Turning Archive 2005
>I noticed that there seems to be a statistical correlation to my own experience. Having turned many hollowforms in my life, the only two places I have ever cut through a side have been the exact same place he did, and at the transition from the top curve to the side wall when undercutting.
I have gotten a lot better at avoiding this, although it is still something that my bad work habits can produce when I do not follow the proper procedure or take short cuts.
Here are the things I do that can greatly reduce this problem.
1.) Measure often with calipers, but do not rely on them as the only means of inspection.
2.) Clear out shavings frequently. As you get thinner and thinner, the shavings will wad up along the walls and can cause the piece to vibrate, which will cause the inner cuts to be uneven.
3.) Use a high powered flaslight to gauge relative thickness. Thin walls transmit light, thick spots do not. If you can see the interior, you will be able to change where you place the cutter, and take light passes with the tool in the appropriate spots.
4.) Best advice I can offer is to switch your cutting tool from a standard 1/4" cutter to a disk cutter with a larger surface. Since the cutting surface is much larger, they tend to cut slower. As an added bonus, they also even out any ridges and leave a much better interior surface.
Hasn't stopped me from ever doing it, but if I follow my own advice, I rarely lose a vessel. Now if I could just find a method for accurately measuring the bottoms between an 1/8" and 3/16"...