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View Full Version : Compilation of Receiver Forming Steps



bladeworks123
08-20-2012, 10:40 PM
I've been meaning to post this for some time, just because I think it's interesting and gives some insight into how an Hk G3 receiver is manufactured. Another post reminded me to do it, so here they are....

These pictures were taken at the Oberndorf Plant/Museum, courtesy of a Sam Pikula, sent to me by a friend of mine who is one of the best Hk armorers I know.

Step 1
33977

Step2
33978

Step3
33979

Step 4
33980

Step 5
33981

Step 6
33982

Step 7
33983

Perro Del Diablo
08-21-2012, 12:42 AM
got the pictures of the different dies that form these? i think i still do, will look if you dont

bladeworks123
08-21-2012, 12:45 AM
I only have two die pictures and they don't really show much, can't really tell even what stage they are in. That would be a nice add if you can find them.

Perro Del Diablo
08-21-2012, 01:12 AM
I only have two die pictures and they don't really show much, can't really tell even what stage they are in. That would be a nice add if you can find them.

Here are some of them.
Todd took better pictures of each one of them at one time, but im trying to find where i have them stored. I thought i had it on the same CD as the HK manuals, but apparently not

Perro Del Diablo
08-21-2012, 01:20 AM
These are the dies that make up the miniature CETME

Perro Del Diablo
08-21-2012, 01:39 AM
one more post, and im done with the topic until i find the other pictures im missing


I was trying to explain in the other thread that as long as the trunnion is butted up against the rails, then its in the right spot in relation to the magwell. I tried to respectfully disagree and go against the popular opinion that the rails need fitted to each individual gun, and i claimed that no fitting required because the rails are stamped in the same spot in relation to the magwell every single time a flat is bent - study these 2 images
http://www.militaryfirearm.com/Forum/attachment.php?attachmentid=33993&stc=1&d=1345526018http://www.militaryfirearm.com/Forum/attachment.php?attachmentid=33994&stc=1&d=1345526018


those are the male and female dies that stamp out both the rails, and form the magwell all at one time. They correspond to step 4 in the flat pictures

http://www.militaryfirearm.com/Forum/attachment.php?attachmentid=33980&d=1345516548


The rails are formed at the exact same time that the magwell is formed on the same die

that means that the rails are in the same spot compared to the magwell on every single receiver, and as long as the trunnion is butted up against the rails, then its in the right spot for the magwell to latch the mag on the trunnions lips - the rails have to be in the same spot compared to the magwell because they are formed at the same time with the same die.



now, let me go find the other photos

blkadder
08-21-2012, 09:11 AM
I really like all those pictures. It gives a good visual on how they form the flats, and the amount of detail possible from a pressing. On a side note, how do I get one of those mini CETME rifles? :084:

Thanks for posting these pictures guys.

Ron

Blackwing
08-25-2012, 08:20 PM
I would be VERY interested to see detailed pictures of each stage. Who's dies are these? Were these the ORF dies now with GW?

jdowney
08-25-2012, 08:25 PM
That mini-cetme is extremely cool! :thumbup:

Milsurp
08-25-2012, 08:52 PM
That mini-cetme is extremely cool! :thumbup:

Yes indeed it is. Where would one find something like that. I believe I need one.

bladeworks123
08-25-2012, 09:52 PM
.....The rails are formed at the exact same time that the magwell is formed on the same die

that means that the rails are in the same spot compared to the magwell on every single receiver, and as long as the trunnion is butted up against the rails, then its in the right spot for the magwell to latch the mag on the trunnions lips - the rails have to be in the same spot compared to the magwell because they are formed at the same time with the same die.



now, let me go find the other photos

I disagree, the length and position of the front end of the rails is not done at the same time the mag well is formed,,, I contend that since the rail cuts are made on the first die together with the locating holes at the rear, that that first step determines the location of the rails forward end. The location of those cuts predetermines the length and position of the front of the rail. As those dies wear or if the blank is off by a bit when the first cuts are made it can result in the rails being slightly different front to back or in length from one side to the other when the mag well is formed three steps later. I always check the distance to the front of the rails from the back of the magwell to make sure that they are 82mm forward on both sides. I have to trim one side or the other, or both, on the old ORF flats, often as much as 2mm or so, and they differ in length sometimes by as much as 1mm. I realize that their dies were badly worn.

Some of the ORF flats were also stamped deeper on one side than the other, resulting in the trunnion housing ending up off center when the receiver is rolled together. I think Century must have had receivers formed from those dies as well, or had the same problem, because I've found a number of CAI Cetmes that have the trunnion setting off to one side and the rail on the opposite side is not flush to the trunnion. I used to think that they just didn't press the receiver in tight enough until I discovered the off center trunnion problem. I came up with a jig that lets me press and shift the trunnion from one side to the other to fix that. I have had to trim a couple of JLD receivers. Tim's flats from Gewehr Works are fairly close, within .5 mm. I learned that measuring step from an Hk armorer who also checked the rail lengths on replacement Hk receivers, as well as the distance from the rear of the magwell to the front of the magwell at the leading edge (92.5mm) That distance can be changed a bit by pressing the flares down on the front corners of the magwell after it is welded together.

I've only welded up three or four of them, and have 1 on the bench to do now of the CAI cast receivers, which also have to be trimmed inside to get the trunnion back far enough, but that is more understandable on a casting.

Perro Del Diablo
08-26-2012, 11:51 AM
I disagree, the length and position of the front end of the rails is not done at the same time the mag well is formed,,, I contend that since the rail cuts are made on the first die together with the locating holes at the rear, that that first step determines the location of the rails forward end. The location of those cuts predetermines the length and position of the front of the rail. As those dies wear or if the blank is off by a bit when the first cuts are made it can result in the rails being slightly different front to back or in length from one side to the other when the mag well is formed three steps later. .


almost impossible due to the way the flat is set into the jig in the punch press

the flat is indexed to the punch die where the rail holes are formed and then the rails are pressed at exactly the same time as the magwell in the forming die.


Wear of course is a big problem, and CAIs dies ARE worn, but funny that some receivers allow the mags to seat but others dont? If some receivers fit, but some dont, and the flats are indexed in the dies, then how is that possible? The flats are indexed to the punch dies - so where do the inconsistencies come from? Foldup and weldup where things shrink and warp

holescreek
08-26-2012, 12:58 PM
All production manufacturing requires tolerance allowances to function at peak efficiency. Punch and die clearances are sized to allow the locating pins in the next operation fit. As tooling wears some items get sloppy, others get too tight. Guide pin bushings wear and the dies don't close squarely anymore. Operator intervention plays a role too as the stamping is moved from one op to the next. It can be as simple as placing the flat against the locators and then tugging on a corner to get it aligned. On a single stage die where everything is done in one hit it's not an issue. On multistage die setups it is. Add into the equation die sets that are way beyond their expiration dates, where details are worn to rounded edges and cutting edges are galled up or broken and you are lucky if a flat even "looks" right.

Material properties of the sheet metal used also come into play. You will most often see the good steel certified (although that means less today than it did before the computer age) but the good stuff costs more. Where is the profit in using the good stuff? Die set and material lubrication can be added into the mix.

In a perfect world the production dies are set up by skilled individuals and the top and bottom dies are parallel and shimmed to provide proper material clearance for the sheet being used that day. The die sets are clean with no residual material or dirt. All the cutting edges are sharp and the punches are aligned with the dies. They are properly lubed to allow metal to stretch and bend without galling. The material is of the proper thickness and is consistent through out without hard or soft spots.

Look a the corners of the relief cut in front of the rails on any new flat and most often you will see cracks radiating from the corners. You will see the material around punched areas "puckered up" from improper die clearance or just plain wear. Does it hurt anything? Not for our purposes. Are the parts in tolerance? Maybe, maybe not. Are they useable? With a little work and care by the builder. Are they consistent? Everything made in the same day, same materials, same conditions will probably be as good or bad as the parts made before and after it.

I have never bent a gewher works produced flat (I still have too many ORF flats sitting on the shelf) so have zero experience with them. I know they fixed some of the most glaring issues (squared rails) but doubt that they invested the money to fix everything for a dying market. We're just lucky to get something "close enough" to work with. If Century has a set of dies do you really think they care about everything I mentioned above?

Blackwing
10-02-2012, 08:35 PM
Perro, did you ever find the die pictures for this series?

Perro Del Diablo
10-03-2012, 08:47 PM
sadly no i havent found the other pictures. I had a complete set of them saved somewhere but im unsure where they are. I have a bunch of backup CDs and DVDs and they should be on there somewhere, but i havent had time to find them, i have been super busy sorry.

Blackwing
10-10-2012, 09:48 PM
I can wait. But would be VERY interested in seeing them. Were they complete and detailed? I would be willing to pay a "finding them fee" if they were very detailed.

Blackwing
10-17-2012, 01:56 PM
Just a TTT for this thread in hope of pictures.

Blackwing
10-31-2012, 09:10 PM
TTT for da pics

Perro Del Diablo
11-01-2012, 12:19 AM
TTT for da pics
I dont believe i have the other pictures anymore.
Todd took pictures of all of them for me - even the ones for the magazines and the grip frame, but im not sure what happened to the pictures, sorry.

Ask MWDG3, I think i sent him a copy of the pictures many many years ago, and he may still have them

Blackwing
11-13-2012, 10:19 PM
No luck from MWDG3....I guess they are gone forever. What a loss..