On 4/14/2020 5:49 PM, Jim Wilkins wrote:
"Bob La Londe" wrote in message ...

I'm looking for a tiny threaded collet. ER collets are fine, but you
can't really use them to make long reach tooling. Shrink fit is an
option I guess. My goal is to make my own mold making tool holders to
use modest price proper geometry end mills in long reach applications to
have greater rigidity than a long reach mill and better cost
effectiveness than a tapered end mill to achieve that. I know. I know.
It already exists in some types of tool holders,but I want to make
something a little more universal to fit into tool holders I already
have. Harvey tools makes an end mill extension, but their current
version isn't tapered or designed quite right for what I want. I could
buy them and maybe modify them, but they aren't cheap. Mostly I am just
thinking out loud right now. I recently picked up a surface grinder,
and I am making plans for making a cylinder grinding attachment for it.
It would be ideal for finishing hardened tool holders like this.

Might actually use some of my grinder vises like they were intended.
LOL.
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If you make extensions with integral collets by slitting them
crosswise, the closer nut could have tapered pipe threads.




The idea is to have maximal support for smaller mills when deep
machining. I would prefer in internal draw bar to an external closer
nut I think. I did a search for "straight shank end mill extension"
just a few minutes ago and found quite a number. Most use set screws.
One that came up in image search showed a collet, but when I went to
their website it they just showed a set screw type.

These would only be useful for pockets with a lot of draft angle or a
feature of the floor of a pocket, but I just finished an open casting
mold with pretty deep pockets and tool deflection affected finish
quality with a lot of tool stick out. I had to slow the job down a lot.

On the other screen I am working on a rough model. With a 3/8 Ball mill
for the angle I needed with clearance I could have just one inch of
stick out and be upto to 5/8 shank. Of course I could just continue the
taper as far back as I want to fit into the largest tool holders I have.

Once I have it dialed in to make them I could make ones with a little
more slender profile for tiny mills and less available angle clearance
too. Of course its all a trade off.

I recently engraved the bottom of some deep pockets with a company logo
using a 1/16 ball nose end mill. A tool extension sized for this
application would have allowed me to feed much faster than I had to run
with the ER collet tool holder and the long reach end mill I had to use
to do the job.

They will not be a magic cure all, but they would speed up many jobs and
improve surface finish doing it.