AK Receiver Bending

AK Receiver Bending From a Tapco Flat

A tutorial by 1952Sniper  February 2006

(originally posted on http://www.ssboards.!o" http://www.ssboards.!o" by  by 1952Sniper# $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ % de!ided to write this this tutorial a&ter ha'ing spent a day and a hal& bending re!ei'ers. re!ei'ers. %t "ight be a help to those o& you you who are interested in bending your your own re!ei'ers &ro" a &lat. &lat. ysel& and another &oru" "e"ber (%)ll let hi" !hi"e in i& he wants to identi&y hi"sel&# did a whole pro'erbial s***$load o& the"+ and % now now "ore about the pro!ess than % e'er wanted to+ ,-,. % won)t pretend it)s the be$all end$all o& bending re!ei'ers. re!ei'ers. %t)s ust "y "y eperien!e+ and a good starting  point. ou guys that ha'e used other "ethods and other bending &itures+ &eel &ree to !hi"e in and add in&o. For starters+ it)s a lot o& &un. &un. %& you)re only bending a !ouple+ it)s a relati'ely si"ple tas that should tae no ti"e at all. %& you)re doing as "any as we did+ though+ it)s a lot o& wor and needs to be well  planned. ou should !ount on &atigue be!o"ing an issue. i'e yoursel& plenty o& ti"e &or breas. And be aware o& when you)re getting getting tired+ be!ause that)s when a!!idents start start to happen. e ha'e the hand inuries and sore li"bs to pro'e it. 3he pro!ess we used too right at 15 "inutes to go &ro" a &lat to a bent re!ei'er+ &ro" start to &inish. 4ut we a'eraged about  re!ei'ers &or &or e'ery  hours spent. 3hat in!ludes breas+ re$organi7ing tools+ tools+  periodi! !leanup+ et!.+ without &eeling lie we had to rush so "u!h that our 8uality le'el had to su&&er. 4ending a &lat into a re!ei'er should shou ld generally re8uire the &ollowing steps: 1. Asse"ble the inside die around the &lat 2. rease the hell out o& e'erything e' erything . ress it into the outer &or" . S8uee7e the asse"bly in a 'ise to eli"inate possible bowing in the "iddle 5. ;a""er or otherwise bend o'er the upper rails 6. %n'ert the asse"bly and no! out the inside die and re!ei'er  building board+ and is based on the ernelrin design (&or those o& you who are &a"iliar with that userna"e#. userna"e#. %t wors great and is robust enough to last through a lot o& bends. 4elow is a pi!ture o& the inside &or" (the die# and its asso!iated pie!es+ net to one o& the 3ap!o &lats we were about to bend. %)ll apologi7e in ad'an!e &or the !rappy pi!tures. % had to use "y old old digital !a"era be!ause "y good one was out o& ui!e and % !ouldn)t &ind the !harger. Anyway+ in the pi!ture below you you !an see the upper part o& the die+ the lower plate that sandwi!hes the &lat inside+  bo lts that !la"p it all together+ and two aligner pins with  brass nobs on the".

%)ll also pause here to gi'e !redit to the gentle"an that built this  bending &iture and sold it to "e. ;e has "ore "ore &or sale sale and is an etre"ely help&ul and &riendly guy. oes by the userna"e s"ittyg o'er on gun!o.net+ and he has epressed interest in selling the" on this  board too. %n &a!t+ % see that he)s a "e"ber here. So loo &or &or a  post &ro" hi" in the trade/sale &oru"s. ;is bending &iture wored well &or "e and although % ha'en)t used any other types+ % will will say that this this one "ore than "et "y needs. % now se'eral o& you you A> builders are looing &or a bending &iture+ and % !an tell you that s"ittyg will do his best to "ae sure you)re satis&ied satis&ied and answer any 8uestions you you ha'e. Support &or a sold produ!t produ!t goes a long way with "e+ and he)ll de&initely de&initely gi'e support &or his his produ!t. And by the way+ %)" not being being paid &or endorsing his bending &iture. % ust thin he)s got a good produ!t at a good pri!e+ and pro'ides good ser'i!e. A? all around+ around+ and % highly re!o""end his bending &iture.

Step 1: Assemble the die around the flat

-n this parti!ular bending &iture design+ you install the aligner pins through the botto" o& the  botto" plate+ then through the aligner holes on the &lat (whi!h are the s"all holes at the 'ery &ront and rear o& the &lat#. 3his is then lined up with the botto" o& the die+ and the aligner pins are inserted there as well. All   pie!es will be lined up  per&e!tly. @o "easuring or &iddling ne!essary. 3he bolts bolts are then inserted through the top o& the die and they are threaded into the the botto" plate. %t)s i"portant to tighten these bolts &airly tight to ensure that the &lat stays put. 3he  bolts rea!h through the eisting openings in the &lat (the pistol grip s!rew hole+ the trigger hole+ and two through the "ag well opening#. 3hey si"ply draw the botto" plate tight to the die. 3hen the aligner pins are re"o'ed. -n!e the aligner pins are re"o'ed+ re"o'ed+ the only thing holding the &lat in align"ent is the !o"pression o& the bolts. bolts. So tor8ue the" down pretty good+ but not tight enough to strip strip threads. ust a &ir" tug with a so!et wren!h is what % did. hen you get the botto" plate on with the &lat installed+ it loos lie this:

 @ote that you !an see the botto"s o& the  bolts+ and the aligner pins are still in pla!e. 3his botto"  plate ser'es se'eral &un!tions as &ar as % !an tell. tell. %t eeps the botto" o& the &lat positioned properly. %t also eeps the botto" &ro" bowing out when the sides are bent+ gi'ing ni!e !risp !orners. %t also ser'es as a guide inside the &or" as it)s pressed in. in. 3he width o& the botto" plate is the sa"e as the width o& the outside o& your re!ei'er a&ter bending. So the re!ei'er walls B&ollowB the botto" plate into the ig.

Step 2: Grease all contact surfaces of the bending fiture

A&ter the aligner pins are re"o'ed+ you)ll want to grease the hell out o& the botto" o& the &lat+ where it will BrideB the the outside &or" when it)s being being bended. e used obil 1 syntheti! grease. %t)s red in in !olor+ as you you !an see below. -thers use ale grease or other inds o& grease. hate'er &loats your your  boat. ust "ae sure it)s a good 8uality grease that lubri!ates well. well.

And here)s a pi!ture o& the top o& the die with the &lat installed. %t is i"portant to ,%;3, grease the !onta!t sur&a!es  between the inside die and the inside o& the re!ei'er. -therwise you !ould ha'e a hell o& a ti"e getting the re!ei'er o&& o& it later a&ter it)s been bent around all  !orners o& the die. % only tried it on!e without grease on the inside o& the re!ei'er+ and had a hard ti"e. So % !ontinued to grease it and didn)t ha'e any "ore proble"s. 4ut do it lightly+ so it isn)t so"ething that)s ha'ing to be s8uee7ed out when you press the die into the outside &or".

%)ll also tae this opportunity to point out the inletting on the die &or the "aga7ine stabili7er di"ples+ and note that they)re slotted so the di"ples !an ride in that !hannel later+ as you re"o'e the !o"pleted re!ei'er &ro" the die. die. 3his die also had an inletted inletted area &or the di"ple di"ple at the sele!tor le'er. %t did not ha'e any inletting &or the C$ ais di"ples or the sele!tor le'er not!h or the bulge around the le&t side sele!tor sele!tor le'er hole. 3he new 3ap!o &lats ha'e all these di"ples on the"+ but they didn)t see" to be a&&e!ted in the bending pro!ess and they &ared ust &ine. So+ be&ore "o'ing on to the third third step+ you)ll want to grease the outside &or" as well. @ot only on top where the &lat will !onta!t it when you start bending+ but espe!ially at the !orners o& the &or" that "ae the &old+ as well as the inside &a!e. 3his is the "ost "ost !riti!al area. %& it)s not greased greased su&&i!iently+

you will get s!arring on the outside o& your re!ei'er as it slides down inside the &or". ou !an see that % ha'e the top and insides o& the &or" greased+ with the asse"bled die sitting upside down+ ready to be &lipped o'er and pla!ed into it. 3oo "u!h grease is better than not enough. 4e generous.

Step !: Bend the sides of the flat up

la!e the asse"bled die into the top o& the outside &or" and !enter it in the &or" so you)re not too !lose to the ends. 3hen !enter the entire entire asse"bly under the ra". =ouble !he! that your your aligner  pins are re"o'ed and that e'erything is ready to go.

 @ow snug up the ra" to the top+ and start pressing down. %& it)s it)s !entered !orre!tly+ both sides should start to &old up at the sa"e rate+ as you see below.

So"eti"es the sides will gently &old up &lush to the die+ but in "ost !ases % &ound that they would rea!h a point where they BsnapB to the sides+ and the whole shop press goes SD-%@E 3hat)s &ine. ust be aware o& this+ and go slowly when it)s !lose to the  point. As you pro!eed &urther+ the sides should be straight up 'erti!ally in the &or"+ tight against the inside die.

>eep pressing it down into the &or" until the top o& the die is at least &lush with the top o& the outside &or". So"eti"es+ as the die is pressed in+ one end will tend tend to go down &aster &aster than the other. % ept sear!hing &or a Bsweet spotB on the top o& the die that would ensure en sure e'en plunging lengthwise+ but ea!h &lat would go in di&&erently. %& one end sins down &irst+ you)ll need to reposition the ra" to try to get the other side side down. ith this parti!ular parti!ular bending &iture+ the bolt heads on top presented a  proble". % didn)t want to be pressing on the bolt heads+ so % had li"ited roo" between the "iddle  bolts in whi!h to pla!e the ra". hen one end would sin &aster than the other+ we would ha'e to  pull the entire asse"bly and turn it 90 degrees so the ra" !ould get all the way to the end o& the die (the shop press &ra"e wasn)t wide enough to si"ply shi&t the &iture to the side &ar enough#. So then+  pressing on the end o& the die and using a pie!e o& bar sto! to shi" up and ensure that the ra" wasn)t tou!hing a bolt head+ we !ould press the high end down into the &or". &or". %t was a si"ple si"ple enough way to do it and wored well. %n the pi!ture below+ you)ll you)ll see what %)" taling about. %n this !ase+ the die die went into the &or" e'enly. e'enly. 4ut sin!e the rear o& the re!ei'er is taller than the &ront+ it be!o"es ob'ious that the rear end o& the die needs to go down &urther into the &or" than the &ront. So that)s what we)re doing doing here+ trying to get it so the top o& our bent re!ei'er is e'en.

As % said+ ea!h &lat would go into the &or" di&&erently. So"eti"es+ when one end was riding high and we)d go to press that end in+ the other end would start li&ting ba! up slightly. -ther ti"es ti"es it wouldn)t. ust  play it by ear and adust your ra" position as ne!essary to get the die down into the &or". %t really goes pretty 8ui!ly+ so don)t start thining this is a "aor deal. -n!e the die is pressed down with the top !orners about &lush with the outside &or"+ it)s good to go. 3ae it out o& the press.

Step ": #ompress the sides of the form

=epending on the design o& your outside &or"+ you "ay eperien!e bowing in the "iddle during the  pressing operation. % did noti!e a s"all gap in ours+ right at the "iddle o& the re!ei'er. And % "ean s"all lie perhaps a !ouple thousandths o& an in!h. So"e designs "ay not ha'e a noti!eable gap+ but %)d bet you would &ind that it bowed in the "iddle i& you too detailed "easure"ents. %t)s sa&e to assu"e that all &or"s will bow. So the easiest thing to do is ust tae your entire asse"bly asse"bly with the die still in it+ and s8uee7e it tightly in a 'ise to !o"press the sides and sharpen up your botto" !orners o& your your re!ei'er. ou)ll see any gaps !lose right up+ and the grease will s8uee7e out. 3hat "eans it)s good to go.

Step $: Bend the upper rails

3here are 'arious ways o& doing this. So"e bending &itures are sold with an a!!essory that uses the  press to &old the top rails o'er. So"e people si"ply ha""er the" o'er with a ha""er+ woring &ro" one end to the other and then s"a!ing on top o& the die on!e the rails are &olded o'er+ to get out the lu"ps. y partner !a"e !a"e up with the Bworing barB as a great way to ha""er the upper rails o'er without lu"ps. And it wored lie a !ha"p. %t)s ust a long pie!e o& &lat bar with handles welded to it. it. ou ha""er on the woring bar and it translates the &or!e to the rails in a uni&or" "anner to get ni!e s"ooth bends with !risp !orners. 3his re8uires two people. -ne  person stands on one side o& the ben!h 'ise and holds the woring bar by the handles so that it)s al"ost &lat on top o& the outside &or"+ with one side o& the &lat bar against the rail on the opposite side o& the 'ise &ro" where he)s standing. 3he other person+ standing opposite the the &irst person+ s"a!s s"a!s the &lat bar+ starting at one end and woring to the other end.  @ote that in this pi!ture+ it)s ust being held in pla!e with one hand &or display. display. 3he bar holder needs to be dire!tly behind the 'ise+ holding both pipe handles to align it properly as the ha""er "an "aes ea!h stroe.

3his needs to be done with the bending &iture !la"ped in the 'ise+ not only to eep the sides o& the re!ei'er tight against the die &or a good go od uni&or" bend+ but to eep the die &ro" slipping down in the outside &or". As the upper rails start start to bend o'er+ the person person holding the woring bar needs to eep it at the sa"e angle as the rail until the bar is 'erti!al ("eaning that the rails are laying &lush on top o& the die#. 3he ha""er operator ust wors up and down the woring bar. e used a 5$lb 5$lb sledge ha""er and % &ound it generally too "e 5 stries along the length o& the bar &or ea!h BpassB. A&ter % "ade a pass+ the angle would be !hanged and %)d %)d "ae another pass. %t usually too us  passes to get the rails laying down &lat on top o& the die. 3hat)s only 15 ha""er stries on the woring bar &or ea!h rail. hen the rail was laying &lush on top+ we)d "ae "ae one "ore pass B&or good "easureB+ "easureB+ "aing "ore lie  stries stries (!loser together# to to ensure uni&or"ity. uni&or"ity. 3he result was superb.

3he tri! is ust to tae your ti"e+ "ae good solid ha""er stries with a hea'y sledge ha""er+ and to eep the woring bar at the the !orre!t angle. And depending on how "any re!ei'ers you)re you)re "aing+  be prepared to ha'e to repair your woring bar. -urs was beat all to hell on the top. % was ha'ing so "u!h &un+ % was 'ery eager on the sledge ha""er. :$# %n retrospe!t+ the woring bar would ha'e been better i& the handles were at about a 120 degree angle &ro" the &lat bar instead o& 90 degrees as ours were. hen striing near the end o& the bar+ % had to  be !are&ul not to hit "y asso!iate)s hands as he was holding the handles. So+ i& you want to "ae a woring bar &or the upper rails+ eep sa&ety in "ind. and angle the handles out away &ro" the "iddle where the ha""er will be striing. %t)s also a good idea to ha'e a step stool or so"e way o& getting higher abo'e your 'ise as the angle !hanges on the upper rails. ou don)t want to to be swinging a sledge ha""er that high. et abo'e it so you ust ha'e to li&t it and "ostly let gra'ity do the ob when it)s at that that angle. %t)ll "ae the ob a lot easier and you)ll get "ore uni&or"+ solid blows. And this is one o& the steps where &atigue will get you. % busted "y nu!le a &ew ti"es when % was tired and "ade a glan!ing blow o&& the woring  bar. Sa&ety &irst+ ya now.

Step %: Remove the die from the outside form

3his is &airly straight&orward. straight&orward. -n!e the upper rails are bent and pass your 8uality !ontrol inspe!tion+ un!la"p the &iture &ro" the 'ise. -pen the aws o& the 'ise a bit wider+ turn the &iture upside down and set it on top o& the aws. 3ae a pie!e o& bar sto! and at least a 5$lb sledge sledge ha""er and ha""er

the die ba! out. %t should start !o"ing out o& the outside &or" and go between the open aws o& the the 'ise. ,ay a pad o& so"e sort in there so i& it it &alls out it won)t get dinged up. =on)t put your hand under there to !at!h it as your buddy ha""ers it outE As "e about how "y &inger got s"ushed when the 5$lb sledge ha""er and the weight o& the die landed on it. And eep in "ind+ when you)re doing this+ you)re ha""ering on the underside o& the botto" plate o& the die. %& your bolts that !in!h up the &lat inside the die are protruding &ro" the botto" o& this this  botto" plate (as ours were by ust about 1/B#+ you)ll want to be !are&ul not to hit the" with with your bar sto! when ha""ering out the die &ro" the outside &or".

hen the inside die !o"es out+ you will noti!e that the sides tend to spring ba! ust a tad away &ro" the &or". 3his is nor"al+ and to be epe!ted. %t will be pulled ba! together at the trunnion lo!ations when you  build this into an A> ri&le+ with the ri'ets or s!rews (or whate'er you)re using#+ as well as at the !enter support. So don)t worry about it.

ou)ll also see in this pi!ture+ that there is grease where the top rails rails were &olded o'er. 3his "aes a handy gauge o& your upper rail bending pro!edure. %& you properly greased the area+ it will s8uee7e the grease out when the upper rails are tight on the top o& the die.

Step &: Remove the receiver from the die

So now the die is out o& the outside &or". &or". ou !an re"o'e the bolts to un!la"p the re!ei'er &ro" the the die+ whi!h should release the botto" botto" plate. ou)ll also noti!e that+ oddly enough+ your your &lat a!tually loos a lot lie an A> re!ei'er.

 @ow+ the botto" plate is released and you si"ply need to re"o'e the die &ro" inside the re!ei'er. 3he ni!e thing about the bending &iture we used was that the top o& the die had a raised strip down the "iddle that was parallel with the botto". So this "ade a handy pla!e to !la"p in a 'ise as shown  below+ and tae another pie!e o& bar sto! and tap the re!ei'er o&& the &or" slowly+ "aing sure not to de&or" any "etal. %& you greased it properly+ it should !o"e o&& with little little e&&ort and only light taps. e tapped on the rear end o& the re!ei'er where it)s a ni!e wide bearing sur&a!e+ to "ini"i7e any proble"s.

Summar' and miscellaneous comments

3hat)s itE ou)re doneE ou should ha'e a bent re!ei'er now. ipe o&& all the grease and get to  building your A>. As % said at the beginning+ this pro!ess should tae 15$20 "inutes on!e you get the hang o& it. 3he really hard wor is already done &or you i& you)re you)re using a 3ap!o &lat that already already has all the holes in it. % !hose to use &lats that didn)t ha'e trunnion holes in the" already be!ause o& the "ethod %)" going to use &or "ounting "y trunnions will be di&&erent. 4ut the pre!ision part o& &abri!ating a re!ei'er is all in the &lats and the bending ig. %t)s al"ost idiot$proo& (noti!e (noti!e % said Bal"ost :$# #. 4e&ore % wrap this up+ % do want to point out a &ew other things. A lot o& builders that ha'e bent their own &lats ha'e noti!ed stret!hing/distortion stret!hing/distortion around the "ag well well opening. 3his is presu"ably  be!ause there isn)t really any "etal on the botto" o& the re!ei'er in that area+ and as it bends in the &iture+ it pulls up on the sides. % did not noti!e any distortion distortion o& the "ag opening whatsoe'er. %t si"ply wasn)t an issue &or us. 3he design o& the &or" (with two bolts through the "ag well whi!h put a good bind on the "etal on either side o& the opening# plus !opious a"ounts o& grease in the &iture ept it &ro" e'er being an issue. Another !o""on issue is elongation o& the trigger pin ($ais# hole. And we did see that on our re!ei'ers. 4e!ause that hole is so !lose to the !orner+ the botto" o& the  is on the bend+ and there isn)t any "etal abo'e it be!ause o& the hole+ so it doesn)t bend lie the rest o& the re!ei'er. 3his leads to the trigger pin hole ha'ing a BdipB at the botto". ou !an see it in the &irst pi!ture o& Step < o& "y tutorial+ abo'e. 3his is easily &ied by woring the "etal gently with a ha""er around the botto" botto" !orner be&ore tapping it o&& o& the die. e !hose not to worry about it be!ause it)s an o'ersi7ed o'ersi7ed hole anyway+ so it)s inherently stronger stronger than the s"aller s"aller hole on the other side already. already. lus it)ll be heat treated. And the pin isn)t going to be loose in the hole or anything+ as the distortion is relati'ely relati'ely "inor there. %t)s really "ostly "ostly ust a !os"eti! issue issue as &ar as % !an tell. %& it bothers you+ round it o'er with a ha""er and wor it it ba! to the original shape shape o& the hole. @o biggie. 3ools. 3o bend a &lat+ &lat+ you)ll need so"e so"e basi! tools or at least a!!ess to the". the". -b'iously+ you)ll need a shop press. 3he 20$ton "odel &ro" &ro" ;arbor Freight wored lie a !ha"p. !ha"p. A 12$ton should do it too+ % hear. % e'en thin it !ould be done by hand+ with a de'i!e %)'e designed. %t will be undergoing testing possibly in the the near &uture+ but "ore on that later. For now+ the sa&e bet is using a press. %t "aes short wor wor o& it. ou)ll also need a good solid "ounted 6B ben!h 'ise. % !ouldn)t see doing it with a s"aller one. All the ha""ering and !o"pressing !o"pressing that)s needed &or this this using the 'ise+ a s"aller one would be !hallenged to get the ob done. G'erybody needs a 6B 'ise anyway+ so ust ust buy one. ;arbor Freight is is your &riend. &riend. 3hen there is the woring bar+ i& you !an get one "ade or "ae "ae one yoursel&. %t sa'es a lot o& ti"e and trouble trouble %;-. ;a""er$wise+ we did pretty "u!h "u!h e'erything with a 5$lb sledge (bending the upper rails and re"o'ing the die &ro" the outside &or"# and a $  pounder &or lighter wor lie no!ing o&& the re!ei'er &ro" the die. A plain$ane so!et set &or the  bolts on the die. A !an o& grease and ,G@3 o& shop rags+ as well as degreaser. 4ut what !a"e in the "ost handy was "is!ellaneous bar sto!. e used it &or shi""ing the ra" on the press when repositioning to the ends o& the die+ we used it &or ha""ering the die out o& the &or"+ we used it &or ha""ering the re!ei'er o&& the die+ and we used it &or shi"s in !ases where we had pushed the die too &ar into the &or" and needed need ed to push it ba! up and botto" it out against the botto" plates o& the &or". % highly re!o""end ha'ing so"e pie!es o& bar sto! laying laying around+ o& 'arious si7es and shapes.

So that should pretty "u!h !o'er "y eperien!e with  bending &lats and detail how to use this parti!ular bending &iture. i'e it a whirl and enoy yoursel&.