AK47 Forums > AK47 Kit-Build Discussion
New Technique for AK Builds
Toad:
A similar link poped up on Gunco...I'll see if I can find it...again. 'Cept this guy used these to fix a screw build that went wrong.
LESchwartz:
Guys,
I would throttle back the temptation to get too excited over this technique until we get more data. Many builders already worried about stripped and deformed threads on screw builds -- these fasteners would seem to have these same concerns, only worse. I would really worry that with time the vibration would wear on the "threads" and cause these to loose their grip.
If someone has a "machinist's manual" they should be able to get us the specs (shear strength should be similar to rivets). But only time will tell if the these will stand really stand up to the punishment . . . On an AK the front trunnion rivets really don't take a lot of punishment, since those forces are contained when the bolt locks into the trunnion. The rear trunnion rivets are the ones that really take the abuse. I wonder if we could do "accelerated wear testing" by using these fasteners in the rear trunnion and see how they hold up . . . ?
Larry
1952Sniper:
I keep hearing people say that the rear trunnions take more abuse than the front trunnions. But I'm not sure I believe that. If the recoil force of the rifle is translated to the receiver through the rear trunnion, then it's translated to the front end of the rifle through the front trunnion too. The receiver is the connector. Both the front trunnion and rear trunnion translate the impact. Granted, there are generally less connectors on the rear trunnion. So each screw/rivet on the rear trunnion has to do 50% more work. I can see that.
Is that what you mean when you say the rear trunnion takes more abuse?
doneking:
Believe me, I'm concerned about the holding and strength of these U drive screws also.
I've requested some technical data on them from the supplier/manufacturer. If I get any response, I'll post them here.
After putting some thought to this and speaking with a machinist that I trust a lot and is a good friend, He gave me this explanation on how these work when installed properly.
This is an original basic picture of a U drive screw.
This is depiction of what essentially happens when these are installed.
They act basically like a rivet to some means by using the little button tip that is on them. It pushes with force on the material as it bottoms out. These could only be effectively used where there is backstop if you will, that gives it the ability to 'squish' itself.
He went on to explain that they can be even stronger than a rivet because it seizes itself with the screwing action. Kind of like when galling occurs when a bearing goes bad.
After this thinking I feel even more secure in this technique. I am open to opposing opinions. I can still change my mind if this is a bad idea.
DK
LESchwartz:
--- Quote from: 1952Sniper ---Is that what you mean when you say the rear trunnion takes more abuse?
--- End quote ---
When I say the rear trunnion takes more abuse, I mean that it also is the rear stop for the bolt.
Larry
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