That's the 1st time I've heard that you can't rivet after tapping your trunnion. I was wondering why you can't just go ahead and use slightly bigger diameter rivets after tapping? BTW, I'm not argueing, just asking, as I've come to hold your opinions in high regard !hcpookie said:- One-way decision... tapping the trunions alter them beyond usage for anything other than a screw build.
[font=verdana, arial, helvetica]I finished mounting the trunnions on my KVar Bulgy AK-74 kit last weekend. It'd been sitting for 6 months waiting for "the right tools" - which I can't afford (just started a business AND bought a house), so I finally just decided to make do with the tools I have. I figured that I would list some of the the steps that I use in case someone else out there doesn't have a press and I DYING to get their AK done.
Plus, I'm not saying that this is the correct way (or the safe way) it's just the way that worked for me.
* First, I got the old sheetmetal receiver stub off of the front trunnion. I tried my Dremel tool with a but after an hour of sweat I borrowed my neighbors grinder . . . five minutes later the receiver stub was gone and I realized I had one more tool that I HAD to buy
* I then tried to get the rivet remains out of the holes in the trunnion. For the life of me, I couldn't get even one all of the way out. I realized that I was going to need to press out the barrel somehow. Considering my distinct lack of a press, I was left with a hammer and a variety of beating implements. First off was the barrel pin . . . after breaking a punch and nearly fracturing my wrist with a 16 oz framing hammer, I broke down and made a quick trip to Home Depot and grabbed a new punch and a 4 lb mini sledge. That bastard was coming out one way or another. It's AMAZING how hard I had to hit it to move it. Once it started and broke the shear plane, it came out with only a minimum of swearing. Which left me with the barrel in the trunnion . . .
. . . I just dropped 3 pennies against the chamber face, hooked the back of the trunnion over a secure flat metal surface, placed a 7/16 deep well socket against the pennies, and proceeded to lovingly and carefully beat the living shit out of the thing. Some advice if you do this - have plenty of pennies, they don't last long AND wear thick leather gloves (don't ask me how I know this) AND use a Craftsman socket so that you can exchange it once you mash it into scrap. I was careful to watch the barrel face and trunnion for damage and eventually the barrel popped free. I then proceeded to dance around the shop waving both parts above my head, shouting a victory chant much to the concern of my poor long suffering wife (I have WAY too many hobbies). I then drilled the rivets and punched them out.
* I was using a hardened OOW receiver, so I needed to lay out the drilling pattern for the screws. This part really made me sweat because I knew that once I drilled a hole it would be permanant - I don't have access to a welder AND it would screw up my heat treating. So, I measured 453,276,920,768 times and drilled once. I popped everything into my el-cheapo press, clamped the receiver down and drilled with the trunnions visegripped into place in the receiver. After using a small bit to check alignment I ran the bit all the way through the trunnions to get both sides in one shot. It worked perfectly.
BTW, Chris at AK-USA heat-treated my receiver. It really didn't make any differance in the build. I used cheap HSS bits and it cut the steel like butter as long as I used cutting fluid.
* After drilling it was time to tap. Let me say ahead of time that I have never tapped a hole in my life. I'm a network engineer by day which means that I'm pretty good at designing a 2 million dollar EMC SAN Fibrechannel storage solution, but pretty worthless in the shop with hand tools. So this part scared the bejeezus out of me. I kept hearing stories about folks breaking taps in the freakin' trunnion holes even when they used really nice quality taps. I looked on my shop table at the $3.88 10-32 HSS tap that I got at Home Depot and decided that I was not going to be outwitted by an inanimate object. If you've never tapped before, the following ideas may be helpful.
- Get and use a good quality tapping/cutting oil. Use LOTS of it. In my (albeit limited)experience, there is no such thing as TOO much
oil. Oil has the added benefit of removing heat.
- Go slow. If you're in a hurry it will not turn out well. I made myself take a five minute break between holes.
- Heat is your enemy. Tapping creates an immense amount of friction, which creates heat. Lots of it. Enough that you may need gloves to hold your work. As your work heats, the tap expands. This will make your holes oversize and increase your risk of tap breakage. Go slow, reverse often and give the tap time to cool and break chips.
- IMNSHO, don't use a press mounted tapping rig. I rigged one up and it seemed to be much more difficult to align because there was no "give" in the system. I just held the parts in my hands and used gloves.
I'm proud to report that I was able to complete both trunnions with one tap.
* Then, after checking the trunnion fit in the receiver(pretty much perfect) I decided to remount the barrel. Once again, I had no press AND brute force would not work this time. Beating a barrel OUT is much simpler than beating one IN. So, following the advice of those before me (you guys) I tossed my barrel out into the snow (it was 15 F) and grabbed my propane torch and carefully heating the trunnion up. I ran outside, got the barrel and tried to insert it into the trunnion. It went in 1/4in and stopped cold. Out came the pennies and the much-abused 7/16 socket and I removed it again. I then proceeded to spend an hour beating my head against the wall trying to rig up a car jack as a barrel press (admit it . . . you've tried or though of this at least once). I finally really looked at the barrel journal and noticed that the thick black paint on the chamber end was what was blocking the barrel from being inserted. Out came the 220 grit and away the paint went. I threw (well, placed gently) the barrel back out into cold and heated the trunnion. I grabbed my gloves, got the barrel and tried to slide the barrel into the trunnion . . . WOOHOO! Perfect fit, right on the barrel pin line with NO EFFORT AT ALL. You could have knocked me over with a feather. Maniacal chanting ensued . . .
* Finally, i had to replace the [email protected]$%#[email protected] barrel pin. After my experience with heat/cold though I was much better prepared to do this. Cold pin + hot trunnion + 4 lb sledge + two smashed fingers = inserted pin.
* Create plate for trigger guard, contersink receiver into trunnion, cut bolts, toctite, blah, blah, blah. Everything else was easy.
Well that's my adventure SANS press. My advice - get a press and avoid the headache. I'm building a GT PMKMS kit next and I'm waiting for proper funds for the right tools. But, if you're as impatient as I am, good results can be achieved.[/font]
Yeah no problem - that's what we're here for! I should have been more clear...Grendeljaeger said:That's the 1st time I've heard that you can't rivet after tapping your trunnion. I was wondering why you can't just go ahead and use slightly bigger diameter rivets after tapping? BTW, I'm not argueing, just asking, as I've come to hold your opinions in high regard !