"Harold and Susan Vordos" wrote in message
...

"PrecisionMachinisT" wrote in message
...
snip-

Any chucking reamer has an inherent back taper designed and ground about
the
diameter....generally its ~.002 / inch--and as such, they certainly *do*
lose a bit of diameter *each and every* time that you re-sharpen them.


While chucking reamers do have taper as you suggest, it is much more
gentle.
Typically, a small chucking reamer (3/8", for example) would have about a
half thou taper in it's entire flute length.

You can usually tell if a reamer has been reground by checking the shank,
between the flutes and the area used to grip the reamer. Taper for the
flutes is generally set there before grinding a reamer to resize it. That
way one can alter the size of a reamer by tenths with no risk of ruining
its
size while making the proper setup. As I said, I've reground a large
number of reamers in my day, and that's the process I was taught to use by
my mentor, who had spent his life time in the grinding room.

Because chucking reamers cut on the chamfer, Dave is somewhat right in
that
you can sharpen them time and again and not lose size, but you're limited
by
the center hole on the cutting end. As you repeatedly sharpen them, you
run into it, so you have to lose the center hole---but by then you
generally
are satisfied that the reamer cuts the desired size, so it's no big loss.


Harold,

Okay, I'll buy that--I just miked one and it came in ~ .0005 / in.
backtaper....

When you think about it, a reamer *can't* work properly with no taper--all
you have to do here is consider in theory what would happen if the taper
were reversed....tapered hole and entire flank would drag........

Mainly I saw the opportunity to harass Dave a bit and just *couldnt resist*
the temptation......my main point being that size is *definately* changed on
sharpening a reamer--not much.....but still it *does* change, this being
contrary to his claim......

Now the .002 /in number I came up with is something I generally specify when
modifying an endmill for plunge-boring holes as a pre-reaming op....I musta
got that mixed up with standard reamer taper for some reason is all.

Cheers,

--

SVL