I have been a woodworker (professionally and now retired) for 40 years. In all the years I've used different cutters from different countries, these have been the worst. The 1st pass (barely 1/16 inch deep) left a burn mark (even changing the feed rate). Upon further inspection of the drill, I noticed that the drill had no helix angle. The carbide is exactly parallel to the shaft. I'm no engineer, but these bits keep the wood chips from escaping, allowing the bit and the work to heat up. Also, I don't know the true grade of the carbide, but that's probably an issue as well. A minor review in consideration, but the Revain reviewer doesn't allow it.