Would a new handheld file be too slow? Would an angle grinder be too fast or too hard to control? I have both, and thought about mounting the grinder in a bench vise.
Opinions?

 

Buy the correct jigs/tools for gapping. You'll be glad you did.

 

Pretty cool video with the grinder/Jigs

 

You can also cheat and get a cheaper hand-crank style, cut off or remove the hand cranker, and attach a cordless drill to it. Presto, powered ring file. Just, uh... Be careful. It goes a lot faster than you might think.

How much do you need to take off the rings?

 

As mentioned you will want to buy a ring gap grinder tool. Hand file won't cut it not will a grinder. You need to ensure you are removing material square to the cross section of the ring. Meaning, no bevels, radii, etc.

 

About what I expected, where's the fun in that? I ask myself, what would the sloppy mechanics do? I'll try the hand file first and report back by posting a link to a video I'll post to YouTube.

 

A good abrasive will have no problem, a die grinder set at low to medium speed in a vice with a finer type of bit, recheck gap and finish with sandpaper. I do amateur machining and sounds a little scary for a high pressure, temperature sensative, tolerance limited application, but it's not impossible. Would be impressed if you could pull it off and make all of them to within tolerances without driving yourself crazy. Look for a local machine shop supply tool warehouse and grab some good quality grinding/sanding bits/wheels,discs,belts.. whatever works for you.

Trying to do that with some **** from home depot would make a murderer out of a lot of people.

Oh and don't get it too hot. If they're a type of cast iron they can get very brittle.