Thread: Which Chuck

Went and bought a dial micrometer w/mag base today and took some measurements on the Super Nova chuck.

Using the standard jaws that come with the chuck, I used two different size steel machined discs to take the measurements. I also measured along the body of the chuck itself.

I used jaw #1 as the reference point at which the dial face was zeroed out.

Here are the results measured from the body of the chuck going from jaw position 1 through 4 in order.

Here are the results measured from the jaw surface going from jaw position 1 through 4 in order using disc A held in jaws.

<!-- message --> Here are the results measured from the jaw surface going from jaw position 1 through 4 in order using disc B held in jaws.

The readings I got are not very encouraging. The body readings should have stayed at zero but didn't.

Steel disc A and B showed a lot of variation...most disturbing.

No wonder that the center of reverse chucked bowls did not run true

Ed, the worst case looks to be photo 3 - disk A. It is a whopping 0.0055" out, about the thickness of a coarse human hair. The fact that "runout" varied with different jaw sets could point to variations in machining of the jaws. Photos of where the stylus of the dial gauge was contacting would be helpful in diagnosis.
Cheers
GJ

Oops, sorry, reread your post same jaws different disk. The differences are still negligible, but it would be handy to see exactly what you were measuring.

Ed similar reading on mine but nothing over .003/4 you seem to have a couple of readings at - .00? if thats the case your going from a + to a minus run out

The disc's in the jaws are they true??

have you trued the jaws up first loosened them off then tightened the chuck up then retightened the jaws so that each edge of the jaw is true and join is true

I forgot to do this once when changing jaws almost .5mm out one side.

Now can someone explain what the 2nd screw thingy is on Ed's dial gauge mine has one also and for the life of me I can't recall or seem to find what it does????

Edited.. Ed I haven't done it yet but intend to remove the adaptor nut and check run out on it.
then as I have a pre-chinese chuck and adaptor do the swap and see what I get then.
Especially after speaking to President of Ornamental Turners finding out 2 other members have already had to return chucks and adaptors to Trend / Carba-tec with still no resolve.

Maybe we should get Funkyhicken to start machining top Aussie made adaptors

Whellin, one of those screws controls the sprung arm and contact point in or out.
The second loosens the outer dial allowing the pin to be zeroed out.

Originally Posted by Grumpy John

Ed, the worst case looks to be photo 3 - disk A. It is a whopping 0.0055" out, about the thickness of a coarse human hair. The fact that "runout" varied with different jaw sets could point to variations in machining of the jaws. Photos of where the stylus of the dial gauge was contacting would be helpful in diagnosis.
Cheers
GJ

Oops, sorry, reread your post same jaws different disk. The differences are still negligible, but it would be handy to see exactly what you were measuring.

OK John...heres the setup pic showing the contact point.

Ed good shot of set up

how much play is there in the jaw slides I know this can vary from chuck to chuck thats why I did my test with the jaws centred and closed

Edit
sorry Ed forgot you had the disc in there

Originally Posted by wheelinround

Ed good shot of set up

how much play is there in the jaw slides I know this can vary from chuck to chuck thats why I did my test with the jaws centred and closed

Edit
sorry Ed forgot you had the disc in there

...there is a ton of front/back play in the slides when there is nothing to bear against, thats why the use of machined steel discs

Ed, try checking the runout of the piece in the jaws not the outer diameter of the jaws. Although the outer diameter should run true that may not be the case. After all it is the runout of the job being held that you are trying to check, not the outer diameter of the jaws which after all is irrelevant.

Originally Posted by Grumpy John

Ed, try checking the runout of the piece in the jaws not the outer diameter of the jaws. Although the outer diameter should run true that may not be the case. After all it is the runout of the job being held that you are trying to check, not the outer diameter of the jaws which after all is irrelevant.

You are probably right GJ, given your background.

My only question is why don't turners spend the extra dollars and get Vicmarc chucks? They make next-to-useless rests IMHO but their chucks and jaws (some some exceptions) are great.

Jeff

Teknatool was as good as Vicmarc; I'm more than happy with my chucks.

It's only over the last few years that their standards have slipped so badly...

I would be interested in the runout with the chuck mounted on the lathe (with no jaws mounted on it) and the measurement taken on the face at the four points that the jaws mount/locate aganst.

This shows the runout of the chuck without jaws and eliminates any dodgy jaw manufacturing.

I haven't bothered to work it out but 5 thou at that distance what would it be on the outside of a 500mm diameter platter. (enough to make you redo the outside again when you chuck it to do the front. (APITA)

Cheers