Adjust-true chuck w. 3 adjusting screws

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Adjust-true chuck w. 3 adjusting screws

This topic has 10 replies, 6 voices, and was last updated 24 October 2017 at 16:19 by John Reese.

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23 October 2017 at 22:45 #25579
John Reese
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@johnreese12848
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23 October 2017 at 22:45 #323170
John Reese
Participant
@johnreese12848
Recently I acquired a Japanese 3 jaw adjust true chuck with 3 screws for adjusting concentricity. I have no difficulty dialing in work on a 4 jaw chuck. The 3 screw arrangement drives me nuts when I try to dial in work. Can anyone recommend a straightforward method for centering work with 3 screws?
23 October 2017 at 23:24 #323175
Neil Wyatt
Moderator
@neilwyatt
Yes, have you got two of the screws at 90-degrees to each other?

If so, loosen the other screw right off, adjust using the other two, then nip up the 'odd' screw.

If they are all at 120 degrees to each other, bad luck…
23 October 2017 at 23:30 #323176
Michael Gilligan
Participant
@michaelgilligan61133
Assuming that they are equispaced [and none of them is spring-loaded] …

Use the DTI to find the screw that needs to be backed-off most [to move the work towards you]

Slacken that screw, and tighten the other two equally.

Rotate the chuck, and repeat the process ad nauseam

… It's easier to do than to describe.

MichaelG.

.

Centering Microscope condensers is easier, because one of the three is spring-loaded.
23 October 2017 at 23:34 #323178
peak4
Participant
@peak4
Well explained on these to links for the Griptru.

**LINK**

**LINK**

Bill
23 October 2017 at 23:41 #323179
Michael Gilligan
Participant
@michaelgilligan61133
Is it this one, John ?

**LINK**

http://www.yuasa-intl.com/images/products/pdfs/pg86.pdf

MichaelG.

.

See also: http://www.yuasa-intl.com/products_indv.aspx?pid=36

Edited By Michael Gilligan on 23/10/2017 23:44:12
24 October 2017 at 01:17 #323183
John Reese
Participant
@johnreese12848
Niel, It has 3 screws.

Michael, It is the 6 1/2 size Yuasa. Thanks for the procedure, except for the ad nauseam part.

Peak4, Thank you for the info. My shuck uses setscrews instead of wedges but the procedure should be the same.
24 October 2017 at 02:07 #323184
Hopper
Participant
@hopper
I think I'd be adjusting the three-screw chuck once and leaving set at that, using the four jaw for any precision set ups as it's easier. Cuts out the ad nauseam.
24 October 2017 at 04:09 #323188
John Reese
Participant
@johnreese12848
Posted by Hopper on 24/10/2017 02:07:22:

I think I'd be adjusting the three-screw chuck once and leaving set at that, using the four jaw for any precision set ups as it's easier. Cuts out the ad nauseam.

It will not be quite that simple. I have backplates to mount it to either my lathe or my rotary table. Each time I change its location I will have to re-zero it.

I found on my other adjustable chucks I had to re-zero them each time I made a significant change in diameter of the part. I assume it is related to inaccuracy in the scroll.
24 October 2017 at 09:55 #323209
IanT
Participant
@iant
I have a (damaged) GripTru lurking somewhere but not been tempted to do anything (like repair it) over the years.

To my mind it's a production tool – you set it for a certain diameter work and then just keep repeating with the same size of material. So it's not really designed to be used for constantly changing work diameters, I also have three 4-jaws of various sizes and they get used all the time – much better for one-off work.

Just my two 'penneth John but good luck with the "ad nauseum"

Regards,

IanT

Edited By IanT on 24/10/2017 09:56:06
24 October 2017 at 16:19 #323284
John Reese
Participant
@johnreese12848
Granted, the GripTru and similar chucks are well suited for production. They are also great general purpose chucks. If you don't mind the runout typical in most 3 jaw chucks, don't adjust them. When you have a critical job that heeds to run true, then you adjust them. That is the way I use mine.
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