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arbors

I'm now up to vol.3 of David Gingery's metal shop series, the one on how to make your own metal shaper. He has a few comments in two places about how to make your own arbors. The ones he's describing are about 6 inches long and his comments are not very detailed. For example, on p.13, he writes: "It is impossible to drill a precise center in each end of a shaft, so you must begin with over-size stock to make your arbors. The diameter will then be concentric with the centers, and you can do accurate work on anything that you mount on the arbors."

I think what he means is this: (1) You can't to take a cylindrical rod the size you want and expect to drill a dimple at each end accurately enough that when the rod is mounted on a lathe using the two dimples, the axis of rotation will coincide with the axis of the cylinder. (2) Therefore, you have to take a rod which is too big, do your best to drill the holes you want, and then use the holes you drilled to mount the rod on a lathe and turn the rod until you have it down to the desired diameter.

Is that what he means?

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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Reply to
Allan Adler
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Yes. That's exactly what he means. Paul K. Dickman

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Reply to
Paul K. Dickman

Yes, that's what he meant. You can actually do it without using oversized stock, but it requires a little knowledge and equipment. By dialing in the material and carefully drilling the center holes, you achieve the same results. Centers are best drilled concentric with one another, although reasonable results can be expected when drilling randomly. In all cases, it's important to have the faces parallel and the centers as near concentric as possible to guarantee you end up with cylindrical turns. Many argue it is not important. I know it is.

Harold

Reply to
Harold & Susan Vordos

Now now Harold, let's not forget that the best tolerance the average HSM'er cares about is maybe half a thou, and especially that we're talking Gingery here.

Tim

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Reply to
Tim Williams

Well since its a Gingery item, I would think plus or minus a 1/32" would be close enough!

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Reply to
Roy

I try to never work that closely. Wears out my Lufkin tape!

Harold

Reply to
Harold & Susan Vordos

Yes.

And to make a 'true' arbor, or remove and replace the arbor and have it STILL running true, it also assumes the lathe is trammed properly and both lathe centers are themselves true to the lathe's axis.

Dan Mitchell ==========

Allan Adler wrote:

Reply to
Daniel A. Mitchell

If your rod is of the correct diameter, or is oversized, but turned truly round, you can center drill and get it almost correct. Then you put the end of the rod in a center rest, and turn the taper part of the center drilled hole concentric. Accuracy obtained, with patience, approaches turning between centers.

Brownnsharp

Reply to
brownnsharp

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