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Cup chuck design

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I would like to make a cup chuck for my lathe with a 1x 8tpi head stock. I will be turning 1x 1 bass, which has a diameter of 1.414 inches diagonally across the corners. Will a 1.25 inch interior diameter be enough compression to hold the bass stock?
 

Bill Boehme

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I would like to make a cup chuck for my lathe with a 1x 8tpi head stock. I will be turning 1x 1 bass, which has a diameter of 1.414 inches diagonally across the corners. Will a 1.25 inch interior diameter be enough compression to hold the bass stock?

Perry, are you asking about something like this from Robust? It is basically what used to be called a dead center being brought back to life as a drive center. I guess that makes it an undead center. :eek: You can also get the bowl drive cup that threads onto the basic cup center. Oneway sells a similar cup drive that they call a safe drive.

I assume that you are asking about a cup drive for turning 1" X 1" spindle stock. If so, you don't need the bowl drive cup center.

Cup-and-Bowl-Drive.jpg
 
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I’m not sure what you are asking. I make and use a lot of cup chucks for turning spheres and others that are basis of vacuum chucks.

what are you turning?

I turn a lot of small ornaments from 1x1 kiln dried bass blanks that I buy in bulk. Very uniform in size. If I were able to just tap them into a cup chuck for holding, things would speed up. As it is now. putting them in a scroll chuck takes more time than necessary and I still get close to those whirling jaws with the tool and knuckles. These are rather plain as turnings go, there is little art to them, but the 4 different ones sell very well to folks down on the Chesapeake. All made from the same stock. I am just looking for a quicker easier way to mount the stock and perhaps safer too (without jaw protrusions to bump knuckles.) I am going to try a few things to see how it goes.
 

hockenbery

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Yes that would be quicker. You also need a way to get the waste out of the cup.

You might be able to use an expanding collet Chuck or a pin Chuck.
Alternative 1
My wife used to turn a lot of tops for demos at fairs and such and give them to the kids that watched,
She used an expanding collet Chuck on a Morse taper. The blanks were prepped with a 1/4” deep Forster bit drilled hole. Collet fits in the hole twist the blank to lock it. Turn the top twist to take off the waste.
A quick search found this one. It is too large for you you can probably find one 3/4” size. The other issue may be that basswood is really soft and may not hold well on this Chuck. My wife used maple most of the time.
https://www.amazon.com/PSI-CXC-Expanding-Collet-Spindles/dp/B0006OC3EG

Alternative 2
a pin Chuck would work nicely probably need to be at least 3/4” long more waste.
The pin Chuck is round pice with a flat side and small steel steel rod the diameter of the flat cut away.
The rod is placed in the flat. The predrilled blank is slid over twisting the blank rolls the rod across the flat and locks the piece for turning. Twisting the other way rolls the rod the other way unlocks the so that you can remove the piece and catch to rod 9 out of 10 times the missed catch is searching through the shavings. I have one an inch in diameter similar to this one. This one does not use a pin. The end piece is cam mounted so it locks.
The 1/2” should do the trick.
http://www.peterchild.co.uk/chucks/pinchuck.htm


Option 3
A friend of mine used a wooden Chuck to hold squares for turning resets. You might consider making something similar.
The way it was made - three 1x3/4 pieces screwed to plywood disc on a faceplate. These made 3:sides of a square that fit rosette stock just a tiny tiny bit loose.
The fourth side was a similar piece ripped at a 15 degree angle with a 45:degree cut.
This made a sliding taper that will hold the rosette. The outside part is screwed in so that the whole piece will be too tight. The sliding piece was an inch or so longer than screwed on piece.

Blank put in the Chuck sliding piece got a light mallet whack.
Rosette turned
Sliding piece gets a mallet whack on the
 
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hockenbery

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I turn a lot of small ornaments from 1x1 kiln dried bass blanks that I buy in bulk. If I were able to just tap them into a cup chuck for holding, things would speed up.
To turn tops, Alan Lacer takes the handle on his skew and whacks blanks that size into the morse taper in the spindle. Many foreign turners seen on Youtube also do this with larger cups. You'd have to then line up the blank with the tail center, but this method would be wicked fast.
 
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