I attempted to make a duplicator similar to yours and I am having a big problem with tearout. I know it is the grind on the bit because I tried the same bit in the tool holder with the same results(it's an older logan metal lathe). I tried different types of wood and it tears everything, even maple which I had the best finishes with in the past. I've turned wood on this machine before, but I can't find the bit I used and I can't remember how I ground the bit to have it work right in the first place. What's the trick to this? I tried a square bit ground to a 60 deg. point with the nose radiused slightly, a thread cutting bit, and a radiused 90 deg. bit. I tried cutting on center, above center, and below all to no avail except above seemed to be the smoothest although I could only cut .020" at a pass and this machine can do brass at that depth. I even played around with the top and side angles and not much difference. Can you suggest anything for me to try? I know it shouldn't tear the wood up this much and I'm about at my wit's end with this.
