Went in today. First task was to find a way to hold one from the other day that I'd forgotten a cut on. And then I cut too deep. Drat.
Ran off a second solid-body and was starting to get into the groove. Set up for the finishing pass, threw on the half nut for a powered feed -- and engaged the cross-feed instead of the longitudinal. Drat. Fortunately, this time I knew I could rescue the piece as long as I didn't re-chuck it. So turned it into another full-function body. Of course, that meant bringing out a bunch of other tools, and pretty much killed the assembly line.
Then ran short of metal. Was just enough on the last bar to finish the order if I was clever. I wasn't quite clever enough. Did two passes in the wrong order. Set up for a left-handed cut, got the power feed set correctly for that. And going "backwards" must have thrown me, because when it came to the moment where you throw off the half nut and take up the motion smoothly with the traverse wheel...I grabbed the wrong wheel. Drat.
Oh, and finished the day destroying another chunk of brass stock trying to part it. At least this time I figured out a better method; just cut a v-groove where the part should happen, and hack-saw it off right in the lathe.
Next set, in progress; the solid-bodies need to be painted, the two full-function need the spring-loaded buttons installed. Unfortunately, all the primers I ran off yesterday are a trifle large; only two of those in the bag were useable. The two grenades on the right are mistakes; my original (at the old dimensions), and the one I tried to rescue and failed.
The one thing I can say is I'm starting to like that 7075. It is very springy; I have to adjust to the tools springing back on me, and dealing with chips on the rough passes is still a problem. Also, it is so tough I can't really dig the knurling in as deep as I'd like on the grenades. But on the upside, with the right feeds it makes a very shiny, hard surface. It feels tougher, and even weighs noticeably more.
I've been looking at the Suomi some more. The plasma cuts they made through the receiver left some pretty large gaps. Just welding isn't enough; I'd need to do filler welds to bridge those gaps. And it also made a total mess of the threads where the end-cap goes.
But machining is no simple task, either. There's a lot of complex slotting for the magazine well, and some big chunks of metal that need to be constructed for that, too. And it seems impossible to do without welds -- which means getting checked out on MIG, and then getting enough practice in to do them clean.