Jacobs Rubberflex chuck runout

[matthewsx]

Hi,

Quite a while back I was able to purchase a rubberflex 91-A6 in good condition. At the time I had a Bolton lathe with a Din spindle mount and I removed the threaded backing plate thinking I would adapt it to my funky spindle.

Well, that never happened and I put it back together but realized I didn't mark the orientation as it was when I got it.

Now I have a lathe with the right threaded spindle and have mounted it up. I'm getting about .003 runout with my trusty piece of drill rod I use for measuring such things.

My question is, am I in acceptable range or should I attempt to clock it in better? And, if so does anyone have tips for how to do it?

Thanks,

John

 

[matthewsx]

 

[pontiac428]

John, I think the Jacobs can do much better than .003 TIR. You should be seeing .001 or even less. Can you remove the retaining cap and collet and run your indicator over the taper inside? I think once you have the chuck centered on the spindle, your entire collection of collets will dial near-perfect, they are a low-runout fixture by design. I sure have been impressed with them. They're like a 1.5" minus 4-jaw for lazy people. Speaking for myself, of course.

 

[mmcmdl]

/\/\/\/\ A .001 or less is the norm for these flex collets . Dial the chuck itself in true and check for rough edges , rust etc on the tapered end of your collets if it still doesnt run true . These are nice tools that were expensive back in the days .

 

[matthewsx]

Thanks, thought it should be better. I probably messed it up when I took it apart.

 

[pontiac428]

Thanks, thought it should be better. I probably messed it up when I took it apart.

I doubt that, John- it's a concentric design with only one way to assemble it. Perhaps try a different rod and collet? Dave is right, the steel fingers can pick up gunk and oxidation. In fact, that gives me a good excuse to scotchbrite mine and dump them in the ultrasonic bath.

Also with collets in general, I snug them, loosen, then tighten to align the collet. Doing it in one shot violates my superstition.

 

[mmcmdl]

If I remember , don't these mount onto the spindle mount with a pair of pins ? I sold all of mine and CRS .

 

[pontiac428]

The collet cone might be pressed into the body with pins, since the cone transfers the driving force from the plate to the work.

 

[jetlag]

I've had good luck with that system in the past, I'd guess you can get it dialed in better. I'd agree to start with a different collet, see if the numbers are much different. Possible you have a worn collet.

 

[matthewsx]

I checked at the taper inside the chuck and it was the same. I’ll take it apart again and try rotating it 180* on the mount.

John