Is 8/1000 too much runout on a faceplate?

[Jesse Tutterrow]

I just bought a new steel 6" faceplate. It screws onto my Grizzly G0766 (powermatic clone) lathe fine all the way up to the flat area at the back of the spindle. Using magnetic base and dial indicator I get 8/1000 runout at the outside edge of the faceplate. This is runout that is not caused by the spindle. Is this too much? If so I want to return it during the 30 day return period. I did clean the spindle threads and faceplate with lacquer thinner first to remove dirt and machine oil.

 

[Dennis J Gooding]

Jesse, I can't think of a woodturning application where that small runout would not be negligible. Typically, the mating surface of the wood that is to be mounted to the faceplate is not flat to that accuracy nor aligned to the desired grain orientation to anywhere near that accuracy.

For example, suppose you rough turned a 6-inch deep bowl between centers, turned a perfectly flat surface on the base and mounted your faceplate perfectly centered on the center hole. If you mounted the ensemble on the lathe and brought up the perfectly centered tailstock, the tailstock center point would appear to be almost perfectly centered on the divot from the roughing phase. Actually, it would be off by about 1/16 of the width of a 1/8-inch divot.

 

[Mike Johnson]

Once your work piece is mounted to the face plate and the face plate is secured to the head-stock spindle, your work piece will be turned between the centers of the lathe and normally be parted off which your 8/1000 will not have any affect on the turned piece.

If you were turning a metal piece on a metal lathe with a finished surface mounted to the face plate, the 8/1000 would be an issue based on the tolerance allowed for the fit and purpose of the part being turned. The 8/1000 would multiply the error the longer the length of the turned work piece which would be noticeable.

 

[hockenbery]

Runout on the outer rim of the faceplate Only affects the balance of the spinning work. That small runout shouldn’t add a noticeable vibration.

Easy to check - run the lathe at fast speed with and without the faceplate. dought you can see or feel a difference.

The turned surface will be true about the center of rotation of the faceplate not related to the outer rim.

 

[Jesse Tutterrow]

Thanks. I learned a lot from my uncle who was a machinist / tool & die maker. So I have a tendency to want a tolerance of less than a 1/1000. I realise woodworking is different but that is the instinct built into me.

 

[Glenn Lefley]

8/1000 is too much. I pretty sure vicmarc tolerances are 1/1000.
You could not turn a pen to fit nice with those tolerances.
But I suppose if it’d centred properly and it's just outside might only be a vibration problem. I know I would complain.

 

[Richard Coers]

No idea what faceplate you have, so are you measuring runout on a painted surface, or raw steel? Do you see any balance holes drilled in it? If it's balanced, .008" is no issue. What is the runout on the face you will be using? With a gentle hand, and slow lathe speed, you could easily improve that runout with a file.

 

[John Jordan]

It doesn't matter, the piece will spin on a single axis and will be round regardless of the runout.

John

 

[Bill Boehme]

If it bothers you then it is too much runout, but otherwise it should be OK for most purposes. For what it's worth I have used M2 HSS scrapers to true up a steel faceplate, but there is a "gotcha". Truing up just the front face will unbalance the faceplate. A faceplate needs to be flat and that is not a trivial task when you're talking about hand turning steel.

 

[stu senator]

Is this axial or radial runout. It was not clear from the initial post. That could make a difference in all the answers.
Stu

 

[RichColvin]

It doesn't matter, the piece will spin on a single axis and will be round regardless of the runout.

John

John is right. Runout only matters :

1. If you mount a piece to this faceplate, having started it on another holding mechanism, or
2. If the runout causes too much vibration.

Otherwise, I’d ignore it as others have noted.
Kind regards,
Rich