Problem using a chuck

Hi,

I purchased a Oneway Talon Chuck. I turned a square 2” x 2” x 14” piece of hardwood into a cylinder. The cylinder diameter was the maximum possible with the piece of wood.

Problem: After one, sometimes two, passes the wood would be loose in the chuck. I would tighten the heck out of it, repeat the action, and get the same loose wood result.

I had previously turned a similar piece from the same piece of wood and had no problems. However, I was using a center drive with teeth instead of a chuck.

I could not feel any flex in the wood in either case. Of course being a newbe to turning there could have been flex I would not know it.

Where did I go wrong?

Thanks for your response in advance and

Enjoy,

Jim
 
Hi Jim,

I'm wondering if you are gripping the corners of the 2 x 2 stock with the chuck jaws? If so, the resistance that builds up as you turn can move the wood in the chuck to where the corners fall between the jaw plates and the wood comes loose. If this is the case, try holding the wood in the chuck with the corners between the jaw plates and that will give you two points of contact in each jaw and the corners held tightly between the jaws.

It's 6.24am here and my brain is still asleep so I am probably way off the mark.

Brendan
 
How are you gripping the square stock, Jim? The four corners of the square should be sticking out through the gaps between the four jaws, sort of like this:

Chuck Square Grip.jpg

Another approach would be to start out turning the piece between centers (with the spur drive) long enough to form a round tenon on the end of the piece of wood. Then you can grip it in the conventional way, like this:

Chuck Tenon Grip.jpg

When gripping a round tenon, it's important to not have the end of the tenon touching the bottom of the chuck. The piece should be resting on the shoulder of the tenon, as shown in the picture above.

Let us know if any of this doesn't make sense. ;)
 
Jim, are you sure your Tailstock is in alignment with the chuck spindle.

Tailstock mis-alignment has little or no effect on between centres turning unless excessive, but if out when the stock is held in the chuck jaws, causes the wood to flex as it rotates, this then has a tendency to crush and bruise the wood slackening the grip in the jaws.
 
Hi Chas,

The tailstock center and the drive center pin align within a tiny fraction of a millimeter. They were so close that I did not try to align them. The tailstock was well seated each time I retightened the chuck.

Thanks and enjoy,

Jim
 
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...I will go check. The wood may be touching the chuck body...

If you're chucking a piece of square stock, I believe it is advisable to have the piece "bottom out" on the chuck body. It's only when you're using a round tenon that you should rely on the shoulder of the tenon and keep the stock off the body of the chuck.

Another thought...is the piece truly square, or is it slightly rectangular?

I hope you can get it figured out.
 
Let's troubleshoot with another piece of wood, if we may... chuck up another blank (it can be really pretty short - maybe 2" or 3" long), and tighten the chuck just as you did this time.

Release the chuck, take the wood out, and examine the jaw marks on the workpiece. Look really closely, even take a photo if you need to - we want to memorize what the jaw marks look like.

Now chuck it back up again, tighten as before, and rough-turn it to a cylinder. When it's round, check it for looseness. If it's loose in the chuck, tighten it down again, then unchuck it for another examination.

Compare the jaw marks now with the jaw marks from the first tightening. If they're really similar - not vastly different - then the chuck is somehow loosening on you (oil in the scroll? Something binding in the chuck?).

If the second-time jaw marks are much deeper than the first-time jaw marks, then the wood is compressing under the pressure of the jaws and the stress of rough-turning. I suspect this is the case... especially if you're not using a live center to support the tailstock end.

-- Tim --
 
Thanks Tim,
I will try the short piece as you suggest.
I did have tailstock support on the piece I was turning.

Aside: Your avitar shows Gumby. Clocke was a patient of mine when I was in practice in Ontario, CA. He lived 7 miles away in Claremont, CA. I saw his original film he made to demo the Gumby concept. It was sheets, rods, spirals, etc. that changed in with the musical background. I don't know what they call it. However, there is a type of music that is VERY stimulating to a human and this is what Clocke used.

He showed the film to a group. After the short presentation everyone was really high...you would have thought they were on drugs.

Enjoy,

Jim
 
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Gumbasia

Hi,

Man did that url bring back memories. You really made my day. I have told my kids and grandkids about it. They had all watched the Gumby series on TV but had not seen Gumbasia. Now they can!

It was great to see it on the computer---However, in a theater, in gigantic size, is a hundred times better.

Thanks again and again,

Enjoy,

Jim
 
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