TIP - How to check for router bit slippage

Checking for Router Bit Slippage
Are you sure your router bit isn't slipping during use? A slipping bit is an accident waiting to happen. This simple tip will help determine if your router's collet is firmly gripping the router bit.
To determine if your router bits are slipping, install a bit in the router and mark a line with a pen on both the shank of the bit and the collet. Next, make a few cuts with the router and check the position of the two lines. They should be perfectly aligned. If the lines have shifted the collet is slipping.
Remove the bit and clean out any sawdust, pitch, or other contaminants from the collet. Use a fine bristled brass brush to clean the collet.
Reinstall the bit and repeat the test. If the marks shift again you should replace the collet.