Adjustable Spider/Chuck Stop

[Peter Neill]

Here's a handy little accessory for turning or facing thin parts on the lathe.

It's an adjustable chuck spider that fits over the jaws, and has a threaded spinner to space it the correct distance away from the chuck face. The idea of a spider is not new, but I've never seen one with a threaded adjuster.
The plug at the back end is a close fit - half a thou' undersize - on the bore of the chuck, and sits behind the jaws when they close, with the spider supported by a smaller diameter shaft. The spider is held on the threaded shaft by a countersunk cap screw loctited in place.

The second picture shows it in use gripping a washer that was originally 0.074" thick after it had 0.020" faced off it.

Peter

 

[Wannabe2]

Hi Peter,
I think you have just created more work for me. I like the idea.
I'm a little unclear from the pics which part moves on the thread. Does the spinner move up and down the threaded (stationary) rod and the head is fixed to the threaded rod with the cap screw and stays stationary?

 

[Holescreek]

Peter, good to run into you again! I was going to ask the same question but Wanabes question explained it all for me. Keep up the good work. -Mike

 

[Peter Neill]

Thanks for the nice comments Mike.
I've still got a long way to go to catch with your productivity on useful gadgets though. A version of your motorised spin indexer is on the project list somewhere, and I've also got some outline ideas for a rotary broach, but they're both some way off.

As regards the operation, here's another picture which may help.
The spider is fixed onto the end of the threaded shaft with a countersunk screw loctited in place, and the spinner is moved up and down on the threaded shaft to set the height. The threaded shaft was screwcut at 40 tpi to give fine adjustment. In use, it's offered up to the chuck with the spinner hard against the chuck face and the required depth/height checked, then the spinner is adjusted back or forth until correct, then the workpiece placed hard against the spider and the jaws tightened.

Peter

 

[gilessim]

Nice work there Peter!, but if I could go off topic just a tadge, I was given a tin of the same brand of blue that you have in the picture, is it supposed to dry? mine doesn't and it's a bit messy to use ,is there a secret to using it?, I've been putting it on with a rag,is that ok?

Giles

 

[Peter Neill]

Thanks Giles.
No, that Blue won't dry out, it is 'marking' blue or 'transfer' blue as opposed to 'marking out' blue.
It's used for finding an interference between 2 surfaces, you lightly coat one surface (flat, angle, rod, or whatever) and then bring this into contact with the mating surface, and the blue will transfer from one to the other where the parts touch.
In this way you can check where the high spots are between the parts and adjust as required. That reminds me, it's also called high-spot blue.

I put mine on with a rag or a stubbly small paintbrush, depending on how thick or thin I want the film of blue.

Peter

Edit: Edited to add that WD40 will remove it from fingers and work surfaces quite nicely.

 

[gilessim]

Thanks Peter,that did actually come to mind, now I know, I'm probably better off using the big blue felt tip I've used for ages for marking out but the micrometer blue will no doubt come in handy now I know what it's for!

Giles