Took the SBU (Safety and Basic Use class) for the MIG welder last week. Went in today and pulled a bunch of scrap (mostly battered welding chits from previous classes) from the bin and tried to remember what I'd learned in class. I'd had a lot of trouble in class for some reason. I think because previous experience in stick welding had me used to eyeballing the arc, and the bulk of the MIG electrode holder means you really can't do it that way. So fifteen years of muscle memory was in my way.
I messed with the dial settings and made lots of nasty spots and sputters for about an hour, then it started to click. The "bacon" sound came almost immediately upon achieving a good spark coil sound (the two sounds are superimposed; you can hear when you are getting a good weld). And once I found that groove, I could pretty arbitrarily change the electrode distance and travel speed, pretty much adjusting one to the other.
It is a whole dance when you are doing it right; maintaining the arc, building and pushing the puddle, achieving the right blend of penetration and fill, controlling the heat build-up. All through constant movement whilst maintaining the correct distance and travel.
Put rougher scrap on the table and started at welding into corners and filling voids. And it was going well enough I jumped right up to working on the Suomi again.
It is nice to finally have the receiver in one piece. There's a lot of grinding and filing before I can be sure I got the measurements right, though. And I haven't decided on the best way to tackle that hole behind the magazine well. I could mill a backing plate out of aluminium plate and fill the remaining void with weld metal. Or I could cut a slot and put in new steel. Or perhaps I can mill down the stubs of the side rails enough to where I can slot in new chunks of plate steel -- probably again with a backing plate of aluminium.
I also think I have to lathe another "fake bolt" to use as a backing plate to put a little more metal at the end of the tube; the cap screws down only so far and the gaps I have would be visible in the assembled weapon. The original fake bolt I machined is of course welded permanently inside the tube at this point, and I intend to take further steps to ensure it remains so.
There's still several smaller gaps. I tried flowing solder into some of the smallest holes but my iron hasn't got the power to push heat into five pounds of steel. There's also an epoxy-based filler designed for this, but it doesn't take bluing well. I have a small brazing kit, too, but unless I get in on the TIG class some time real soon I'm looking at basically throwing big blobs of metal from the oversized wire we have and then grinding them back down again. And it may take multiple passes before I'm satisfied with it.
In any case, TechShop was very much the way to go. Sturdy steel tables, lots of clamping options, a full-sized MIG of course, and lots of bandsaws and grinders and whatnot right there to create filler with. Much more comfortable than the plywood propped up on sawhorses out in a parking lot that I started with!
It is nice to finally have the receiver in one piece. There's a lot of grinding and filing before I can be sure I got the measurements right, though. And I haven't decided on the best way to tackle that hole behind the magazine well. I could mill a backing plate out of aluminium plate and fill the remaining void with weld metal. Or I could cut a slot and put in new steel. Or perhaps I can mill down the stubs of the side rails enough to where I can slot in new chunks of plate steel -- probably again with a backing plate of aluminium.
I also think I have to lathe another "fake bolt" to use as a backing plate to put a little more metal at the end of the tube; the cap screws down only so far and the gaps I have would be visible in the assembled weapon. The original fake bolt I machined is of course welded permanently inside the tube at this point, and I intend to take further steps to ensure it remains so.
There's still several smaller gaps. I tried flowing solder into some of the smallest holes but my iron hasn't got the power to push heat into five pounds of steel. There's also an epoxy-based filler designed for this, but it doesn't take bluing well. I have a small brazing kit, too, but unless I get in on the TIG class some time real soon I'm looking at basically throwing big blobs of metal from the oversized wire we have and then grinding them back down again. And it may take multiple passes before I'm satisfied with it.
In any case, TechShop was very much the way to go. Sturdy steel tables, lots of clamping options, a full-sized MIG of course, and lots of bandsaws and grinders and whatnot right there to create filler with. Much more comfortable than the plywood propped up on sawhorses out in a parking lot that I started with!
Came home, and my laptop was showing that it was on battery. With the charger plugged in. Oops. Looked at the charger, and there was a nasty charred spot in the cord where somehow it had cracked or been caught (or nibbled?) and tore the outer wrap-around conductor. Which apparently is not a ground/shield; there's power running through it. Hrm. Anyhow, was able to work a length of desoldering braid into the frayed ends and restore continuity. Good thing, too, since closing weekend is almost on us and all my sound cues and keyboard patches and house music are on this machine!
To finish up the day, plugged the UMX-610 into a Reaper file I keep for that purpose and did a little piano practice. But what did I say about muscle memory? Maybe welding all day tuned my hands to the wrong expectations. I was fumbling a lot of notes. But oh well. I do far too many things to even hope to do all of them well.
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