Eccentric Turning Setup for 3 Jaws Chuck

**LMMasterMariner** · May 1, 2019, 08:24 AM

Safe and simple. Much safer than putting various (potentially flying) objects under the jaw.
Shims made from 1 mm thick 316ss plates.

You can use as many shims as needed. Mathematics is simple, but you can also learn from trials and errors like I did.

Cheers
LMMasterMariner

**mklotz** · May 1, 2019, 10:02 AM

The mathematics (which you don't seem to describe) may be simple if you're using TLAR standards but they can become complicated if trying to compute the packing size accurately...

Actually, a much better approach is the tube method...

Programs to do the associated math for both these methods are available on my page in the ECCENT archive.

Better yet, do it right and mount the 4jaw which was designed for this sort of work.

**LMMasterMariner** · May 1, 2019, 01:30 PM

Originally Posted by mklotz

The mathematics (which you don't seem to describe) may be simple if you're using TLAR standards but they can become complicated if trying to compute the packing size accurately...

Actually, a much better approach is the tube method...

Programs to do the associated math for both these methods are available on my page in the ECCENT archive.

Better yet, do it right and mount the 4jaw which was designed for this sort of work.

You are right. Four jaws chuck should be used for this job. I have it but many people don't.
Also, title of this post is Eccentric Turning Setup for 3 Jaws Chuck.
Don't know if your calculations are based on arrow point like in your sketches
or calculations are based on true geometry of the jaws.
I am using graphic method for rough calculations of packing size.

**DIYer** · May 1, 2019, 02:12 PM

Thanks LMMasterMariner! We've added your Eccentric Turning Setup to our Machining category,
as well as to your builder page: LMMasterMariner's Homemade Tools. Your receipt:

Eccentric Turning Setup by LMMasterMariner

tags: chuck, adjustable eccentric

**bruce.desertrat** · May 1, 2019, 04:37 PM

Thank you both for this! In my stack of projects is a need to machine a small offset shaft; and yes, all I have is a 3-jaw...

**tooly** · May 3, 2019, 10:37 PM

Originally Posted by LMMasterMariner

You are right. Four jaws chuck should be used for this job. I have it but many people don't.
Also, title of this post is Eccentric Turning Setup for 3 Jaws Chuck.
Don't know if your calculations are based on arrow point like in your sketches
or calculations are based on true geometry of the jaws.
I am using graphic method for rough calculations of packing size.

I like the graphics method better, the maths may be correct but have not enough time to read it let alone calculate it.