Truing up a sanding disc?

skou · Post by **skou** » Wed May 14, 2014 2:05 am

I've got an aluminum (ER) disc that is not quite flat. Is there an easy way to true it up? I'm thinking 2 different processes, one involves another disc mounted on a drill-chuck #2 Morse adapter in the tailstock. The other involves sanding it "flat," using sandpaper, and a sanding block and the ripfence on my ER table.

First scenario, mount the warped one on the spindle, and a decent disc on the adapter, in the tailstock, and GENTLY sand it flat. Second one would involve a piece of scrap lumber, that is known to be flat and square, and run it past the bad disc, again mounted on the spindle, and sand it smooth.

The second method scares me, because I could impart a cone shape to the warped disc.

Oh, we're talking about .005, or maybe .010 at most. Other issue, I don't have a tailstock adapter. (Yes, I know it is for mounting the drill-chuck, but it will mount ANYTHING that fits on the spindle.)

Any comments? Suggestions?

I've got 2 good discs, but wouldn't mind 3. (Can't have too many sanding discs!)

I've got some PSA 2 inch rolls of sandpaper, in 60, 80 and 120. I've also got 3, 11 inch aluminum sanding blocks ( Great Planes brand) that are made to hold this paper.

steve

rlkeeney · Post by **rlkeeney** » Wed May 14, 2014 5:54 am

I've never done this but I find the question interesting. I search a bit and found a lot of postings on the subject that gave me an idea. This is what I would do.

Mount a true running flat disk on the quill.

Square a jointed piece of wood with sand paper attached to the disk and clamp it to the table.

Mount the disk you want to true.

Use the quill to advance the disk until it lightly touches the sand paper. I think I would turn it by hand to start with.

You could do this with a saw blade or a face plate if you don't have a true running sanding disc.

I found people who claimed they had trued MDF disks using a sanding block by just sanding off the high spots until it was flat.

pieceseeker · Post by **pieceseeker** » Wed May 14, 2014 6:09 am

The easy way is to just pick up another SS that has a disc with it.

rlkeeney · Post by **rlkeeney** » Wed May 14, 2014 6:20 am

I wonder how much it would cost to have it done at a machine shop.

dusty · Post by **dusty** » Wed May 14, 2014 7:41 am

Hopefully you have done this already but the first step should be to make sure this is not the symptom of a runout problem.

JPG · Post by **JPG** » Wed May 14, 2014 7:01 pm

dusty wrote:Hopefully you have done this already but the first step should be to make sure this is not the symptom of a runout problem.

He has two disks that run true. He also has Model 10s.

He has not experienced 'run out'!:D

This may be a post of mine that Dusty takes as being snarkey. This was not intended to be critical of his runout post(His post was totally appropriate since runout could affect this).

My points were, Skou has two disks that appear flat. Model 10's have better quill runout than Mark x. Skou only has model 10s.

Yes I tend to leave out details at times. I assume others have read and retained previous posts both in the current thread and other threads.
My bad!

charlese · Post by **charlese** » Wed May 14, 2014 9:06 pm

Sorry! I don't understand the need to get a perfectly flat sanding disk

If used for sanding or sharpening it should perform nicely with a little warp in it. The most noticeable thin using a warped disk is a scrape- scrape rather than a steady S c r a p e . You might notice a bit more sandpaper wear on some parts of a disk, but no problem usually:)

If the sanding disk is used for some use where a flat surface is needed, that's another matter.

JPG · Post by **JPG** » Wed May 14, 2014 10:23 pm

charlese wrote:Sorry! I don't understand the need to get a perfectly flat sanding disk If used for sanding or sharpening it should perform nicely with a little warp in it. The most noticeable thin using a warped disk is a scrape- scrape rather than a steady S c r a p e . You might notice a bit more sandpaper wear on some parts of a disk, but no problem usually:)

If the sanding disk is used for some use where a flat surface is needed, that's another matter.

Me too! I think a hook/loop disc would vary more than 5-10 thousands.

"Wild Bad Bob" · Post by **"Wild Bad Bob"** » Thu May 15, 2014 1:31 am

I machine wood, not cut it!!! A 64th is only .0156, if you need or want your wood working that close you better get machine tools, not tools for wood working. IMO

skou · Post by **skou** » Thu May 15, 2014 1:43 am

Yes, I've checked for runout, on the 2 good discs. (Well, WITH the 2 good discs.) Mounted them up, spun them by hand, and held a pencil against the edge of the face, off the edge of the table. Good line all around. Loosened up the setscrew at the spindle, turned it a few (90 or so) degrees, gently tightened, tried again, got same results. Did it a few times, with both discs.

With the known bad one, did the same process. High spots were in the same place, after turning and re (gently) tightening the setscrew.

I'm still thinking, mount up a good disc, and the warped one. Gently feed one into the other, and see what happens.

Does it matter, if I spin the good one, or spin the warped one?

I think the "warped" one may just be light corrosion, because it was darker there, before I cleaned off the adhesive, and there was nothing glued to the dark spots. Looks a bit rough, too.

Oh, for those of you, trying to remove "schmutz" (yes, it's a word, I just made it up) from an old disc, if acetone won't remove it, WD-40 will.

steve