Disc Sander Runout

[Pat Moy]

I noticed the disc on my new Jet JDS-12B 12" disc sander was wobbling a bit. I measured runout near the rim of the disc, and found it to be around .015". The seller sent me a new disc, which measured .0075". Given the fact that the Jet 12" disc sander cost over twice as much as the Delta and Grizzly sanders, measuring .0075" runoff was a little disappointing.

Does anyone have an opinion on what's considered acceptable tolerance for a disc sander?

[Pete Bradley]

You're kidding, right? What problem is this runout causing for your sanding?

Seriously, if this is radial runout, it's meaningless. If it's axial, you could probably clean it up in place with a sanding block.

Pete

Pete

[Pat Moy]

Not sure I understand difference between axial and radial. Can you explain? Thanks.

BTW, I called Jet tech support to ask about the .015" runout. The tech said .015" was a bit excessive, but wasn't sure what acceptable tolerance was. Also, if you take a look at the reviews of the Delta 12" disc sander on Amazon. One of the big complains was excessive runout.

[Pete Bradley]

Radial would be measured on the edge of the spinning disk. Axial would be in/out movement of the face. What really counts is how it behaves in use. If it doesn't sand continuously (e.g. sand-sand-sand-sand instead of the correct saaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaand), complain, otherwise don't sweat it. Certainly if the runout affects actual use of a new machine, you shouldn't tolerate it.

Pete

[Pat Moy]

Thanks Pete. The runout I was measuring is axial. I probably should have written: "on the face of the disc near the rim" instead of just "near the rim" in my original post.

I have an unrelated question: there's no way to remove the sandpaper without destroying it. Do people change grits on these disc sanders? In order to reduce cost, seems like one should use the same sandpaper until it wears out?

[Jason Beam]

My disc sanders are used as mid-level shaping tools so I leave a fairly coarse grit on there till it dies - I think what I have on there right now is 100 grit. I asked around when I had the same question and most folks I spoke to had a similar strategy.

One guy went and bought a velcro pad and uses hook&loop backed paper but he uses it more for final sanding than I do. If i did that, none of my edges would be anywhere near crisp. He acknowledged that issue and told me he wants another disc without the softness. He likes the softness for some things, but said he'd like to have the hard surface pretty frequently.

[David DeCristoforo]

If the runout is in the disk itself, you can true that up on the machine with course emery cloth and a wood block (much in the same way you would true up a piece of stock on a lathe). If it's in the arbor of the machine itself, there is not much you can do about it except to complain to the manufacturer (unless of course, there is a provision for adjusting this... not likely on a "low end" machine). My disk sander is actually a faceplate and table jig set up on my lathe. It's very easy to true up the backing disk which is a wood disk attached to the cast iron faceplate.