Misaligned chuck query!

[Richard Kennedy UK]

Hello and apologies for not being about more recently! I have been having a few issues with my new 3520b setup! At the moment I am having a few woes with the chuck and jaws I Have a VB which came with an axminster super precision chuck it worked absolutely great ran true with no issues however having replaced the backplate to suit the 3520b thread I cant get it to run true. Its not the lathe I am pretty sure about that the centres line up a dream and there is no movement in the spindle but when I use the screw chuck in the chuck jaws (which worked fine with the VB) I turn the outside of a bowl but when I reverse it onto the spigot the lip of the bowl won't run true. I used a pencil to highlight the high spot it affects about a quarter of the rim however when I loosen the bowl and give it a quarter turn and then tighten it up again the wobble stays in the same place. Could one of the jaws gone out of alignment? I have stripped it and cleaned it but the problem still persists any advice?

I can't afford a new chuck at the moment so I have to get it fixed most of my work is thin walled stuff and this wobble is ruining the wall thickness

Help!

[Nate Davey]

Several of us have had issues with the inserts to adapt our chucks to our spindle size. Not sure if you have one. The best thing I can recommend is a cheap dial indicator to see where the run out is.

[Allan Ferguson]

Check the to see if the spindle is interfering with the jaw, it may need a spacer behind the chuck. If the yaws don not close properly on the screw you could end up with miss alignment.

[Cathy Schaewe]

I had trouble with one of my inserts, too. I couldn't figure out what it was for the longest time, but it was because I was using the insert on two different chucks, and it just wasn't getting tightened down enough on the bigger one. I got another insert, really cranked it down, and that did the trick.

[Dan Hintz]

Definitely determine the location of the runout. A couple of months back Mike C. said the adapter (about 3" long) I gave him was crooked and added wobble... upon closer inspection, however, we noticed his main shaft was wobbling. You didn't notice the shaft wobble very much because it was so close to the motor shell, but once you added a 3" extension the wobble was more readily noticed as it was circumscribing a much larger circle. If he was able to stick with a chuck right off of th emain shaft, the wobble would likely be manageable, but the adapter killed it.

[James Combs]

I recall a post sometime back where several folks were having run-out problems with, I believe it was Nova chucks. They weren't seating completely on the spindle shoulder. Normally about an 1/8" of the un-threaded portion of the spindle will fit inside the chuck adapter. In the problem cases if memory serves me right the un-threaded portion of the spindle was a few thousandths larger then the hole in the adapter and would not allow the chuck to seat against the spindle shoulder. Perhaps your problem is similar.

I also recall some Nova chuck users having problems with third party spindle adapters, just another thought.

[Richard Kennedy UK]

Thanks everyone for your input I had a good look at the seating and the thread length and after much inspection I discovered a slight imperfection in the backplate which I have attacked with some fine grit removed and hey presto instant improvement! So thanks ever so much I now have a problem of removing one of the grub screws on one of the jaws it is stuck fast and I have almost ruined the head of the screw trying to get it out I fear it will have to be drilled out but I really don't want to damage the jaws or the chuck its attached to!

Thanks again

[John Keeton]

Richard, have you used penetrating oil on the offending screw? And, perhaps seating the allen wrench and tapping it with a hammer to unseat the screw?

[Dale Miner]

As John said, make sure the allen wrench seats completely, and also make sure that the allen wrench is not damaged or worn. The ball ended type allen wrenches are not a good choice for stubborn screws as there is not enough metal in engagement for high torque. A slight bit of wear on the wrench is enough to make the wrench slip. If there is wear on the wrench, try grinding an 1/8" or so off the end to get to an unworn area. Don't allow the wrench to get very hot while grinding to avoid losing temper in the metal. Something to try; Put a dusting of talcum powder in the socket of the screw head before inserting the wrench. The talcum helps add a bit of friction to the metal surfaces. Another trick; Lay the chuck on it's back supporting the body with pieces of wood, take a 1/4" hex head bolt and put the head of the 1/4' bolt on the head of the screw. Give the end of the bolt a light to medium tap with a hammer. The jolt of the tap will sometimes help loosen the screw. Another trick; lay the chuck on it's back, put a wrench in good shape in the socket on the screw head, put a small drop of CA in the socket in the screw head while the wrench is in the socket, and give it a shot of accelerator. Do not allow any of the CA to get out of the socket and into the joint between the underside of the screw head and the jaw. The CA will fill any gaps between the wrench and the socket and may help the wrench get a better purchase on the screw head.

[Richard Kennedy UK]

Thank you all again I can now confirm the screw is gone!!!! although I did end up drilling it out! I managed to round the socket bit of the screw so the allan key just turned anyway its out and I didn't damage the chuck or jaw so great! Thanks for all your help! I might actually get some turning done!!!