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  1. #13
    Join Date
    Nov 2017
    Quote Originally Posted by hanermo View Post
    I suspect what you want is a carbide reamer.

    Since you seem happy with interpolated holes, I also suspect you don´t achieve 0.01 mm +/- in size cylindricity and straightness.
    Do you have go / no go gages of 0.01 mm size difference to qualify size and straighness of the holes ?

    No Q. intepolated holes can do 0.01 mm, but on high end machines with industrial tooling.
    Yeah, +/- .01mm diameter and round was a bit overstating. That's what id like to shoot for, but doesn't need to be quite that perfect. Let's say +/- .015mm. The holes that I interpolated with spring passes were measuring 4.33 to 4.34 at different positions, probably .01mm oblong in many cases and an occasional 4.32 and 4.35. This was accurate enough, just a pain to keep chasing the cutter wear. When I get the couple bits I ordered, I'm gonna throw the 4.305 in a cheap Chinese collet I have with some runout and see what the hole looks like. If I can push a 4.32 pin in it, I'm calling it good enough

  2. #14
    Join Date
    Nov 2017

    Re: Slightly sizing down a carbide drill

    So I ran the 4.305 bit in some holes. In one of my old cheap collets I got it chucked up with about 7 tenths runout. Worked great. 4.32 pin passes, 4.34 does not. Close enough. Not very scientific, but it works. Obviously an average drill bit would just center itself, but at only 10mm long flute and 165deg point, it seems to hold the runout and enlarge the hole.

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