Spindle runout

[Rick Beko]

I recently purchased a Rockwell 46-525 lathe. When I put a 3" face plate on it seems to run on center....but when I put a 6" faceplate or my G3 chuck there is a slight wobble.

What is the correct method to check for spindle runout and how much is reasonable? Using a dial gauge against the spindle thread I get up 0.01" but there is excess movement caused by the threads. Against the spindle nut I get 0.006" but now I am measure the nut imperfections. The most accurate seems to be the inside of the hollow spindle where it measures 0.004". The run out on the spindle inside the headstock housing is only 0.001".

The spindle nut does not seem to have any noticeable imperfections but it is well worn. I do not feel any play in the bearings but would replacing them help?

Thanks for any suggestions

[Dick Strauss]

Rick,
You need to check runout with nothing connected to the lathe (no chuck faceplate, etc). Having anything else in the chain can either make runout worse or correct it.

First, find a smooth spot after the drive shaft exits the headstock. There should be a shoulder on the threaded shaft as well that may be a good place to check. You'll want to check it from the side of the threaded shaft (perpendicular to the shaft and threads). The further out you get from the headstock (in the direction of the tailstock) the more amplified the runout will be. Woodturning runout of 0.010" isn't a serious issue IMHO even though it may a little annoying.

Make sure that all faceplates and chucks bottom out on the shoulder of the shaft beyond the threads. If not, they will never be run true since the threads really don't hold an accessory well enough.


I hope something here helps...

[Paul Heely]

One thing to check is that the back of the 6" faceplate and the back of the chuck are tightening up against the shoulder of the spindle and not tightening up because the spindle itself is bottoming out in whatever you are screwing on.

FWIW when I measured the run out on my lathe I measured against the spindle shoulder and inside the spindle opening.

--
Paul

[Jim Underwood]

I have to respectfully disagree that .010" runout isn't much in woodturning.

That's a lot in my opinion. If you ever turn spindles then less than half of that is too much, and enough to cause vibration and chatter that won't go away. I returned a high dollar tailstock center recently because it was .0025" offcenter, causing .005" runout.

I couldn't figure out why I was having so much trouble turning my small spindles that I'd turned so many of, and finally realized that it was the tailstock center. I swapped back to my cheap Jet center, and the problem went away. It might be a cheesy center, but at least it was true, and didn't introduce vibration.

It pays to have this stuff dead center with no runout.

[Paul Engle]

I agree with Jim W., it is very annoying and if you are paying for RO of less than .xxxxx you should get it. Inside the spindle where the taper is should be a good as the outside or better as this portion is ground where the threads on the spindle are are usually not ground but are cut to one of 7 different specs. as are the thrds of the face plate and the chucks insert. Hard to tell unless you check the ro on the face of the spindle ( shoulder) or between the bearing and the shoulder which may only be 1/2 " in distance but the ro should be in factory spec < .0025 "or less and there again hard to see any difference.

[Dick Strauss]

I have to respectfully disagree. I've have turned items between centers on a PM3520 that has very close to 0.010" of runout at the livecenter end without any issues whatsoever. Possibly there is a difference in our spindle turning techniques (?). Spur center to live center connections take up the slop and you just end up turning on a slightly slanted axis to the bed ways. The spindle will still end up round though the ends may not end up perfectly square (assuming they started off square). If you are using a chuck, you need to get the spindle centered on the tailstock before tightening the chuck, otherwise you'll have the issue you mention!

FYI-This is an older used Rockwell 12"/16" swing gap bed woodworking lathe, not a new high precision metal working lathe. He didn't buy a new lathe where he should expect <0.0025" runout. If I had paid top dollar for a new Oneway livecenter, I can understand not being satisfied with lots of runout. Used tools purchases always come with an element of risk!!!!

[Rick Beko]

It is an older tool buy my previous Rockwell lathe ran true with this chuck. Mind you the chuck adaptor was different

[Andrew Derhammer]

You may need to true up the shoulder behind the threads. This is what the chuck and faceplates, etc rest against, the threads do no provide the accuracy it's the shoulder that does this and it needs to seat perfectly to run true.

[Dick Strauss]

Rick,
I apologize...my previous note was mostly directed at Paul and Jim. There is nothing wrong with your decision to buy a used tool at all! Paul and Jim seem to be writing as if you had just spent $6k on a new Robust lathe and your new lathe needed to be returned to the manufacturer because of quality issues.

My spindle turning methods work with or without runout.

Please check both surfaces of the shoulder for runout and check to make sure your accessories are bottoming out on the shoulder. You may also try to re-seat the adapter to make sure that isn't the issue with your chuck.

FYI-Most cast faceplates have lots of runout unless they have been finish-machined

Let us know what you find out and we'll try to help!


Take care,
Dick

[Rick Beko]

I ordered a replacement spindle nut from Delta and it fixed the problem.

I purchased this lathe a few weeks ago. I dismantled the lathe, replaced the bearings and painted it machine gray. I just used Rustoleum paint and the colour was very close to original. The Reese drive was removed with the 5/8HP Leeson motor and I replaced it with a 3PH 1HP motor and variable speed drive. I also installed casters that have a levelling pad so there is no movement. I have spent a few minutes on it and I am really liking it :D