Earlier this year I had to replace a set of bushings on a Sprite spindle. The bushings have to be line reamed to size after install. Reamers are sort of commercially available but expensive ($300-1000). I knew of one or two vendors that allegedly did the service but it seemed worth trying the DIY route first since there are several of these cars within the circle.
I started with a piece of annealed W1 bar stock, added a hex for a wrench, and turned the soon-to-be cutting surfaces to 0.0005"-0.001" larger than the journal.
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I first drew the flutes in CAD to help get the spacing correct. Next they were cut using a 1/2" carbide endmill.
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I initially added a small pilot at the start of each reamer in the hopes that this would create enough of a cutting surface. The first attempt failed and it was back into the lathe. I removed more material and hand sharpened the flute tips with a file. A quick test yielded some chips so this seemed like it had a chance of working.
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The last step was to heat each flute until orange started appearing and swishing it around in water. Following hardening, everything was annealed to remove some brittleness.
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And for the moment of truth.....
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I'm calling it a success. I am still not sure how it would work on harder materials but this process definitely works for softer stuff like aluminum, brass, and bronze.