Sanding disks on a lathe

[Nick]

How do you mount the disk onto a lathe?

[JHowell]

Fanged Dypoes. Why do they alvays smeak in on uz? Hate it whed tat hapens.

Heh, heh, thought maybe you had put your tongue on it. What kind of disc? There are wood lathes that come with a sanding disc attachment on the off end, but those discs are, I think, pretty specific to those lathes. There are small sanding discs that have a stub for chucking in a drill; you could just chuck those in the 3-jaw. 3M (and similar) 6" disc systems (for auto bodywork) come with a short threaded stub -- you can either make a mandrel or run a couple of nuts onto the stub and chuck them up that way. Other sanding discs sold for use with body grinders have something like a 5/8" threaded hole -- you'd have to make a mandrel for that. Unless space is an issue, it's probably easier in the long run to get an arbor from Grizzly or put a mandrel on an electric motor and have a disc that's always set up, and for which you can run a good dust collection system, which is really the biggest issue.

Jack

[KurtHuhn]

The sanding disks backing pads I use come with a stub for chucking in a drill/drill press. Most do, actualy. There's ones available at Sears, but I thought they were rather low quality. There are also 7" and 9" DA backing pads, designed for electric and pneumatics DA sanders, of the type you would see in an auto-body shop. Those are, IMO, of generally higher quality. They seem to be less prone to runout and are less out of round. The only issue is that he stub is threaded instead of being a 1/4" unthreaded stub. However, you can easily chuck it in a drill just the same.

The best backing disc I've used to date is this one:
http://www.woodturnerscatalog.com/cgi-b ... y=415-0300
It's only 3 inches in diameter, but that's really all I need. I only use it for cleanup on a pipe rough shaped with a belt grinder. You could probably use it for all sanding, since you can get 3" discs in 600-grit and beyond.

[Tyler]

This depends upon your lathe, I'm sure, but for most, you need a Jacobs chuck with an appropriately sized morse taper to insert into the headstock spindle. For my Delta Midi, a #2 morse taper fits both the headstock and the tailstock, so I can switch the same jacobs chuck back and forth for head to tail for sanding/buffing and drilling respectively.

As Kurt points out, the back of the discs have a rod for chucking into a jacobs chuck, so you just insert the chuck, chuck the disc, and roll. JHowell mentions that someof these rods are threaded, but they still work. I would be very interested to learn how to consistently chuck these well. I have always had issue with runout because I couldn't chuck the threaded rods squarely. Is there a trick to this?

Tyler

[ToddJohnson]

I have always had issue with runout because I couldn't chuck the threaded rods squarely. Is there a trick to this?

Tyler

Yep. Use a *4* jaw chuck first of all. Chuck the disk up tightly in the headstock and spin it to see how true it's turning. Keep adjusting it until it turns as true as you can get it to turn. When you've got it aligned "properly" mark one of the jaws with a corresponding mark on the arbor/threaded rod. Now, get a really rough file, spin the disk at about 1400 rpm.'s and, holding the file at about a 45 degree angle, file the disk down until it's perfectly round and turns in a perfectly concentric manner to the arbor/threaded rod. If you use resin backed disks like I do, you can do the same basic thing with the actual disks each time you change them to make certain they're turning true.

Best,

Todd

[JHowell]

If you use resin backed disks like I do, you can do the same basic thing with the actual disks each time you change them to make certain they're turning true.

Todd, the discs you use have the stub? Would you mind elaborating on what sort of disc you use? You said fiber backed and resin backed -- are these a bonded wheel like cutoff discs, or backing plates with DA sheets? An auto body supply item?

Regarding chucking threaded rod, I'd still recommend spinning on some nuts, or, better yet, drilling/tapping a piece of rod stock to chuck in the lathe. The threaded rod presents so little bearing surface that it can spin in the chuck, which puts the disc back out of round.

Thanks,

Jack

[ToddJohnson]

If you use resin backed disks like I do, you can do the same basic thing with the actual disks each time you change them to make certain they're turning true.

Todd, the discs you use have the stub? Would you mind elaborating on what sort of disc you use? You said fiber backed and resin backed -- are these a bonded wheel like cutoff discs, or backing plates with DA sheets? An auto body supply item?

Jack, the backing plate has a stud which passes through the plate, is secured with a nut on both sides, and can be chucked up in the lathe. The actual sanding disks are resin backed 3M disks with a 3/4" hole. They are secured to the backing plate in the same manner with two nuts and two large washers. There is no adhesive bond to the backing plate because this causes too much friction and eventually burning. This is a setup I made myself, but you can probably do the same thing with a mandrel and an angle grinder backing plate.

Regarding chucking threaded rod, I'd still recommend spinning on some nuts, or, better yet, drilling/tapping a piece of rod stock to chuck in the lathe. The threaded rod presents so little bearing surface that it can spin in the chuck, which puts the disc back out of round.

Jack, this is the whole point of the threaded rod, the mark on one of the jaws of the chuck, etc. With as much force as I apply to the spinning disk, round stock in a 3 jaw chuck would itself spin. I use a 4 jaw chuck with threaded rod chucked up directly. If you want an exact alignment every time, heat the threaded rod with a torch until it's almost red hot. You should have already made some alignment marks with a pencil. Put it into the 4 jaw chuck and tighten the chuck with crushing force. Now, using a metal scribe, mark one jaw of the chuck with a corresponding mark on the mandrel. True up the disk with the method I laid out in the previous post. Now, nothing will "put the disk back out of round."

Todd

[Nick]

Kinda lost me there bud, but not having a lathe to look at doesn't help. Maybe I'll get it when I finally get my hands on one.