Machining stainless steel at home?

I have a stainless steel* split shaft collar type item that needs to be embiggened. Its inner bore is 1.25" now, but I need to increase it to 1.35" and the thing is 0.6" thick.

As a one-off thing, am I insane for thinking I could do it a half-round file, or can I put a 1.25" sanding drum with an appropriate abrasive in my drill press and wobble the thing around to make the hole larger? Or a cylindrical grinding stone? The ID is not concentric to the OD, so just chucking the thing on a lathe to buzz off that tenth is not happening.

*No idea what grade, probably 304. Not magnetic.

You could try the file, see if it bites into the SS. If I’d does you should scribe a circle of the final size so you can file like a madman during the roughing phase, and slow down and use more care as you approach the final size.
There is a reason we called it “Fuckin’ Stainless” when we had to work with it in the machine shop.

It’s a split collar so you just need that to be tight on the shaft, you don’t need a perfect bore, right? Try the file, it’s going to take a while though. A carbide burr bit in your drill press might help remove some material quickly to start with, not sure what kind of speed that requires. A sanding drum will probably take longer but be easier to control. It’s really about how much patience you have.

Moving this to IMHO. It could potentially live in general questions, but i think a lot of the answers you might get will be people’s personal experience with similar situations, so i think this is the best home.

We made molds for the lenses in pinball machines out of 420 stainless. We had to drill 1/16” holes in two inch thick blocks to serve as start holes for the WEDM, wire electrical discharge machine. Stainless will work harden in a heartbeat if your cutter is rubbing. When you stop making chips you stop tool pressure and sharpen or replace the cutter.
I hope you have a bench vise on a sturdy workbench because a rigid set up is also key to machining stainless.

That is what the 4 jaw chuck is for. Get to a lathe. The 4 jaw will center it up.

If you’ve got a cutter/grinder that’s anywhere close to the ID of your shaft, and spinning at any appreciable speed, and you don’t have your part firmly fixed, there’s a risk that your part could start whirling violently around the cutter.

OTOH, shaving off that much stainless using hand tools is going to be a mind- and hand-numbing process.

Maybe you can find a local machine shop, and pay them to do it on a four-jaw lathe? Might cost you an hour of their time, so maybe $100. It might be worth that to avoid what would surely be a painful DIY job.

I hope they would be nicer than that. 100 thousandths? A good machinist would have this part in the 4-jaw chuck, dialed in, bored, and deburred in about 10 minutes.

I guess a job shop probably works like a auto repair shop, rounding up to full hours, but it seems like if you catch the guy on a good day it wouldn’t cost all that.

Got any friends with a metal lathe?


I picked up a cylindrical carbide burr and on one half, I was able to raise the drill press table and swing the thing around to chew out most of what I needed. I just ran a red Sharpie along the edge so I could keep track of progress. Dummy me, I forgot to mention that the other half has a permanently attached rod along the axis, complicating things. I wound up clamping the rod in a bench vise and using the burr in a drill. Think that actually worked better than the drill press.

Then some work with a small sanding drum in a Dremel to smooth out the bumps, and Bob’s yer uncle!

Would I want to do this again? Oh heck no! But at $11 for a burr and some time, I got what I needed. And probably faster than calling around with “Hey, I got this chunk of stainless…” and getting into a shop’s schedule.