Chuck jaw truing

A

abunai

Forum Guest
Register Today
I have an old chuck that needs the jaws to be "trued".
I was looking at different ways to pre-load the jaws.
Looking through a surplus catalog, I saw something called a "Lovejoy Coupler"
lovejoy.jpg
Looks like it would work with a little modifications.
Has anyone tried to use this?????
 
that may be a good idea.
not to discourage you in any way, but,
a point to consider is that the scroll may be worn in different areas, thereby giving a variable grip that may translate to differing runout measurements on different OD's of material.

how much runout are you experiencing?
 
Problem I'm having is the jaws don't grip near the top.
Project I'm working on needs to clamp thin round tube, with a mandrel, at the top of the jaw.
I'm thinking the jaws are not parallel anymore.
It's an old chuck.
 
The jaws should be clamped down on something at the front of the jaws, not the back; if you do it at the back and the jaws are somewhat loose in the chuck body, you will end up with the same situation that you have now, maybe less, but the same. If your chuck has solid (not two piece) you can drill holes in the end face of the jaw with a carbide drill, insert pins into the holes and clamp down on a steel ring and reach through the hole in the ring to grind the ID of the jaws; if you have two piece jaws, short pieces of allen wrench can be cut and inserted into the allen bolts and likewise clamp down on a ring.
 
i was able to put a narrow ring at the rear of the jaws and take very light cuts with a dremel tool and diamond encrusted die grinder tool ,mounted in the toolpost.
it reduced my runout from .020" to .004" as indicated on a .500" endmill stub (it took forever to grind!).
i didn't check runout on different diameters, but i felt it was a dang good improvement and lived with it until i traded the lathe
 
A buddy Dave made these to clamp down on while leaving the jaws exposed. He lent them to me to do mine.
KIMG0027.jpg
There is a small lip at the ends of the radius that catches the jaws.
Ideally you should be clamping at the end of the jaws, but where these are your in front of the scroll so the jaws will tip out.
This chuck was worn at the ends of the jaws as you describe yours. After grinding the jaws gripped evenly and runout was improved.
Beter chucks have one pinion marked, that is the one used when they grind the jaws at the factory and should give the best runout when using it to tighten. Use it when you grind yours.
Wonder if the ends wear or do they get stretched from the force of material expanding as it heats when turning?

Greg
 
This is where I saw the idea.
By using the "lovejoy" it would save me the trouble of making one.
Drilling holes is a good idea. But with this, I could use it on other chucks and not have to go through the trouble drilling.
 
just curious, how strong does the "pre-load" spacer thing have to be? It would be quick work to make one on a 3D printer if it could be made from PLA (plastic).
 
Back
Top