How To Tackle Loose Bits
We often hear complaints that they are unable to tighten bits sufficiently to stop them from slipping when they start to cut. More often than not, this problem arises when they use a step-down sleeve to reduce the diameter of the chuck so that they can use smaller bits.
Sometimes, the bits remain loose even when the collet is installed correctly, that is when the slot on the step-down sleeve is aligned with the slot on the collet itself.
Our solution to this problem comes in steps.
Check The Bit Diameter
The first step to take is to check the diameter of the bit itself. Unfortunately, not all bits are exactly the size they are marked. If the bit is too small the sleeve will not grip it.
A quick way to see if your bit is undersized is to look for signs of slippage on the inside of the sleeve. If the bit has been slipping, the inside of the sleeve will appear polished, and there may be marks indicating the rotation of the bit.
If you find this, the only solution is a new step-down sleeve. A slipping bit will change the inside diameter of the sleeve. This can happen even if a correctly sized bit is not tightened correctly and begins to slip. Make sure they are tight.
Check The Collet
The next step is to see if the collet itself is bottoming out before the taper on the outside has a chance to come in contact with the taper on the inside of the chuck. When tight the collet should never be bottoming out. Check to see if the collet is bottoming before it grips the shank of the bit.
First remove the collet and use an emery cloth to sand the bottom until it is smooth and clean. Then use a black felt marker to coat the bottom with ink.
Replace it in the chuck, install a router bit and tighten. Then loosen and remove the bit to see if the ink is smeared. If it is this indicates that it is touching the bottom.
Use a flat file on the bottom of the collet. Then repeat the inking process and check after installing, tightening and removing a bit. Usually, it does not take much.