What is a Self-locking Stub Arbor?

[T Bredehoft]

I'm gonna take a guess at this.....

Its' for second operation on a production part. The part has a concentric bore which would be a very nice fit on the stub arbor.

The operator installs the stub arbor concentric in the lathe, with the loose pin in place. The operator then slides the work over the arbor and turns on the lathe. The pin wedges itself into the corner between the arbor and the work, spinning the work. The work is completed, the lathe stops and the operator twists the work top toward them, loosening the pin. They remove the work from the lathe, dig the pin out of the chips and repeat the procedure on the next piece.

And Bob's your uncle.

 

[Chips O'Toole]

That's what I thought when I saw it, but why would the pin lodge itself instead of rolling?

 

[BGHansen]

I found out a guy named Duclos made his own air spindle and wrote it up in Home Shop Machinist magazine, so I bought a back issue and looked at it. It looks like a surprisingly simple project, which suggests there are things about it I don't understand. The article appears in two issues, and I don't have the second part yet. Maybe that's where the fun starts.

As part of the process, he tells the reader to make a self-locking stub arbor. He gives no details at all, like every hobbyist is born knowing how to do this. I don't even know what a self-locking stub arbor is. I know what an arbor is, and I guess "stub" means it's short, but that's about it.

Can someone tell me what he's talking about? I'll upload a photo of a photo. Sorry about the quality.

View attachment 312116

Which issue are you missing? I have every issue starting from the first one in 1982 (or whatever year they started publication). Might be able to help you out with part 2 . . .

Bruce

 

[jmkasunich]

That's what I thought when I saw it, but why would the pin lodge itself instead of rolling?

Same reason morse tapers don't fall out. If the size of the pin and the size of the flat on the arbor are chosen properly, the angle between the flat and the point on the workpiece ID where the pin touches is very shallow and self-locking.

 

[Chips O'Toole]

Which issue are you missing? I have every issue starting from the first one in 1982 (or whatever year they started publication). Might be able to help you out with part 2 . . .

Bruce

Thanks, but I decided to spring for both issues. It's entertaining to look at these old magazines. It's surprising how little machine prices have gone up. It looks like lathes were more expensive in real money than they are today.

 

[Chips O'Toole]

Same reason morse tapers don't fall out. If the size of the pin and the size of the flat on the arbor are chosen properly, the angle between the flat and the point on the workpiece ID where the pin touches is very shallow and self-locking.

This is the kind of information I was looking for. Now to get specifics. Maybe I can find something in Machinery's Handbook.