WeTeamUp Terms: “Shank”



What’s a “Shank”?

The shank is the part of a milling tool that is held in the machine’s collet – opposite of the cutting end. The importance of the shank is often overlooked. It’s responsible for centering the tool in your machine’s spindle. A poorly made shank will make the tool wobble (runout) while it cuts. Runout is directly related to tool life, and the fit/finish of your units. The production quality of the shank directly affects the performance and longevity of the tool.

Interesting details about “Shank”

Critical reference point

The shank of the tool is a critical reference surface. The internal surface of the collet and shank must be precisely matched to ensure that the cutting end of the tool is concentric with the spindle’s axis of rotation. Any deviation from the spindle’s rotational axis will result in runout, which will reduce tool life and milling quality. The ideal shank is perfectly round and straight. If it’s not, it won’t clamp into the collet correctly and will perform badly. Well made tools control the roundness and taper of the shank to extremely tight tolerances (Sierra tools hold an H4 tolerance, suitable for aerospace applications).

Surface quality matters

The surface prep of the shank affects how securely it can be held during milling. Many tools on the market have a polished finish on the shank. While this is aesthetically pleasing, it degrades the performance of the tool because polished surfaces are slippery. Tools with polished shanks are not held as securely in the collet, which can cause tool slippage and poor milling results. Sierra tools have a matte “no-slip” shank surface that ensures proper clamping.

Cleanliness is important

Some dental machines are prone to tool slippage. You can help avoid this by keeping the shank and inside surface of the collet very clean. We recommend wiping both surfaces with alcohol to maximize the collet’s holding power.

Thanks for reading! We hope this break down of the term “Shank” has been of value. Stay tuned next week for another post like this!


Check out the growing list of WeTeamUp Terms posts HERE

Published by

Greg Everett

Hi, I’m Greg Everett. I managed a milling center in Southern California for over 10 years. I’ve got lots of “in the trenches” experience in the dental lab. I enjoy helping others, and I never stop learning. Let’s grow together!