Reply by Dan Krager

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Posted on Supershop owners

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Dan Krager

4461 posts in 2838 days

#1 posted 07-23-2019 03:48 PM

The centering cone is a feature of all tooling that must run concentric to a center. For chucks, it is most often a tiny shoulder that looks like a casual chamfer, maybe up to 1/8” wide most often at the largest diameter of the mating surfaces. When the threads pull the tool up tight, the chamfer forces the tool to “center up”. The action is similar to a MT “setting up” or a collet retracting into it’s cone forcing it and the captured work piece to center up.

Before I learned about this feature many years ago, I just assumed that the threads would do the job, but if one is interested in close and consistent tolerance, threads just won’t cut it. The moderns ISO standard for threads truncates the peak of the thread and the root of the thread. When mated, the peak does not meet the root. This means that the side wall of the thread can push the tooling off center at will. There has always been “slop” allowed for threads because they have to spin, and because of the pitch of the thread and any external forces, the mating can and most likely will go off center unless there is a centering feature involved.

That very feature is one of the things Tony Fox paid attention to when he designed the Supershop. As an engineer working for Shopsmith, he understood that the Shopsmith was inherently not accurate enough not strong enough for metal working. It’s plenty good for woodworking, and has served many very well. I used a Shopsmith to get my woodworking to a commercial level. So when the Supershop came along, well, the rest is history. Tony wanted to capture both the hobbyist woodworker AND metal worker, and that was the rub that separated him from Shopsmith. Tony took me to an auto repair shop using his machine, an off the shelf Supershop, to mill motor heads. Impressed, I was.


-- Dan Krager, Olney IL All my life I've wanted to be someone. I see now I should have been more specific.

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