Parting Tool Mishap

Sometimes you know better, … but you do it anyway. And you get some education in a hurry.

This is my most memorable mishap with a parting tool. Overall it didn’t amount to much. Only my pride was injured and the workpiece didn’t suffer significant damage. It was a cheap lesson.

I needed an end-grain blank about 3” in diameter to make a part for a light fixture. So I decided the quickest way to get it was to part it off from a spindle blank. Simple enough.

After mounting the blank in a scroll chuck, I used the parting tool to initiate the cut. The cut was wide for about one-third of the diameter because I was forming a tenon at the same time.

Then all that remained was to make a narrow cut the rest of the way through to part off the blank. At first, all went well. The tool was cutting like a knife through butter so I didn’t bother to widen the cut to give clearance for the parting tool. I pushed on.

That was my mistake. I could feel some friction on the tool but I thought I could control it. I was almost through so I gave it a bit of a nudge to finish the cut. And then – Bang!

The friction pulled the tip of the tool downward and deeper into the cut. The force was so great that it pulled the tool across the tool rest until the ferrule hit the spinning blank. It dug in and stopped the spindle. This caused the drive belt to slip and make this horrible squeaking sound that I’ve learned not to like.

I hit the big red turn-it-off-quickly switch, and the show was over. I found the tool wedged so tightly in the piece that it was actually difficult to remove. There was no way that a person could have held it and kept it under control.

To wit:

1. Always widen the cut to give clearance for a parting tool.

2. Don’t over extend the reach of a parting tool. When it’s deep in a cut you cannot see exactly what is happening, and you have less control. Use a hand saw to finish the parting off.

3. For normal light turning, let the drive belt on your lathe run fairly loose so that if you get a catch or have a mishap, the belt will slip.

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