Turning Archive 2006

Subject:
Getting drilled on the lathe

David Breth
>I had my first chance to use a jacobs chuck on the lathe. Don't know how I had the stones to keep trying after the mishap.

Basically, I was using an inappropriate drill bit, such that when it hit imperfection in the wood, or a certain amount of resistance, or whatever, it bit and held the wood, meaning that the bit was no longer "stationary", but being spun by the lathe because it was stuck in the wood. It got exciting very fast, as it always does with a lathe.

My thumb got smacked by the first revolution of the wheel (that lives on the tail stock, which I was using to move the bit into the wood). Fortunately, it didn't have full momentum at the time. I got away with effectively a slap on the proverbial wrist (thumb), and I'm lucky I didn't break it.

The revolutions were basically unscrewing the tailstock and stuck bit from the turning. So, at a high rate of speed, the tailstock housing was traveling away from the turning, and therefore creating more opportunity for wobble and explosions. I raced across the back of the lathe so I could reach over the (encased) motor to shut it off (ie., I did not reach over the work). I fully expected everything on the lathe - hardware and wood - to blow up all over me. Very scary moment. I was torn between hitting the deck and trying to shut it off. I made my choice, and that was that.

I did ultimately have success, however. When I reset everything, this time I held the jacobs chuck with my right hand while I turned the wheel with my left hand to drive the bit into the wood, and I advanced the bit very slowly. As it turned out, there was very little resistance this time, even with the wrong bit type. Previously, there was nothing to keep the jacobs chuck from spinning given basically any amount of resistance - the first time the bit hit something it didn't like, and it dug a little, the chuck moved with it, that allowed the bit to stay anchored, and that started the dominoes.

I'm doubtful that my "successful" method of holding the chuck was a good thing to do, which is part of the reason I'm writing this. First is to share a mishap, second is to understand how I should perform this operation.

Embarassing? You better believe it. But I'd rather bite the pride to learn how to do this and to help others avoid it.

I'll be lucky if I survive my learning curve...

David B.

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