"Tom" wrote in message
...
PrecisionMachinisT wrote:

"Tom" wrote in message
...
PrecisionMachinisT wrote:

"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,

..............................
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......
..........................

Cheers,

--

SVL

If what you is true, there would be no point in sharpening reamers,
fortunately it isn't, machine reamer manufacturers cylindrically
grind the lands of the reamer to the true size for a distance,upwards
of .32", depending on diameter, adjacent to the bevel cutting edge.
That way the reamer can be sharpened a number of times before the
sharpening process incroachs on the back taper ground section of
the body. This "true" diameter also acts as guide & pilot for keeping
the hole in line..


And just where did you get this information from ???

--

SVL

LOL, it was part of my formal engineering education..
However I did consult today, a Dormer twist Drill &
Reamer Handbook, to ensure that what I was taught &
learnt was correct.

Apparently I was a good pupil. :-)


Then Dormer may well be an exception to what is generally found in the
field--I actually measured quite a few reamers new out of the box today,
from various reputable manufacturers and even found a several that got a few
tenths bigger going up the shank.......

Preferably, and in most cases I would want the reamer to back taper all the
way--if not, they will often produce a poor finish in the softer materials,
as well as burnishing and possible tearing in the harder materials--this
something I have had to battle many times over, esp. in reaming hardened
steels like 4140 and what not, using carbide tipped reamers.......even to
the point where I eventually quit reaming altogether and instead opted to
use a boring head.

--

SVL