"Ed Huntress" wrote in message
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"Jim Wilkins" wrote in message ...

In my limited experience D bits are tricky to sharpen ...

-jsw

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[Ed]

There are several configurations of drill bits and reamers that are
called "D-bits." It sounds like you're making the kind with a center
point. They're a b**ch to make, as you suggest. I've had much better
luck with the simpler kind that's flat on the end.

I learned to make these from the old English MAP hobbyist books,
which describe several types. This article from a 1967 issue of
Popular Science describes D-bits pretty well:

http://tinyurl.com/qdcnuoa

--
Ed Huntress

That version is easier to make than the ones in Lindsay's "Deep Hole
Drilling". I stop at the step where the lathe tailstock needs to be
aligned, since trade school apes misused the original spindle on my
lathe as an anvil horn. The dealer swapped it but the replacement is
loose, drill bits visibly jump up to the center of rotation when they
bite into the work.

Centering with one of these center drill collets instead of a drill
chuck helps a lot:
http://www.collistoolholder.com/cgi-..._9_TYP_Q_GRP_1

-jsw