I need to ream an aluminum piston and bronze rod bearing to match the wristpin. Will be taking a very fine cut (around 1/10 of a thousandth). Should I use a lubricant on on the bronze or aluminum? If so what lubricant(s) should I use. I am using a hand held adustable reamer
While there is some risk of creating a lap from imbedding abrasive from the hone, it would be the method of choice in this instance. Pistons are honed routinely, but with rigid hones, such as a Sunnen. Properly applied, they don't leave anything behind that would be a problem. Stones used for soft materials should be hard bonded and break down very slowly. The steel shoes opposite to stone more or less constantly are wiping the surface. Virtual no abrasive ever leaves the stone, so as long as the honing oil is clean, it would be the method of choice.
The problem you're going to have with a hand reamer is cutting an out-of-round and oversize, tapered bore. When you start talking tenths, reamers become very suspect, especially hand reamers. If your project is a one that would suffer serious consequences should you fail, I strongly suggest you take it to a shop that is properly equipped and have it honed. Assuming you have a mating piece, be certain to provide it so it can be fitted properly.
I also strongly suggest you not try a wheel cylinder hone to remove any material. They don't have the means to control straightness or roundness the way a rigid hone does. That would be a sure recipe for failure, much like a hand reamer.
Find a ball bearing of the proper size and press it through if you cannot have it honed on a Sunnen hone. Hand reaming is gonna leave a nasty hole that will NOT be round or true.
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