Acme Thread-Inch En
Short Description
With clearance on all diameters for free movement, general purpose Acmes are used for a wide variety of parts including ...
Description
General Purpose Acme Thread With clearance on all diameters for free movement, general purpose Acmes are used for a wide variety of parts including all types of vise and jack screws where holding major diameter is not a critical consideration. Three classes of thread fit tolerances are available: 2G, 3G and 4G. Basic Acme dimensions are given in accompanying tables.
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Page 1/6
ACME FORM BASIC DIMENSIONS (Inch) Depth of thread (basic)
Total depth
Width of flat
Thread
of thread
thickness
(all
(basic)
screws)
Crest of nut (basic)
45º chamfer, crest of diameter of
Maximum
Fillet radius at minor diameter of
Width of flat centralizing screws
fillet radius
centralizing screws
root of Root
Minimum
Minimum width of
centralizing
of nut
depth
flat
tapped hole
Minimum classes 5 and 6 only, 0.07P
Minimum all classes , 0.10P
0.03 0.0312 125 5
0.03 0.0362 62
0.03 0.0312 125 5
0.02 0.0232 32
0.02 0.0206 06
0.00 0.0031 31
0.00 0.0044 44
0.00 0.004 4
0.00 0.0044 44
0.00 0.0062 62
0.03 0.0357 571 1
0.04 0.0407 07
0.03 0.0357 571 1
0.02 0.0265 65
0.02 0.0239 39
0.00 0.0036 36
0.00 0.005 5
0.00 0.004 4
0.00 0.0050 50
0.00 0.0071 71
0.04 0.0416 167 7
0.04 0.0467 67
0.04 0.0416 167 7
0.03 0.0309 09
0.02 0.0283 83
0.00 0.0042 42
0.00 0.006 6
0.00 0.005 5
0.00 0.0058 58
0.00 0.0083 83
0.05 0.0500 000 0
0.06 0.0600 00
0.05 0.0500 000 0
0.03 0.0371 71
0.03 0.0319 19
0.00 0.0050 50
0.00 0.007 7
0.00 0.006 6
0.00 0.0070 70
0.01 0.0100 00
0.06 0.0625 250 0
0.07 0.0725 25
0.06 0.0625 250 0
0.04 0.0463 63
0.04 0.0411 11
0.00 0.0062 62
0.00 0.009 9
0.00 0.0075 75
0.00 0.0088 88
0.01 0.0125 25
0.08 0.0833 333 3
0.09 0.0933 33
0.08 0.0833 333 3
0.06 0.0618 18
0.05 0.0566 66
0.00 0.0083 83
0.01 0.012 2
0.01 0.010 0
0.01 0.0177 77
0.01 0.0167 67
0.10 0.1000 000 0
0.11 0.1100 00
0.10 0.1000 000 0
0.07 0.0741 41
0.06 0.0689 89
0.01 0.0100 00
0.01 0.014 4
0.01 0.012 2
0.01 0.0140 40
0.02 0.0200 00
0.12 0.1250 500 0
0.13 0.1350 50
0.12 0.1250 500 0
0.09 0.0927 27
0.08 0.0875 75
0.01 0.0125 25
0.01 0.018 8
0.01 0.015 5
0.01 0.0175 75
0.02 0.0250 50
0.16 0.1666 667 7
0.17 0.1767 67
0.16 0.1666 667 7
0.12 0.1236 36
0.11 0.1184 84
0.01 0.0167 67
0.02 0.024 4
0.02 0.020 0
0.02 0.0233 33
0.03 0.0333 33
0.20 0.2000 000 0
0.21 0.2100 00
0.20 0.2000 000 0
0.14 0.1483 83
0.14 0.1431 31
0.02 0.0200 00
0.02 0.028 8
0.02 0.024 4
0.02 0.0280 80
0.04 0.0400 00
0.25 0.2500 000 0
0.26 0.2600 00
0.25 0.2500 000 0
0.18 0.1853 53
0.18 0.1802 02
0.02 0.0250 50
0.03 0.035 5
0.03 0.030 0
0.03 0.0350 50
0.05 0.0500 00
Centralizing Acme Screw Rod Centralizing Acmes have limited clearance at the major diameter of screw and nut and are used extensively for feed screws. The limited clearance enables a bearing at the major diameter to maintain alignment of the thread axis preventing wedging on the flanks and part sagging. Five classes are used: 2C, 3C, 4C, 5C, and 6C. Classes 5C and 6C are designed to allow limited backlash, though some backlash will be experienced with any of these classes. Differences between General Purpose and Centralizing threads are found by referring to the limiting dimensions and tolerances. For example, while a 1/2" diameter, 10 pitch Class 3 General Purpose thread has a 0.5000" 0. 5000" maximum major diameter and .4950" minimum for a tolerance of 0.0050" - the similar Centralizing Acme has a 0.5000" major O.D. and a minimum major of .4989" for f or a major diameter tolerance of just .0011". Tolerances Tolerances for the pitch and minor diameters are the same for both General Purpose and Centralizing Acmes Acmes of the same diameter and pitch. Page 2/6
GENERAL PURPOSE AND CENTRALIZING ACME TOLERANCES (Inch) Basic diameters Identification
General purpose and centralizing classes 2,3, and 4
Nominal sizes (all classes) 1/4
Thread data Centralizing, classes 5 and 6
Threads
Major
Pitch
Minor
Major
Pitch
Minor
Per Inch.
diameter
diameter
diameter
diameter
diameter
diameter
16
0.2500
0.2188
0.1875
*
*
*
Pitch 0.06250
Thread
Basic
Basic
thickness
depth of
width of
at pitch
thread
flat
0.03152
0.03125
0.0232
5/16
14
0.3125
0.2768
0.2411
*
*
*
0.07143
0.03571
0.03571
0.0265
3/8
12
0.3750
0.3333
0.2917
*
*
*
0.08333
0.04167
0.04167
0.0309
7/16
12
0.4375
0.3958
0.3542
*
*
*
0.08333
0.04167
0.04167
0.0309
1/2
10
0.5000
0.4500
0.4000
0.4823
0.4323
0.3823
0.10000
0.05000
0.05000
0.0371
5/8
8
0.6250
0.5265
0.5000
0.6052
0.5427
0.4802
0.12500
0.06250
0.06250
0.0463
3/4
6
0.7500
0.6667
0.5833
0.7284
0.6451
0.5617
0.16667
0.08333
0.08333
0.0618
7/8
6
0.8750
0.7917
0.7083
0.8516
0.7683
0.6849
0.16667
0.08333
0.08333
0.0618
1
5
1.0000
0.9000
0.8000
0.9750
0.8750
0.7750
0.20000
0.10000
0.10000
0.0741
1-1/8
5
1.1250
1.0250
0.9250
1.0985
0.9985
0.8985
0.20000
0.10000
0.10000
0.0741
1-1/4
5
1.2500
1.1500
1.0500
1.2220
1.2220
1.1200
0.20000
0.10000
0.10000
0.0741
1-3/8
4
1.3750
1.2500
1.1250
1.3457
1.2207
1.0957
0.25000
0.12500
0.12500
0.0927
1-1/2
4
1.5000
1.3750
1.2500
1.4694
1.3444
1.2194
0.25000
0.12500
0.12500
0.0927
1-3/4
4
1.7500
1.6250
1.5000
1.7169
1.5919
1.4669
0.25000
0.12500
0.12500
0.0927
2
4
2.0000
1.8750
1.7500
1.9646
1.8396
1.7146
0.25000
0.12500
0.12500
0.0927
2-1/4
3
2.2500
2.0833
1.9167
2.2125
2.0458
1.8792
0.33333
0.16667
0.16667
0.1236
2-1/2
3
2.5000
2.3333
2.1667
2.4605
2.2938
2.1272
0.33330
0.16667
0.16667
0.1236
2-3/4
3
2.7500
2.5833
2.4167
2.7085
2.5418
2.3752
0.33333
0.16667
0.16667
0.1236
3
2
3.0000
2.7500
2.5000
2.9567
2.7067
2.4567
0.50000
0.25000
0.25000
0.1853
4
2
4.0000
3.7500
3.5000
3.9500
3.7000
3.4500
0.50000
0.25000
0.25000
0.1853
5
2
5.0000
4.7500
4.5000
4.9441
4.6941
4.4441
0.50000
0.25000
0.25000
0.1853
Page 3/6
Standard
Stub” Acme
Originally derived from the General Purpose form, the Stub Acme is generally used for applications where a coarse pitch thread of shallow depth must be used due to mechanical or metallurgical considerations. What would a typical Stub Acme be used for? A standard 1-1/2 - 5P Acme is planned for a part, but the amount of metal removal would reduce the minor diameter to the point where the torque would twist the part. The solution: use a 1-1/2", 5 pitch two start, or 1-1/2", 5 pitch Stub Acme. Thread height for Standard Stub Acmes is equal to 0.3 times the pitch, while the height of a Standard Acme is 1/2 of the pitch. Otherwise, the forms are identical.
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Page 4/6
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STANDARD STUB ACME THREAD FORM, BASIC DIMENSIONS (Inch) Threads Per Inch
Pitch
Height of thread
Total height Thread
Thread thickness,
(basic), h=0.3p
hs=ht,(basic), t=p/2
(basic), t=p/2
Crest of internal thread (basic),F=0.4224p
Root of internal thread Frn=0.4224p-0.259 x allowance
16
0.0625
0.0188
0.0238
0.03125
0.0264
0.0238
14
0.0714
0.0214
0.0264
0.35710
0.0302
0.0276
12
0.0833
0.0250
0.0300
0.04167
0.0352
0.0326
10
0.1000
0.0300
0.0400
0.05000
0.0422
0.0370
9
0.1111
0.0333
0.0433
0.05556
0.0469
0.0417
8
0.1250
0.0375
0.0475
0.06250
0.0528
0.0476
7
0.1429
0.0429
0.0529
0.07143
0.0603
0.0551
6
0.1667
0.0500
0.0600
0.08333
0.0704
0.0652
5
0.2000
0.0600
0.0700
0.10000
0.0845
0.0793
4
0.2500
0.0750
0.0850
0.12500
0.1056
0.1004
3-1/2
0.2857
0.0857
0.0957
0.14286
0.1207
0.1155
3
0.3333
0.1000
0.1100
0.16667
0.1408
0.1356
2-1/2
0.4000
0.1200
0.1300
0.20000
0.1690
0.1638
2
0.5000
0.1500
0.1600
0.25000
0.2112
0.2060
1-1/2
0.6667
0.2000
0.2100
0.33333
0.2816
0.2764
1-1/3
0.7500
0.2250
0.2350
0.37500
0.3168
0.3116
1
1.0000
0.3000
0.3100
0.50000
0.4224
0.4172
Page5/6
Modified Stub Acme Threads For Modified Form 1, (M1) - the pitch and minor diameters will be smaller than similar values for the standard form. For Modified Form 2, (M2) - the pitch and minor diameters will be larger than the values for the standard form. M1 AND M2 STUB ACME THREAD FORMS, BASIC DIMENSIONS (Inch) M1 STUB ACME
M2 STUB ACME Width of flat
Height of
Threads Per
Pitch
Inch
thread (basic), h=0.375p
Total height of thread hs=h+1/2allowance
Thread
at crest of
thickness
internal
(basic),
thread
t=1/2p
(basic),
Width of Height of
Threads Per
Pitch
Inch
thread (basic), h=0.250p
Total height of thread, hs=h+1/2allowance
Thread
flat at crest
thickness
of internal
(basic),
thread
t=1/2p
(basic),
Fcn=0.4030p
Fcn=0.353p
16
0.06250
0.02344
0.0284
0.03125
0.0252
16
0.06250
0.01563
0.0206
0.03125
0.02720
14
0.07143
0.02679
0.0318
0.03572
0.0288
14
0.07143
0.01786
0.0229
0.03571
0.03110
12
0.08333
0.03125
0.0363
0.04167
0.0336
12
0.08333
0.02083
0.0258
0.04167
0.03630
10
0.10000
0.03750
0.0475
0.05000
0.0403
10
0.10000
0.02500
0.0350
0.50000
0.04350
9
0.11111
0.04167
0.0517
0.05556
0.0448
9
0.11111
0.02778
0.0378
0.05556
0.04840
8
0.12500
0.04688
0.0569
0.06250
0.0504
8
0.12500
0.03125
0.0413
0.06250
0.05440
7
0.14286
0.05357
0.0636
0.07143
0.0576
7
0.14286
0.03571
0.0457
0.07143
0.06220
6
0.16667
0.06250
0.0725
0.08333
0.0672
6
0.16667
0.04167
0.0517
0.83330
0.07260
5
0.20000
0.07500
0.0850
0.10000
0.0806
5
0.20000
0.05000
0.0600
0.10000
0.08710
4
0.02500
0.09375
0.1038
0.12500
0.1008
4
0.25000
0.06250
0.0725
0.12500
0.10880
3-1/2
0.28571
0.10714
0.1171
0.14286
0.1151
3-1/2
0.28571
0.71430
0.0814
0.14286
0.12440
3
0.33333
0.12500
0.1350
0.16667
0.1343
3
0.33333
0.08333
0.0933
0.16667
0.14510
2-1/2
0.40000
0.15000
0.1600
0.20000
0.1612
2-1/2
0.40000
0.10000
0.1100
0.20000
0.17410
2
0.50000
0.18750
0.1975
0.25000
0.2015
2
0.50000
0.12500
0.1350
0.25000
0.21770
1-1/2
0.66667
0.25000
0.2600
0.33333
0.2687
1-1/2
0.66667
0.16667
0.1767
0.33333
0.29020
1-1/3
0.75000
0.28125
0.2913
0.37500
0.3023
1-1/3
0.75000
0.18750
0.1975
0.37500
0.32650
1
1.00000
0.37500
0.3850
0.50000
0.4030
1
1.00000
0.25000
0.2600
0.50000
0.43530
Page 6/6
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