Monday, March 3, 2014

McMaster-Carr, Entertain Me!

It took over two hours, but I finished the first grenade.

The runout on the lathe was about eight thous when I checked it. I swapped in the four-jaw chuck and used some hints from a pair of YouTube videos to dial it. First trick; attach the dial gauge to the cross slide; that way instead of fooling with the zero bezel you just turn the cross feed knob to zero the gauge. Second trick; use two chuck handles, and turn the jaws in pairs. This makes it a lot quicker to dial in -- I had it to within a thou or two within a couple of minutes.

Faced, and the plug didn't spin at all. In fact, you have to know where to look to even be able to detect the line. Slipped up a little and turned down the rim .006 too far, but that's okay. And then since I hadn't cut in an angled shoulder when I first turned the thing, and it couldn't be chucked the other way, I set up a cutting bar at an angle and very carefully shaved an angle down until it touched the grenade body.

Used a center before the twist drill for the primer hole, and that may have been a mistake. A larger center drill, and the twist went in without slopping around this time. Then back to a center to add just a slight chamfer in. Except the angle didn't look right, so I chucked in a custom bit someone had ground out of 3/8" HSS and applied it to the inside edge of the hole in another rather scary operation.

Did a couple quick passes to round off the corners of the rim a little and the body was done. The four jaw chuck wouldn't clamp down on my 1/4" brass stock, though, so I changed over to the other lathe which was already holding a three-jaw. I'd used an A-size bit for the primer hole so I could afford to remove ten thou or so of brass getting it back to round. Which I did, chamfered, parted.

And didn't like the look. Chamfer was too bold, and the fit was a little loose.

Band-sawed another short chunk of brass and this time cut it a little larger with a much subtler chamfer. And during parting it slipped in the jaws.

Fortunately the damage was confined to what was getting cut off anyways, so I hacksawed the rest off in a vice, filed it relatively flat, and popped it in. Held okay as a friction fit, but for the final assembly dripped a little superglue in there.

By this time it had been in and out of lathe jaws and my own bags so many times it was looking surprisingly battered. I took some of the damage off with 400-grit emery paper, then followed up with 0000 steel wool, and for the final clean-up toothpaste from the tube.  By that time it was evening and drizzling outside, which make a perfect opportunity to get some "LV-426" backgrounds for a couple of quick photographs.  Which you see above.

Now it is back to the plans to touch them up, rationalize them...and start planning a second grenade build I can record in detail for an Instructable. Or do some paying is about that time.

No comments:

Post a Comment