Mine works fine, but there isn't a lot of surface area on a small endmill which is why it should be placed on the collet. I can testify to the strength of the magnet -- when on the collet -- and you forget to take it off because you got distracted and you turned on the router. Works fine now though.
The video on the OpenBuilds page for the XYZ probe needs to be changed. It shows putting it on the bit
Well not really. The ideal place is on the endmill (shorter conduction path) the collet trick is for the times where you can't get a good grip (because the collet touches the bit, and is plain steel, whereas some endmills may be more silicon carbide than ferrous metal) - as you continue with the hobby learning curve, you'll learn docs and videos are to get you started, but nothing is ever set in stone
