question about the effect of welding on the locking recesses

[trenches]

I'm wondering about what effect the heat of welding would have on roller locking recesses. I know the originals were welded so it's shouldn't be a problem. Heat is heat no matter where it's applied, here or in Spain.
I used heat sink paste when plug welding the holes. When I welded the rear of the trunnion at the slots in the receiver I used a heavy piece of copper into which was inserted a section of old 8mm barrel stuck inside the rear of the trunnion. This should have siphoned enough heat off so as not to effect the trunnion temper.
So what do other guys use when they are welding the trunnion to the receiver? Just curious.

[turbothis]

i would like to know the voodoo of this too. if it where mine i would blast it and find out. but that is only me....

[bolex]

I'm wondering about what effect the heat of welding would have on roller locking recesses. I know the originals were welded so it's shouldn't be a problem. Heat is heat no matter where it's applied, here or in Spain.
I used heat sink paste when plug welding the holes. When I welded the rear of the trunnion at the slots in the receiver I used a heavy piece of copper into which was inserted a section of old 8mm barrel stuck inside the rear of the trunnion. This should have siphoned enough heat off so as not to effect the trunnion temper.
So what do other guys use when they are welding the trunnion to the receiver? Just curious.

Carefully TIG weld the receiver to the trunion. The receiver is not heat treated so no worry about that and you need to minimize the heat going into the trunion. The trunion has a fair amount of mass to distribute heat into. Just do one weld at a time and let the trunion cool down between welds. This is one reason to use TIG over MIG, better heat control.

[okie shooter]

The less heat you can apply the better for sure, when welding the truniion to the receiver. The thing about what they did in Spain and Germany, and I imagine in Vermont too, is use of a spot welder which will localize the heat, infact the electrodes are even cooled in industrial welders, its the resistance at the surface that gets the nugget red hot, but its very localized. Thus to do a receiver I would drill holes in the receiver and fill with MIG or TIG with wire to refill the hole and make the nugget solid with the trunion. IMHO though, I didnt stay at a Holliday Inn Express last night, and its been far too long since my three semester hour metaluargy course, and the three more semester hours of Machine work and welding.

[trenches]

It would seem that with the barrel attached that would also act as a heat sink. My barrel was warm to the touch, not hot, but warm. So I believe that some heat was siphoned off by that. Same with the receiver. The only area that was hot was the immediate area of the weld. Also the Calgon heat sink paste I used absorbed a lot of the heat.
I would think that there would be reports of the guns blowing if welding was a bad idea. Think about how many Cetme's have been built by guys welding the receivers. Does make one wonder however.
As I finished a weld, I left the paste and the copper in the trunnion which should have continues to bleed off the heat from the weld. Let's face it. when you weld, you can't avoid getting that area hot enough to melt. After all, that's what welding is. Fusing to pieces of metal together by melting them. That takes a lot of heat obviously.
I was at Arizona Response Systems. He has a short tutorial on welding the trunnion to the receiver of a Cetme. He makes no mention of using a heat sink except for the cocking tube. He tig'd his receiver and trunnion. Building Cetme's and HK's is one of his services. So I imagine if welding by tig or mig was a problem he'd know about it.
Also. We all know how hot the barrel of a rifle can get if you fire a lot of rounds in a short space of time. Especially you bump firing guys. If you can melt the forearm off of an AR-15, I'd say that you had the barrel and receiver pretty hot.
In any case, I'll find out when I shoot the Cetme once it's done. I don't think that I'll need a tire and a long string when I do however.
BTW, just for the hell of it I put the Cetme together minus the fcg parts. Although the cocking tube isn't welded yet, the bolt still unlocked when I pulled back on the cocking handle. The bolt slid into battery without hanging up. That's a plus. But I did have to expand the sides of the magwell to get a mag to enter. This weekend I'll clean the welds up and clean up the rest of the receiver and then install the mag latch.
I have to complete fitting the hammer and sear that I made yet. Once the engagement surfaces are fitted I'll caseharden them. That should just about so it except for tweaking. it to cure any problems that might arise.

[bolex]

....I have to complete fitting the hammer and sear that I made yet. Once the engagement surfaces are fitted I'll caseharden them. That should just about so it except for tweaking. it to cure any problems that might arise.

Can you post a photo of your Cetme hammer you made? I made a trigger and the trigger box, and just wanted to see a home made hammer to get a feel of the complexity.

[trenches]

Right now I can't post a picture. But it is an exact copy of the Cetme's. I marked and drilled the hole for the pin. Then using the original as a template I cut out the new one. I inserted a drll through the hole and used a clamp to hole everything in place until I had an outline scribed. After cutting to the rough outline, I put the drill bit back in and then clamped the parts together again in the vise. Using the original as a guide, I then filed away everything that didn't look like a hammer. Just don't file into the original. Same with the sear. That slot that holds the interrupter was a pain to file. I'm using 1018 low carbon steel which I will caseharden once the final fitting is done. The 1018 will take the shock of being slammed home on the firing pin. Smith and Wesson fcg's are casehardened also. If it's good enough for them, it's good enough for me. I was going to use O-1 tool steel but I thought I'd try the 1018 first. I'd like to use 4130 or 4140 but I can't find any in the size I need.
I'm also making a charging handle and possibly the trigger. So you see, I've got my work cut out for me. Pun intended.