Wednesday, March 13, 2013

Jet engine project - Part 3

After spending several nights experimenting with some ghetto homemade tooling to bore out my replacement main journal bearing, I couldn't rig something that gave a smooth enough surface over the length of the bore. So reluctantly, I took it to a reputable machine shop to see if they could complete this step for me. Surprisingly, they fared no better despite three hours of trying. Worse, now the bore hole is about 0.001" larger than I'd like and a bit rough. Can't fix that! What a bummer, because I'd managed to machine the outside to within 0.0002" of the original part.

So much for "saving money"... now I'll just buy the tooling myself and have another go. That means making a new bearing from scratch. However, this time I'll start with the borehole and work to the outside. There's still the question of how to accurately mill the end cutout without a milling machine. I may be able to do that on my drill press--slowly. It's only brass, after all. None of this stuff would be a challenge on a CNC lathe but it's surprisingly tricky to do on a manual lathe. I've even tried maple jigs for offset turning the end mill. I could machine the maple to within a few ten thou of runout, but just could not get a decent interrupted cut in the brass with my makeshift tooling.

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