how to mount an aluminum disk repeatedly in the center

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dansawyer

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I am machining aluminum disks to as tight a tolerance as I can. gt2 belts will be mounted inside out on the disks to be used as gear teeth.
My experience has shown that removing and remounting parts do not end up in the same place. I have heard the terms mandrel and arbor; I am not sure which is appropriate here. I would plan to make a mounting centering mechanism for my lathe. It has an MT3 center and a 3 jaw chuck.
What can I make to ensure increased accuracy when mounting these parts?
The blanks have nominal 1/2 inch center holes. They are between 3 and 6 inches in diameter and between 1/2 and 3/8 inch thick.
 
When remounting work the key is indexing it. Even if you use an arbor or a mandrel you will want the work to be indexed to the same position. Jaw in the same place as each time before. If you are removing the work from the workholder you need to make sure it goes back into the same position.

It helps to indicate the work even in a 3j so you get it right before you cut again.
 
It would be useful to know more about your disks. Thickness, diameter , center hole, etc.

If I were making disks without a center hole, I would cut them from cylindrical stock. The stock can be faced and turned to an accurate diameter and a disk parted off. The cylinder can be faced again and a second disk parted. The parted faces of the disks can be faced in a secondary operation.

If there is a center hole n the disk, the center hole can be bored in the disks and the disks mounted on a mandrel turned on the lathe. As long as the mandrel isn't removed from the lathe, concentricity will be maintained.
 
The blanks have nominal 1/2 inch center holes. They are between 3 and 6 inches in diameter and between 1/4 and 3/8 inch thick.
 
Turning on a mandrel between centers will give you excellent repeatability for most applications. Your situation could prove difficult however. 6" diameter 3/8 - 1/2 thick and a 1/2" bore is not going to give much engagement on the mandrel. If you could have a wider hub in the center it would be better.
 
I would build a stub arbor that has a large back support area. In other words as large diameter as practical. Since your minimum width is 1/4, then I would make the stub about 0.240 long. Drill & tap a 3/8-16 hole in the end of the stub and secure the plate to the stub arbor with a screw & washer. If needed, add a drive pin to the stub arbor and drill a matching hole in the plate.

Once the stub arbor is built, do not remove it from the chuck until all of the plates are complete. This insures that the concentricity is perfect.
 
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