On Tue, 08 Mar 2016 10:58:57 -0500, Neon John wrote:


Hey gang,

My company manufactures induction heaters. We've sold a number of
heaters to CNC shops that use shrink-fit tool holders in their CNC
machines. We supply the RF source and they make the jig to hold the
collet and tool. So I've never seen an actual collet.

I want to make a setup for my salesmen to demonstrate shrink-fit
tooling replacement.

Several questions.

What would be a typical interference fit between collet and tool?

Would it be cheaper to buy a collet and say, end mill than to have
something made?

What should I expect to pay for a collet (are there various sizes?)
and where would I look to source one.

Are the collets standardized across the industry or does each CNC tool
maker use a different design.

Anyone have a damaged, worn-out or otherwise unusable collet they'd
like to donate to a worthy cause? Shipping and handling gladly paid,
of course.

Thanks,
John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address
Greetings John,
The tools are held in a tool holder, not a collet. A collet fits
inside a collet holder of some sort and then a tool fits inside the
collet. With thermal shrink fit tool holding a tool holder is used
without a collet, the tool fits directly in the tool holder. The tool
holder will have a taper for fitting into the machine spindle. I don't
remember what the amount of interference is but it is quite small.
Over time after many cycles of heating and cooling the I.D. of a
particular tool holders will expand and so the holder starts losing
its grip. Some shrink fit tool holders use special cutters that have a
helical groove machined into the shank. This direction of the groove
causes the tool to be drawn into the holder from cutting forces trying
to cause the tool to spin in the holder. Your best bet is to look for
a tool holder on eBay if you need to buy one. If you search for a
"shrink fit tool holder" on Ebay you will see several new holders for
less than $150.00. Since they start to lose their grip over time one
of your customers may have one that they are no longer using. Even
though the grip is too weak for machining it should be good enough for
demo use.
Cheers,
Eric