Thread: An idea for a contact grinder.

Nice looking washer. Maybe try using some compressed air to blast it out of there? May be more trouble than it’s worth though if you’ve got washers flying around the shop.

Originally Posted by jfk742

Nice looking washer. Maybe try using some compressed air to blast it out of there? May be more trouble than it’s worth though if you’ve got washers flying around the shop.

After posting, I went back down to the workshop and played around with it some more. The idea I had up there of punching washers, then punching centers does work, and they’re really easy to get back out (though steel sticks in there because the die is slightly magnetic for some reason).

Better still, I figured out how to just probe around a little with that center punch and get it to push the washer out after the first go. Sometimes need to fish it out with needlenose pliers because of the magnetism, but it’s not so bad.

I also tried using some 26 gauge galvanized steel sheet and that worked even better.

The end result?

I ended up making a new center punch for this setup and it works much better. It can be tapped in with a rubber mallet too, so there's really no danger of deforming it.

Because I'm heat treating with a general purpose propane torch (why haven't I gotten a MAP torch yet?), the HT on the part isn't super even. I don't think the part that gets pounded is particularly hard, but the business end is impervious to a file, so all is well.

Now I wanna make all the parts over again, but better. Having gotten it all to work, I have a much better idea what I'm doing.

Had a banner day of Craigslist shopping today. Bought a 1950's toolbox that belonged to a machinist that worked on nuclear submarines. Got a bunch of HSS lathe bits ground to purpose, some end mills, some shaping & polishing stones, a hardened machinist's ruler (that needs some love, it's got a couple bad rust spots), and two micrometers. I've been wanting a quality mike for a few months now.



The larger of the two is a Reed Small Tool Works from the 1920's (from what I can tell). It's a 2"-3" with ten thousandth accuracy -- unfortunately, it's in desperate need of a calibration and cleaning. It currently closes on 33,000ths.

The smaller one is a Brown & Sharpe circa 1950's. There's a calibration sticker from 1970, and it seems to be on the money. I'm very psyched!

Also included was a personal inventory of tools, when they were purchased, how they're identified and how much was paid. It all ranges from 1952 (the toolbox) to 1970. Plus a filled-out procedure test for working on nuclear subs!

There's all SORTS of stuff in there. Ball bearings, pen nibs, grub screws, scraping tools, mysterious carbide insert tooling, precision sawblades, boring bars, blank HSS lathe bits. Dirt. Rust. That 'old machine shop smell'.

I've got on order right now a collet chuck for the lathe because threading parts was starting to drive me completely mad. These power-punch style screw-in dies need to be flipped a couple of times in the lathe and the standard three jaw chuck on my HF lathe is giving me fits matching concentricity. It's really just "open chuck, turn part, roll dice". YOU LOSE, TRY AGAIN. Feh. Three jaw chuck.

Originally Posted by Voidmonster

It's a 2"-3" with ten thousandth accuracy -- unfortunately, it's in desperate need of a calibration and cleaning. It currently closes on 33,000ths.

I don't understand this statement. If it's a 2-3" mic, don't you need a reference block to check the calibration.

Originally Posted by bluesman7

I don't understand this statement. If it's a 2-3" mic, don't you need a reference block to check the calibration.

It might be a bad assumption on my part, but when the barrel is screwed all the way down it reaches an immediate, firm end. At that point, it reads something like 33,000th's. The system it uses for 10 thousandths is entirely unfamiliar to me, but it stops close to a line between 0 and 5 thou.

Yes, there should be a piece that is exactly 2 inches long that is used for calibration. The only one that does not need one is a 0-1 inch mic, in that case it is screwed all the way down till the anvils touch and then is should read zero. (actually the same is true with the 2-3 only you will turn it down to the calibration piece.)