Turning Archive 2006

Subject:
NE Bowl Depth Gauge

Bill Grumbine (Kutztown PA)
>Greetings all

It has been a while since I posted any pictures, and I have a few today. Here is the first one. Many of you know I have published pictures in the past of a two pole depth gauge for finding the inside of a finished rim bowl relative to the outside. It is a great tool for avoiding funnel syndrome. However, it is useless when it comes to natural edged bowls. In anticipation of a soon to come endeavor, I have devised a direct read jig for measuring the inside of natural edged bowls relative to the outside with a high degree of accuracy. Others contributed to this process, most notably a gentleman who posts under the moniker Robohippy on usenet. I will not post his name here out of deference to his privacy. This jig took his suggestions to me a little further in that the user does not need to do any measuring or calculating. My apologies for the clutter in the picture, but I was not hauling the lathe out of the way to get a better background. I have to move it soon anyway, but not just yet.

This jig was put together out of scraps of plywood and a couple of dowels from the hardware store. It is composed of three movable dowels on a freestanding base. The lower arm is located at the center of the lathe. The upper arm is located about an inch or so above the largest diameter the lathe will swing, in this case 26" plus a little. Both arms move in and out, and are marked with a sophisticated indexing system (pencil line) for quick alignment. They are oriented so that the bottom of the vertical dowel intersects at a point closest to the vertical arm of the jig, allowing for it to contact the surface of most bowls without introducing any extra error. In other words, the bowl is curving away from it at the point where it is most important.

To use it, stick it in the bowl just like you see it in the picture. Make sure all the lines are lined up, and you will see the relative positions of the inside and outside of the bowl. As an added bonus, this jig will work on anything on the lathe with a hole in it as long as the dowel will fit inside.

I hope this helps some of you out. It sure did for me.

Bill

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