As you are breaking so many you may be able to answer this - are the bits breaking when you plunge into the wood or as its cutting along a length?

The reason I ask is that the cutter does not have a cutting edge all the way along the bottom edge, so if you are plunging vertically into the wood as opposed to a ramp effect you may be putting loads of force onto the cutter! anyway that's my experience with that type of cutter.


Earle