Things that can go wrong
This whole process isn't exactly simple. Things often go wrong when we're starting out. Start your troubleshooting my looking the the list of variables below. Then check out the questions and answers on the FAQ page. If you get stuck, contact us for help.
- Roundness of your balls - If the balls aren't round, a few things will happen. First, the hollowing tool will bounce around on the surface. Second, the chase being cut will be wide and it's very likely that you'll get a catch.
- Ball moving in the chuck - If your hemispherical chuck isn't contacting the ball well, things can move. That said, you shouldn't have to crank down on the ball too hard or you'll crack it as you progress.
- Cutter profiles - I had a lot of catches early on. I exploded ball after ball. Finally, I really looked closely at my cutters and realized they weren't ground to a proper profile.
- Sharpness of the cutters - The tip of the cutters need to be sharp. And, that should be the only part of the cutter touching the wood. I sharpen mine about every 6 to 9 holes without removing them from the holder.
- Flatness of the tool rest - If the height of the cutter changes as you move the tool across the tool rest, you'll have a bit of a problem.
- Stability of the tool rest - Make sure the tool rest is held very tightly in the banjo.
- Cutter height - Make sure that the top of the cutter is exactly at lathe center height.
- Proper guiding of the cutter - This shouldn't be a problem if your balls are round. Just make sure you the cutter's guide is registers well against the ball.
- Lathe speed - Use a speed that's comfortable for you, but you'll probably want to keep it under 1,000 RPMs. 400, 500 and 750 are commonly suggested. I use 500 and sometimes wish my lathe had a slower speed setting.
- Satellite holes - These can often be a problem when the inner balls are breaking apart. Try a ball without them, and then add them to one level of ball at a time as you find success.
- Wood choice - Use wood with a tight, closed grain. I found a lot of success starting out with basswood. It's fairly soft and cuts easily.