12" PSA discs not sticking to Jet sander

[Mark W]

Ok, here we go. This is my first post on the rec, although I have been lurking for several years now. Usually any question I need answering I can easily find by dags, but this escapes me. I just received a Jet JDS-12B 12" disc sander for my birthday (Yes, I picked it out). UPS brought it today from Amazon, along with some extra discs from Grizzly (Woodstock Int. brand). Well, anyway, I cleaned the oils and cosmoline stuff off of the sander with denatured alcohol, taking extra care to get the disc itself clean. I peel the backing paper off of my first disc, taking care to get it aligned JUST right before I stick it on. (After all, I get only one shot at this, right?) As I press it carefully into place, it starts coming right back off when I release it! Ok, so I figure it's one of two things; either I didn't get the oils off the metal disc, or it's cheap glue from the aisian import sandpaper. So, I break out the laquer thinner and scrub the metal disc again. Well, just maybe I got a little more off, but I'm not really sure. Looks just as bone-dry as before. So, I try the same disc again and it falls right back off when I let go. Ok, so maybe I ruined the disc before, or maybe bad glue, so I try the disc that came with the sander. It's a 60 grit. (What's THAT for, shaping telephone poles?) Well, same results. The discs seem pretty sticky to me, I feel certain if I stuck them to any smooth surface I would have trouble getting them back off in one piece. On closer observation, I see the metal disc has small well-defined grooves in it, sort of like a record album, but coarser. Could this be part of the problem? Should this disc be really smooth? I'm more of a neander woodworker, and this is the first stationary sander I've ever owned, so am I missing something here?

Mark W

[Leon]

For a nice clean surface I like to use Acetone.

Old PSA paper does not like to stick well and Cold SPA paper does not like to stick well. Try heating the disk or pad and reapplying. Keep in mind also that PSA does not like to be restuck.

[Steve Knight]

O

I have had discs that don't stick either. if the paper backing does not stick well that's a good sign it won't stay on. want a few? (G)

" Eagles may soar, but weasels don't get sucked into jet engines"

[Lew Hodgett]

No, boat parts, beats the devil out of anything else for forming complex parts.

[J. Clarke]

I'm going to go through a sequence of more agressive cleanings here--you can go all the way through or stop when you get to "clean enough". This is based on years of experience in the aerospace industry and these are stages that are gone through to prepare metal surfaces for adhesive bonding in that industry.

First thing, get a roll of duct tape and use that to test--if duct tape won't stick then nothing will, and it's a lot cheaper than wrecking sanding disks. Also, use paper towels or _new_ cloth or something else you're _sure_ is clean for all cleaning steps--if unbeknownst to you there's a little grease on the rag you're using you'll never get the thing clean. Also use solvents from a new can and pour them into a container rather than holding the can upside down with the rag pressed against the spout--you can get contaminants in the solvent that way, and again if there's any grease dissolved in the solvent you'll never get the thing clean.

Next, pull the metal disk off and make sure that it didn't get installed with the "good" side in instead of out at the factory. If it's that simple you save a lot of work. While you have it off, soak it in a pan of MEK for an hour or so then wipe it down and go over it with alcohol afterwards. If the tape sticks, then put it back on with the "better" side out and try a sanding disk and you're done. If the tape doesn't stick then you need to get more agressive.

Next step is to get rid of those tool marks you noticed. Make up a straight sanding block wide enough to cover the width of the disk, turn on the sander, and sand the disk surface with increasingly fine grits of sandpaper until it's smooth and shiny. Wipe it off with MEK followed by alcohol. Again try the tape--if it sticks, try a disk, if it sticks well enough you're done.

If that doesn't work, then it's time to try to get the surface really clean. You need a test for cleanliness that is more precise than "will tape stick" and on smooth metal that test is called a "water break free surface". Pull the disk off the sander and throw it in the sink and scrub the Hell out of it with Comet or Dutch Cleanser or whatever is your favorite scouring powder--don't use BonAmi--don't know why but the specs always said specifically not to use it. "Old Dutch" if you can find it is the best. When you're done, rinse it off and see if there are any spots where water beads up or where there's a hole in the water film on the surface. If there are, scrub those spots some more until the water film after rinsing is continuous over the surface--that's a "water break free surface" and it's as clean as you're going to get without going to a chemical etch. Dry it thoroughly.

If the sandpaper won't stick to a water-break-free surface then you've got bad sandpaper.

If you can't get a water-break-free surface then there's some exotic contaminant on the disk that's going to take a chemical etch to remove--without knowing what the disk is made out of I can't tell you what to etch it with.

[Rumpty]

Gee I don't have this problem with my hook and loop sanders!

[George]

I thought those machined concentric circles were designed to keep the disc from sliding under mild prolonged pressure, and help with cooling. If so, removing them would make the disc hotter and facilitate glue creep.

I'd think twice about removing obvious machining, especially given the ease of just lapping the plate. There's probably a reason, even if it's not the one I mentioned.

[J. Clarke]

Sound like toolmarks to me. Toolmarks are the result of, well, not removing toolmarks. I can't see where striations about the size of the grooves in a phonograph record are going to provide much cooling anyway--if anything they'll provide insulation and prevent heat from being conducted into the plate. Might keep the disk from sliding, but I've never had that problem myself. In any case it seems to me that having it well stuck down is more likely to keep it from sliding than reducing the contact area.

As for "the ease of just lapping the plate", that's just another grinding process, removes the same things that sanding the plate with a block will remove.

If they're clearly machined on purpose that's a different story.

[Leon]

Show me a 12" diameter hook and loop sander? ;~)

[Nova]

I've had so many PSA disk that wouldn't stick to my 12" disk sander I gave up even trying. Franklin makes a "Sanding Disk Cement". I coat the back of the disks (even the PSA) with their adhesive, let it dry, and apply the disk. You have to use a heat gun to get them off. See:

Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[B a r r y]

Regular old rubber cement is excellent for attaching paper to metal, if both sides are coated and allowed to dry. I've used it on aluminum T-bar sanders for years.

I'd spend the $0.79 on a bottle and see if it works on the disc sander.

Barry

[Mark W]

First of all, I want to thank everyone for their responses and their help. (Especially John; I appreciate the time you spent typing in THAT one!) The more I looked at this disk, the more I decided those fine grooves are in fact tool marks caused by too rapid of a feed rate when machining the disk. I called Jet today, and spoke with them about it, and they pretty well decided the same thing. They said they were going to ship me a new disk and that I should have it in a few days. Well, I went back to the shop this evening with the intention of removing the disk from the sander, but I found the disk is VERY solidly pressed onto the motor shaft and that I don't have the means to remove it without the fear of warping it. So, I jointed a 3x3 of ash and some 80 grit PSA paper and went to work on the spinning disk. It took about 5 applications of sandpaper to get all of the grooves out, but I did manage to get them out and maintain flatness of the plate as verified by my straightedge. A few passes with some 120 grit, and it was nice and shiny. Then, I took the SAME sandpaper disk that wouldn't stay on before and stuck it onto the metal disk. It stuck with an insatiable appetite. I can only imagine trying to peel the thing off later when it's worn out. Now, what am I going to do with the other metal disk when it get's here? ;)

Thanks again everyone! Mark W

[Mark Jerde]

Get another motor...

-- Mark

[J. Clarke]

Glad you got it working.

[bridger]

send it to me......

[George]

Seeing is believing. Or as the old slogan "ask the man who owns one."

They're NOT tool marks, which would likely be spiral, and as I menti> >

[J. Clarke]

Given the events described in the other branch of the thread, there is only one possible response to this . . .

ROF,LSHIBAGASM

[John]

Mark

Depends on if Jet wants the old one back or not. If they don't, keep it as spare parts

If they do want the old one back, just refuse to accept the delivery when it comes, as I would BET that the one you have now, after all that work is SIGNIFICANTLY BETTER than what they are going to replace it with\

John

[Gary DeWitt]

I have one. Bought a psa hook and loop pad for my powermatic 12" sander. A bit hard to mount discs, because the table gets in the way, but it works. I just cover the disc with a piece of release paper that it came on, until I have the sandpaper in the right spot, then pull out the release paper.

I used laquer thinner to clean the disc of old glue, it's a fairly smooth aluminum disc, never had any adhesion problems, even when pulling hook and loop papers off.

I AM having problems keeping sanding discs (less than 1 year old) stuck to my cross cut fence, which is annodized alluminum, no matter what I clean the fence with. I'll try heat.

[Mark W]

I am thoroughly convinced they were tool marks, as they WERE spiral. Even if they were intentional, they were the source of the non-adhesion problem. I'm still going to closely examine the new disc when it arrives.

Mark W