Pm1127vf-lb New Chuck Or Back Plate

L

lpeedin

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Apr 22, 2014
Messages
479
Hi guys. As many of you know I am the proud owner for almost a year now of a PM1127VF-LB lathe (and recently a PM727 mill). I don't really use my 3 jaw chuck and one of the reasons why is that the run-out isn't the greatest. It varies with each mounting between .005-.010" run-out. I made sure to reinstall it with the witness marks lined up as it came from the factory. Since then I have rotated the chuck through a full rotation of mounting on the spindle as well as removed the back plate and re-mounted that to each different orientation. The results have been essentially the same no matter the mounting position.

With that said, I would like to try a new scroll type chuck or possibly to even try to make a new back plate. The problem that I am running into is that this lathe doesn't have a standard type of spindle nose such as a D1-3, D1-4, etc. Does anybody have an idea of what kind of new backplate I would need? I see places that sell semi-machined back plates, but, I can't seem to figure out what I would need. I assume I would need to drill and tap mounting bolts so that is not an issue.

With that, has anybody ever purchased new jaws for their PM1127VF-LB factory chuck? I don't have a set up to grind the jaws, so I had thought about buying new jaws if possible. Also, maybe even one of those six-jaw chucks?

Let me know if you have any information that may help.

Thanks,

Chad
 
Hello,

Sounds like its the backplate to spindle nose as your thinking, you can check the chuck for repeatability by marking a dot with a felt tip on the chuck and a round bar (a dowel pin is a fairly good thing to use if you have a long one) mark the chuck and bar for where they are when you first put it in, then look at the runout with a dial indicator, mark the high and low points on the circle and write down the numbers.

Remove the dowel (round bar) from the chuck and losen the chuck a little more then put it back in the same spot so the felt tip marks are lines up.

Re do the high / low spot check and write down numbers again.

Do that a few times should give you a good indication of the ability of the chuck to repeat.

You can check the 3 jaw to spindle in a similar way (just more booring if you have to bolt it down) check the high / low of the chuck body and make a note then take it off and put it back on then re mesure.

This should help to tell if it's worth re making the backing plate or if the runout is from the chuck itself.

Stuart
 
Have you taken it all the way apart and cleaned the scroll and teeth on the jaws?

We have a chuck like that, one of those with the cam lock that locks on 3 pins on the back of the chuck, correct? I was told it was taken apart at least twice by someone I was told was competent and it still runs out about .005. I haven't taken a shot at it yet but if when I do and it still runs out I may try another set of jaws....or encourage them to purchase another one, maybe a buck. It's a chinese chuck, I have my bias on it's quality.
 
for reference, this is what Bison (pretty decent chucks) considers acceptable run-out on 3 jaw chucks.
bison.jpg
 
Before attempting to true the mounting plate as on page 20 in the manual, I would check the hub and face of the back plate for runout. If there is no runout seen there, any attempt to improve chuck runout by refacing will be of no use. The runout then would originate within the chuck itself.

Bob
 
Tom,

There is no twist lock, it is a direct mount with three bolts. I will give the whole thing a once over this weekend. I love improving things rather than buying new things.
 
You must log in or register to reply here.
Back
Top