Long Rivet From Hell...VICTORY!!! Post #32

[oogabooga]

So I've been demilling a Yugo underfolder AK rear trunnion with less than stellar results. There is some dumbassery on my part, so you don't need to point it out . All of the rivets for the front trunnion came out fine. All of the short rivets in the rear UF trunnion came out fine. But the single long rivet on the UF rear trunnion has been kicking my *** (and fingers) for the past two days.

After angle grinding the rivet heads off and removing the receiver stubs, I drilled 1/8" holes about 1/3 of the way in on both sides of the beheaded long rivet. I "folded" in the edges of the rivet with a punch so the rivet didn't get smashed and hang up on the swell neck cutouts. I then proceeded to pound at the rivet with a punch and hammer from the right side of the trunnion (right side if you were looking down the sights). I got down maybe 1/4" and the rivet material wouldn't budge no matter how hard i swung. And so begins the personal fail...

I decide to flip the trunnion over and hammer from the left side of the trunnion. I do so, and again, the rivet material stops in its tracks. I then think to myself "You've hit your fingers plenty of times already swinging the hammer, yet your fingers aren't even bruised yet. Man-up and swing harder." I do start throwing blows at the punch harder, until the punch snaps...with the break point inside the trunnion. I do a mental facepalm right about here and think of my options. I could either stop here and consult the internet to see what to do, or try to figure this out myself to avoid the shameful embarrassment of how you couldn't pound out a rivet. Anyway. The broken punch is stuck in there pretty damn good. I try drilling it out with the drill press but that broken piece is hard as a rock. I then think "Well, if I use a different punch and continue hammering from the left side, I'm basically just pushing the broken punch with another punch. That should be fine."

So I go to my drill press and use a 5/32" bit and drill out more material from the right side of the trunnion since material has since been compacted from the very first attempt at hammering the rivet out. The hammering proceeds from the left side of the trunnion again, trying to push the broken piece through the trunnion hole. It doesn't move...

Now I think about here, I'm just blinded with frustration and don't think this next step through. So try not to laugh too hard. I take my punch...and stick it in from the right side of the trunnion and try pounding it the opposite direction. Yea. Broken punch. Inside the right side of the trunnion. I again try drilling it out, but of course the damn punch is too hard for me to drill out. I use a THIRD punch to try to drive them all out from the right side, smashing my fingers from swinging like a madman with no coordination left. But I persist. Eventually, I remove my working punch and realize the tip has been mushroomed. I gain some of my composure back and realize that the two broken punches probably did meet in the middle. But mushroomed out INSIDE the trunnion, causing an unbelievably tight fit that would make the barrel and front trunnion fit seem like throwing a hot dog down a hallway.

I tried using heat from a soldering iron, but no dice.

So that's where I am. Discolored fingernail and blistered hand. Broken pride and defeated spirit. I could always buy another rear UF trunnion, but doggonit, I want to use this one if only to say my last 2 days weren't wasted. Sorry for the long read. Any suggestions?

Update Post #32

[nicoroshi]

Been close to that myself when helping a couple of friend drive out the rear rivets.

The punch is hard but also brittle when taken at a angle (hence the broken pieces in the rivet hole). The drill bit will not be able to drill through the punch.

Bottom line. The punch needs to come out.
My recommendation is to go at the punch with a pointed punch to crack it into pieces that can be removed. Once the pieces are removed, and you're back to a rivet drill at least halfway through then keep stepping up your bit size until one side is hitting the interior of the trunnion (you'll know by the sound). That doughnut rivet is now a 'c' shape. Now drive the rest out with the largest punch you can get into the hole without hitting the trunnion.
You'll get it brother. Just have to be more stubborn than the rivet.
Oh, Also when you've had enough for the night let that trunnion soak in WD-40 until the next day when you work on it again.
FYI: Holding the punch with a pair of vice grips saves the fingers.

[4thSBCT]

very good story.....sounds like you started to get in a hurry. I've been guilty of that many times...one thing I learned very early on is go slow and if you screw up, its time to take a break and consult a few calgunners....

If this were my trunnion at this point. I would try taking the smallest drill bit you have and start drilling out the punches. I've found that using the smallest bit is able to penetrate better. Drill until each side meets in the middle then step up to the next size .....then the next size....then the next size...It will take a long time but should work in the end. If the bits don't work try getting a countersink bit to start it off and then use the regular bits in the same way. The long rivets punch out much easier when there is a complete section missing in the middle which means before you punch it out you should be able to peer through the hole and see out the other side. This will relieve the pressure on the rivet making it much easier to drive out. If you dont drill all the way through and try to punch it out. your just caving the walls in and packing it in harder. Use lots of cutting oil and go slow. good luck.

[oldyeller]

Carbide drill bit? Also when pounding, be sure to have a very SOLID base to pound against. I use a piece of 3/4" plate with a hole that the rivet can go through on a concrete slab and a 3lb sledge.

[SJgunguy24]

Been there before, I drill with 1/8" then 5/32" from both sides and never let a punch anywhere near the long rivets.

What I do in your situation is use an air hammer, I have a hammer bit that I turned down to fit inside the 4.5mm hole. Hope this helps.

[oogabooga]

Been close to that myself when helping a couple of friend drive out the rear rivets.

The punch is hard but also brittle when taken at a angle (hence the broken pieces in the rivet hole). The drill bit will not be able to drill through the punch.

Bottom line. The punch needs to come out.
My recommendation is to go at the punch with a pointed punch to crack it into pieces that can be removed. Once the pieces are removed, and you're back to a rivet drill at least halfway through then keep stepping up your bit size until one side is hitting the interior of the trunnion (you'll know by the sound). That doughnut rivet is now a 'c' shape. Now drive the rest out with the largest punch you can get into the hole without hitting the trunnion.
You'll get it brother. Just have to be more stubborn than the rivet.
Oh, Also when you've had enough for the night let that trunnion soak in WD-40 until the next day when you work on it again.
FYI: Holding the punch with a pair of vice grips saves the fingers.

The funny thing...I had a pair of vice grips right next to me from prying the receiver stubs just prior to this fiasco -.-
But great info! Since I have so many broken punches, I might just try grinding down one of them to create that pointed punch to try and crack the punch-pieces. I did not know that and wouldn't have even thought of it. It's too late to go grab a can of WD-40 (I'm all out), but I'll get on that if the problem persists.

Also, I like the idea of the C-shaped rivet. I'd imagine that would come out nice and easy.

very good story.....sounds like you started to get in a hurry. I've been guilty of that many times...one thing I learned very early on is go slow and if you screw up, its time to take a break and consult a few calgunners....

If this were my trunnion at this point. I would try taking the smallest drill bit you have and start drilling out the punches. I've found that using the smallest bit is able to penetrate better. Drill until each side meets in the middle then step up to the next size .....then the next size....then the next size...It will take a long time but should work in the end. If the bits don't work try getting a countersink bit to start it off and then use the regular bits in the same way. The long rivets punch out much easier when there is a complete section missing in the middle which means before you punch it out you should be able to peer through the hole and see out the other side. This will relieve the pressure on the rivet making it much easier to drive out. If you dont drill all the way through and try to punch it out. your just caving the walls in and packing it in harder. Use lots of cutting oil and go slow. good luck.

Yea, I was kind of in a rush. I wanted to get this demill done this weekend. Looks like that ain't happening
I do recall removing both the long rivets from a previous RomyG build. They were a pain in the ***, but not nearly as bad as this one. I think that was my main problem. In the Romy build, I did drill all the way through, but I ended up slightly egging out the holes be trying to drill it out all the way from one side. I didn't want to risk egging again, but I shouldn't have been so conservative with the drilling this time. I think I've conceded that drilling out the broken punches isn't going to work. The bits keep walking when I get close to them. But I do see the error of my ways. Drill all the way next time! (1/2 and 1/2 on both sides, of course).

Carbide drill bit? Also when pounding, be sure to have a very SOLID base to pound against. I use a piece of 3/4" plate with a hole that the rivet can go through on a concrete slab and a 3lb sledge.

I was using a scrap piece of wood. I know that the wood will crack and get dented up, but I wasn't too concerned about that. I felt if the surface I was pounding on was too hard (ie. concrete floor), the bits seemed to bend and break a lot easier since the shock is being sent HARD back up the punch. The wood would also give way so the rivet would have somewhere to go.

Been there before, I drill with 1/8" then 5/32" from both sides and never let a punch anywhere near the long rivets.

What I do in your situation is use an air hammer, I have a hammer bit that I turned down to fit inside the 4.5mm hole. Hope this helps.

Hmm. An air hammer would be nice right now. I tried using the gear puller I used to remove the barrel, and tried to make it so it worked as a press to push out the rivet+punch combo. But that was another failure. I would like to use a 5/32" drill bit to go all the way through, But I don't trust myself or my cheapo drill press to stay straight and true.

Thanks, guys, for all the info. Keep it coming!

[SJgunguy24]

, But I don't trust myself or my cheapo drill press to stay straight and true

Damn dude really? I use a cordless or an air drill. I almost never use a press when demilling.

[oogabooga]

, But I don't trust myself or my cheapo drill press to stay straight and true

Damn dude really? I use a cordless or an air drill. I almost never use a press when demilling.

I just don't wanna make the trunnion hole any bigger than it has to be in the event the bit walks or bends. The hole is barely 5/32" as it is, and getting a drill bit stuck in there because it's too tight would be just as bad as the situation I'm currently in. But if you can get it centered with a cordless drill, more power to you.

[nicoroshi]

Cordless is fine. You'll know by the sound if you start drilling into the trunnion. The metal of the trunnion is much harder than that of the rivet, and chatters something terrible when a drill bit hits it.

[SJgunguy24]

Do you have access to a roto hammer? You could flip to chipping mode and give that a try.

[oogabooga]

Cordless is fine. You'll know by the sound if you start drilling into the trunnion. The metal of the trunnion is much harder than that of the rivet, and chatters something terrible when a drill bit hits it.

The chatter is a very disconcerting sound. And sometimes the hole is too tight and will stop the drill's motor all together and make that whining sound. Then if your piece isn't secured with a vice or something similar, your work starts spinning with the bit. I imagine that can't be good for...well...anything lol. I have drilled into the trunnion a bit, too. And didn't want that happening again. I'm sure I could've used a crank drill like the ones back in woodshop for elementary school kids to drill out the rivet. It's these broken punches, now, that I'm worried about. But I'll keep all these ideas in mind if I ever demill again

[oogabooga]

Do you have access to a roto hammer? You could flip to chipping mode and give that a try.

Unfortunately, I don't. But if what nicoroshi said about the broken pieces of the punches being brittle is true, that would work wonders! I'll try shaping a pointed punch when daylight comes (and I have time) and see if that gets me anywhere with just my bare hands. I may have to see if anyone I know has a roto hammer if that doesn't pan out. Thanks for the quick responses!

[oogabooga]

I know this triple post looks bad, but it wasn't intentional.

Well, I tried sharpening a couple of the old punches to a point to try to break the punch-pieces, but the point kept flattening out. The metal was too soft (or of equal hardness. Imagine that ). I also tried a sharp nail, but again, the metal was too soft. I went to OSH to pick up some other supplies, and picked up a cobalt and tungsten carbide tipped 5/32" drill bit to see if that was hard enough to drill out the punch-pieces. But of course it wasn't.

So I'm going to need something sharp, and of harder metal than the punch tips...

[SJgunguy24]

I know this triple post looks bad, but it wasn't intentional.

Well, I tried sharpening a couple of the old punches to a point to try to break the punch-pieces, but the point kept flattening out. The metal was too soft (or of equal hardness. Imagine that ). I also tried a sharp nail, but again, the metal was too soft. I went to OSH to pick up some other supplies, and picked up a cobalt and tungsten carbide tipped 5/32" drill bit to see if that was hard enough to drill out the punch-pieces. But of course it wasn't.

So I'm going to need something sharp, and of harder metal than the punch tips...

Location?

[oogabooga]

Location?

Right now I'm in the Norcal south bay area.