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(DoN. Nichols) wrote:

In article ,
Bruno wrote:
Thanks to all who replied to the original post.

The part is a tool holder for my lathe, hence the need to clamp and
unclamp it repeatedly. There was a lot of milling, drilling and
tapping that went into the pieces before messing them up, so salvaging
them was desirable.

[ ... ]

I made a jig that allowed me to put the part on the lathe and I bored
the rest of them that way and it worked beautifully. Problem is that I
have a bunch that are in need of work. Sounds like the only realistic
approaches are 1) find a way to slit them wider and hope that works,,
2) boring the hole a bit wider and machining a sleeve that can be
permanently installed into the hole, or 3) tossing them.

I see a fourth option:

4) Make a new post (the cylindrical part, which might be easier).
That is only *one* part to make, instead of a half dozen or so.
Make it a little oversized, and bore *all* of the holders (the
ones which came out right and the ones which did not) to fit
that one. I would suggest boring one of the bad holders first,
to see how much is needed to make it clean up.
I though of this too, but then I'd have to redo all the original
holders as well, and I don't want to do that (and they are probably
already hardened). And I don't want two post sizes; the time to
change a post would be more than the time to change a tool in the
holder. But I will reconsider this decision as it can't hurt if I'm
tossing 'em anyway.

Out of curiosity -- what kind of endmill was used for the failed
attempt, and did you have a hole drilled through the center of the
workpiece before you hit it with the endmill? Most endmills that I know
of that size are not center cutting -- at least ones which will fit *my*
machines. Those which I have only have the end teeth going about
half-way to the center, and then there is a recessed area with a female
center for additional support while sharpening the endmill. Thus, for
these, a hole about half the size of the endmill OD would be needed
before you tried the endmill itself.
I'd drilled up to 1/2", then used a 1" 6 flute endmill and had a good
hole there. It was just the final 1 1/8" cutter that was bad. It was a
different type with three flutes. It was the only cutter of that size
in the shop and the teacher said it should work fine. I realized later
that I'd have been better off to have left it at the 1" and bored the
last eighth at home on the lathe, but I hadn't tried one on the lathe
yet, and of course hindsight is clarity.

Good Luck,
DoN.