What size for interference fit

That would be very challenging for me :faint:
 
At least it is easier to turn the rod and get a good outside measurement, than to bore it and get an inside accurate measurement. An ordinary micrometer reading to 0.0001" and HSS tooling will get you there.
 
Investigator said:
I have a .375 through bore, about .150 thick. I need to bush the hole and drill new hole of center to the original bore. Through the new hole will be a shaft that will spin. This will see very light load, being turned with fingers.

What size shaft should I turn?

Everything is simple steel, either CRS or HRS equivalent. I can freeze the bushing in home freezer, heat the piece its going into in a standard kitchen oven, or use a 20T hydraulic press. Also any combination.
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Green locktite will hold it for finger movement.
 
When you move this hole, is the hole going to be fully contained within the insert, or will it intersect the joint between the insert and the parent metal? A crescent shaped pressed in plug isn't gonna stay pressed after the hole is drilled.

Assuming that the new hole is completely contained in the insert, from what you're describing, half a thousandth or less would probably do the job fine. If you're banking on the press fit holding during the re-drilling process, you probably want more. Maybe one and a half thousandths of interference. Might even get away with two. For drilling loads (within reason, which a hole in that size range probably is), Loctite 603 or 620 would do magic. They wouldn't save the say if the fit was wiggly, but would do the job very nicely even if the insert could press in with your thumb. As would ten thousand other retaining compounds (not threadlocker), and there might be better, but those are the ones I can get my hands on easily, and either will do well beyond what you're describing.
 
Thanks for all the suggestions. I ended up turning a rod down in steps to have several diameters from .382-.376, each step was .002 larger than the next. I pressed it in with my 20T press until I couldn't press any more.

The hole will be completely contained in the plug.
 
benmychree said:
I'd consider a slightly shallow straight knurl on size instead of an interference fit, or size on size with loctite.
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This strikes me as a good plan, or at least backup plan to cutting 0.0002" over. You're not only looking for an interference fit (for the outside of the bushing), but you need a sliding fit on the inside, which means too much external interference is likely to ruin the sliding fit. I'd try for the "right" thing first - after all it's pretty cool to hit a dimension to tenths, but a knurl is a quick and near certain way to recover if you miss.

GsT
 
GeneT45 said:
This strikes me as a good plan, or at least backup plan to cutting 0.0002" over. You're not only looking for an interference fit (for the outside of the bushing), but you need a sliding fit on the inside, which means too much external interference is likely to ruin the sliding fit. I'd try for the "right" thing first - after all it's pretty cool to hit a dimension to tenths, but a knurl is a quick and near certain way to recover if you miss.

GsT
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Im going to drill the internal hole after pressing in the 'plug'
 
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