Pot chuck

[mklotz]

Machining the face of a thin disk can be a trial. Superglue or jeweler pitch chucks are fine for one-offs but for multiples a pot chuck can be an asset. Commercial 5C pot chucks are available but a hobbyist may not want to buy something he will only use very occasionally. It's a straightforward task to make your own as this example shows...

This one is made to be mounted in a 3jaw, 4jaw or collet chuck. The body is machined to shape with a 1/4" through hole. Three slits made with a slitting saw allow the hose clamp to tighten the three jaws down.

To use it you insert a 1/4" pin in the hole and clamp it using the hose clamp. The front of the chuck is then trepanned to the diameter of the workpiece and a depth sufficient to get a grip on it. Loosen the clamp, remove the pin, insert the workpiece and tighten the clamp to grip the workpiece. The whole assembly is then mounted in the chosen chuck on the lathe and the workpiece is machined.

[Frank S]

Extremely handy little tools, I used to have a set of 5c's from .300 through 1.750. Not cheap.
I like your's

[mklotz]

deleted post

[Frank S]

Hardinge Makes what is called a 5 c step chuck at least up to 6 inches in diameter
I got mine at a government auction out of Lockheed

[mklotz]

My mistake, Frank. I thought you were talking about a 1.75 5C collet, not a step chuck. Stupid of me since I actually have a large size step collet.

[Frank S]

Sorry Marv but I thought we were talking the pot chuck not a 5C collet. I think my collet set only went up to about 1.062 but I didn't buy a boxed set. To me the terms 5C step chucks and pot chucks are too similar in nature and as my terminology vocabulary continues to meld terms together I sometimes do not fully explain my thoughts

[DIYer]

Thanks mklotz! We've added your Pot Chuck to our Workholding category,
as well as to your builder page: mklotz's Homemade Tools. Your receipt:

Pot Chuck by mklotz

tags: chuck

[Bony]

Thanks Marv, can you post a photo of the chuck in use please and what's trepanning by another name?

[Ropetangler]

The whole assembly is then mounted in the chosen chuck on the lathe and the workpiece is machined.

If you were using a 3 jaw chuck to make your pot chuck, chuck runout can be eliminated by not removing the pot chuck from the 3 jaw once you have completed machining it. Just remove the pin and mount the workpiece. Tighten the clamp and you are good to go. If you do need to remove it, by making an index mark alongside the No.1 jaw before removing the pot chuck will allow you to replace the pot chuck with a minimum of runout by just aligning the index mark with No.1 jaw again. I know most will already know all this, but this post is for for the benefit of raw beginners. Thanks Marv for all your most generous input,
Rob

[mklotz]

Thanks Marv, can you post a photo of the chuck in use please and what's trepanning by another name?

The collet version of what we call a pot chuck is called a step chuck. Here's a video of one being used...

I know of no synonyms for "trepanning". It's the word that is used to describe that operation.