05-04-2020, 06:31 PM
Don,
End mills are not the best choice for holding a close tolerance holes on blind holes, because there is no way to control the diameter. A much better option would be a boring head. That said, I'm surprised you are getting an oversize hole. Normally end mills drill holes a little under size. You must have a bit of a wobble in whatever you are holding your end mill with.
Brass loves a little WW-40 for lubrication if you are looking for the best finish possible.
BTW, welcome aboard.
Tom
End mills are not the best choice for holding a close tolerance holes on blind holes, because there is no way to control the diameter. A much better option would be a boring head. That said, I'm surprised you are getting an oversize hole. Normally end mills drill holes a little under size. You must have a bit of a wobble in whatever you are holding your end mill with.
Brass loves a little WW-40 for lubrication if you are looking for the best finish possible.
BTW, welcome aboard.
Tom
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