearest - should be called snap to anything! quite literally will snap to anywhere along any length of any object. can be useful though while 'sketching' with autocad, or perhaps laying down a few construction lines. object snap settings - snap settings. object snap can be toggled to be permanently on or off via the osnap tab situated to the bottom of the cad window above the windows start menu. alternatively simply press f3 to toggle. to change which snap functions are to be used, either right click the osnap tab and select 'settings', or select the object snap settings button from the object snap toolbar.
blocks a block in autocad is a collection of all of the line and arc entities that create an object, 'molded' together to make one selectable object. selecting one particular entity (such as a midpoint of a line for example) will select all objects contained within the block. they can be moved, rotated, mirrored etc and will always be treated
by autocad as one whole object. the only way to 'break' the block apart, and split it into its separate line entities, is to explode it. if one particular part of a block needs to be changed, the block has to be exploded, the modification made, and the objects created back into a block. why use blocks? blocks are an invaluable way of quickly arranging complex pieces of a drawing. selecting the object is a breeze; it is no longer necessary to painstakingly select each individual line. they also prevent accidental modification of parts of the object, as they cannot be modified unless the whole block has been exploded. blocks also make it easy to duplicate the same object throughout a drawing, and as autocad recognizes that each copy of a block is identical to the previous, the memory & processing time required by autocad is reduced. the most impressive feature of blocks is that if a block detail has to be amended, simply changing the detail and 'redefining' the block applies the changes to every instance of the block in the drawing! block example a simple example of the use of blocks is in a plan view of a classroom measuring 5.5m x 5.5m. you may be required to find the most suitable layout for 12 desks and 24 chairs. you would of course have to draw the chair and table. then simply turn them each into a block. they can then be moved, selected and copied simply and quickly. 1) download the drawing file for your version of autocad. classroom.dwg autocad 2000 .dwg file classroom r14.dwg autocad 14 .dwg file 2) firstly we'll turn the table into a block. to open the 'block definition' box type the command block into the autocad console then hit return.
3) we'll need to name the new block that we create. type chair into the name box. 4) click the select objects button to select the separate entities that we wish to contain within the block. select all lines making the table then right-click or hit enter to return to the block definition box. within the objects section we have 3 options to choose from: retain, convert to block and delete. retain: once the ok button is hit, the block will be created and stored within the drawing, although the selected entities will not have been turned into the block and will be kept as separate entities. the block can be inserted from the 'insert -> block ' drop down menu. convert to block: this is the opposite of retain, the selected entities will be converted into a block, and will be the first instance of the block within the drawing. delete: not as drastic as it sounds! the block will be created, although not displayed. the seperate entities which make the block will be deleted. the block can be inserted from the 'insert -> block ' drop down menu. in this instance, choose convert to block. 5) now we hace to choose a base point for the block. this is simply the insertion point if we decide later to insert the block from insert-> block in the drop down menus. choose a suitable position, such as the approximate centre of the table, or the midpoint of one of the lengths. right-click or hit enter to return to the block definition box. 6) preview icon simply lets you choose if you want autocad to create a small preview of the block which will be shown in the insert block box. this function is useful if a large amount of blocks are to be created within a drawing. whichever option is chosen does not affect the block creation, so choose whichever option you prefer! 7) insert units should be set to whichever scale we you are drawing in. this drawing is using 1 autocad unit to represent 1mm, so select millimetres from the drop down
box. an optional description of the block can be entered, if desired. 8) that's it! hit ok to create the block. try selecting the table, notice how the entire table becomes selected? also note that the colour and linetype of any of the lines within the table cannot be edited. now turn the drawing of the chair into a block using the block command, name the block: chair, and use the convert to block option. now that we have the chair and table block, let’s see how simple it is to work with blocks. 1) copy the chair and place the copy to the right of the existing chair, so that that there are two chairs behind the table.
remember how we said we would arrange the 12 tables and 24 chairs to fit into the room? let’s arrange them by making copies of the original blocks. it would be acceptable to use the copy command to make copies, although it may be a little tiresome to arrange them neatly. by far the quickest way is by using the array command we looked into in tutorial 6. use an offset of 1500mm for the row and column offsets, and array to 4 rows and 3 columns as shown below.
the finished result:
redefine the block imagine that the school decides that the chairs aren't to have arms! all of the chairs can be amended by simply exploding 1 chair, modifying it then saving back to the block using the same block name: 1) zoom in on one of the chairs, and explode it. this will break the block. 2) delete the arms of the chair, as below.
3) now use the block command to turn the 'armless' chair back into a block. make sure that you use the same block name as the existing block to be changed, for block redefine to work correctly. 4) autocad will warn you: 'chair is already defined. do you want to redefine it?’ choose yes. voila! every instance of the chair has now been changed by redefining the block. this is where the power of creating blocks really comes into its own. wherever your are copying the same information around in a drawing, always ensure that you have turned it into a block first, it can save a lot of headache when you later decide to alter the original detail!