[viroy]

I am going to replace my 3-jaw chuck with a 4-jaw on my 4th axis cnc.
It does not turn fast, max rotational speed is probably 120rpm at best.
I cut both square and round stock... wood, plexi, plastic, aluminum, brass and copper.
I have searched and searched but cannot figure out what brand my current 3-jaw chuck is:
Attachment 493766

I was hoping whatever company this is, has a 4-jaw model that fits the same bolt pattern of the 3-jaw.
Attachment 493768


But, if I cannot figure that out or there are no matching bolt pattern 4-jaw chucks, I have found two on ebay that look good.
I only have 3.25" between center of chuck to the base plate... so a 6" jaw would crash if the jaws ever extend past the chuck diameter.
I will just have to mill an adapter plate myself since I also havent been able to find a 1" keyed shaft matching a new chucks bolt pattern.
This one is cost effective:
https://www.ebay.com/itm/123457506296

This one sounds like better quality:
https://www.ebay.com/itm/330720133144

So is the second one worth paying almost twice as much for?
I'm curious if the 'self centering' only works with a higher RPM?
I would like your guys input, maybe even a better option available?

[metalmayhem]

the second chuck looks better made and though shars sells chinese products they are known to sell decent stuff . Regardless they are both cheap compared to high quality chucks . Personally I'd go with a 4 jaw that has independent jaws and not self centering .
The rpm rating is irrelevant when being used on a rotary . Thats more of a balancing thing for high rpm work which doesn't apply in this situation

[viroy]

I bought the shars, just arrived, looks good except for an error on the back plate... almost looks like a machine crash
Fits the 1.5" square stock with plenty of base clearance and good clamping power.