Shrink fit tool holders

[camminc]

Hi, my name is Randy. Shrink fit is awesome. Been using it since 1998 for HSM'ing. See this site for information, Shrink Fit, Tool Holder Balance and Tooth Pass Frequency.

http://members.cox.net/camminc/

TTYL

[camminc]

See this site, it has an article on Pieces of the Puzzle - Shrink Fit that might explain the basics, Thanks.

http://members.cox.net/camminc/

[Scott_bob]

As RPM increases, so does centrifugal force...

The clamping force of a set screw(s) in the case of a solid holder, and even the clamping force from a collet can be overcome by centrifugal force.

Small end mills have the smallest set screws and therefore the least amount of “clamping force” in a solid holder, yet these small diameter tools use the highest RPM and see the greatest centrifugal force.

Ever see an end mill or drill come out of it’s holder, or break at high RPM? That’s why we need to use bullet proof lexan in those doors… In fact, come to think of it, I’ll order some ¼” instead of the 3/16” thick lexan I have now. As the diameter of the tool or mass increases so does the centrifugal force acting on it, so we never want to see a tool bigger than ¼” diameter flying around inside our completely enclosed CNC machine right?

Some shrink fit holders offer coolant thru channels or even holes.
Having 10k spindles and low pressure (40 psi) through the tool coolant, I have not seen the effect of centrifugal force acting on the coolant coming out of the holder spinning off outward from the tool, thus leaving it dry.
But at 15k, centrifugal force begins to affect low pressure coolant flow.
At 20k, centrifugal force has a significant affect on any coolant flow coming out of a “rotating reference frame” see:

http://observe.arc.nasa.gov/nasa/spa...gal_index.html

RPM’s above 20k you need to use coolant flow that is external to the rotating spindle…

The clamping force of shrink fit holders cannot be overcome by centrifugal force. Practical example: except, when the interferance fit of the tool is not sufficient, as in the case of an undersize tool shank, or a worn or oversize shrink fit holder...