My router bit moves

[tbellemare]

You guys are brave!

Not many things scare me but loose router bits are terrifying.

The causes that I know of have already been mentioned:

• bit buried in collet;
• dirty collet;
• corroded collet;
• worn out collet.

Tom

 

[denovich]

William... My Hitachi collet has slipped more than once when using a 1/2" upcut spiral.  I haven't ruled out user error, but I was using a new router/collet, new bit, all were clean, and the bit was not buried.  I heard the sound of the bit change (and stupidly rationalized that away) but quickly noticed that my dado was getting deeper. 

 

[BarBuilder]

I had the same issue you describe - turned out that the bit was lifting/rising in the "quickchange" collet as the workpiece traveled across it. Tighten the collet nut and see what happens. (or do like I did and scrap the faulty quickchange collet.)