What Is the Proper Tightness for Collets on Router Bits and Bit Shanks?
posted on April 1, 2011 by Woodworker's Journal

Q: I have several routers with different type collets. How do I know how tight is tight enough to keep the router bit from slipping versus too tight which makes it hard to loosen when I need to remove the bit? Is there a “rule of thumb” to use to get it tight enough, but not too tight?

Router Collet Ensuring that router bits are securely tightened is important, but every collet is different, so how tight to make each one is an interesting question.

A: The method I favor is the one-handed squeeze. I slip the bit into the collet and twist the nut finger tight. After tightening more with the wrenches, I give it that final one-handed squeeze, as shown in the photo at right.

Reversing this procedure will usually free the bit. Engage the wrenches on the nut and spindle with their handles offset and squeeze them together to crack the nut.

The method doesn’t work with every router; some models only have one wrench, supplanting the second with a spindle lock. With these routers, you have to learn from experience how tight to make the nut.

Collet design greatly impacts this operation. The collet and socket are precisely scaled so that, when forced into the socket, the collet deforms around the bit shank to grip it tightly. The collet nut is what forces the collet into the socket, of course.

Twenty-five years ago, the typical collet was short and steeply tapered. Considerable force is needed to drive this collet deep enough for it — short as it is — to get a proper grip on a bit’s shank.

Nowadays, better routers have a longer collet with less taper, one that’s connected to the nut. It grips at least twice the length of shank that the old style collet does. The shallow taper requires more turns of the nut to seat it, but once seated, it won’t pop loose. In fact, you must drag it out of the socket by unthreading the nut.

If your router with the old style collet can’t get a sure grip on bit shanks, try replacing the collet. If that doesn’t eliminate the problem, I’d retire the router.

posted on April 1, 2011 by Woodworker's Journal
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- Orval - 08/07/2012
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