9 October 2019
9 October 2019,

When you put your collets on your machine, do you really need to use a collet wrench? Can you hand tighten your collets or use a torque wrench instead? Beginning machinists often wonder if they really need to use a collet wrench. It’s always a good idea to tighten your collets using a collet wrench. A torque wrench might over tighten and fingertip tightening might leave it too loose.

R8 tool holder

History of the ER Collet

As far as machining goes, the ER collet is a Johnny Come-Lately. Fritz Weber, a toolmaker from Switzerland, created and patented the ER collet in 1972.  In Germany, this design was a DIN standard within 20 years. His company, Rigo-Fix, is still in business today. Their high-quality tool holding systems claim to provide the lowest total indicated runout (TIR) for ER collets (≤0.0002 inch) over the entire clamping range. With such TIR possible, it only makes sense to honor the design by tightening correctly.

Fingertip Collet Tightening

Your first instinct might be to fingertip tighten your collets. That’s not a good idea. It might not be tight enough to dampen vibrations. Without rigidity you may get chatter. Chatter is guaranteed to interfere with material removal. Not a good thing. Chatter destroys tools too. If ER collet chucks are relatively inexpensive, why would you risk letting it ruin expensive tooling? Don’t do it.

Another problem with fingertip tightening is slippage. If your endmill slips, the torque doesn’t fit. Apologies to the late Johnny Cochran. But the sentiment is close. If your endmill slips in the collet, the torque wasn’t right. Techniks has a great online torque chart for you to follow.

Use a collet wrench instead of fingertip tightening.

Torque Wrench Collet Tightening

On the other end of the spectrum is torque wrench tightening. Just the opposite of fingertip tightening but still delivers less than optimal results. Where fingertip tightening may leave collets too lose, its easy to torque down too tight. Get it too tight and you get runout and ruined collets. Collets may be cheap, but runout ruins your work. That’s not cheap, no matter what you are working on.

Sierra American collet wrench

Using a Collet Wrench

Yes, you do need to use a wrench to tighten your collets and the proper tool for the job is a collet wrench.  And the proper collet wrench is made by Sierra American Multi-Systems. Use it to insert collets into the nosepiece and know you are using just the right amount of torque.

Never lose your wrench again. The brightly colored high impact plastic is guaranteed to stand out.

Get your Sierra American collet wrench where you buy your CNC supplies and never suffer from incorrect torque again. Because yes, you do really do need to use a collet wrench if you want to reduce runout.




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