I use a 50mm carbide-tipped cutter in my HY spindle. I would say that I get away with it rather than it's ideal. Runs at 7K, which is about as slow as my spindle will run and still give any torque. Only used for surfacing a spoil board and with no more than 0.5mm depth in ply or mdf. That was a cheap eBay buy, but it's ok for the job.