Shopsmith Forums

When the belt sander is set up and operating properly, should the sanding belt be in constant contact with the platen, top to bottom, even when you are not pushing a work piece against the belt??

I've just had mine completely apart for maintenance (first time in a decade). I pulled a lot of sanding belt threads out from between the bearings and drive drum. I also disassembled, cleaned, lubed and reassembled the idler drum assembly. I also watched Nick Engler's sawdust session 3 times and made sure I did as Nick did.

I mounted a brand new sanding belt I just received direct from Shopsmith, pushed the button on the tensioning knob one time to tension the belt tension (I had reset the tension on the knob with 4 counterclockwise turns before putting the belt on), started the headstock, and adjusted the side-to-side tracking. The belt is running true side-to-side. But by no means does the belt run against the platen from top to bottom. Maybe a 3/32nds gap when I don't push a work piece against it. Is that normal??

Al

Did it before? Not sure the platen is supposed to be a bearing surface until you start sanding.

jsburger wrote: ↑Wed Dec 20, 2023 9:52 pm Did it before? Not sure the platen is supposed to be a bearing surface until you start sanding.

I can't recall if it did before. But that's the exact question, whether the platen is supposed to be a bearing surface before the sanding begins.

I would prefer it to just clear the platen when not under load. Think of it as the same as the bandsaw backup bearing.

If it was not designed that way IMHO they goofed.

A straight edge drum to drum should tell the tale.

Mine, mid 80's, has always had firm contact with the platen whenever the belt is tensioned. I'm not saying it's right, but it has always been that way.

- David

So now I gotta check mine!

Surprise! Platen is 3/16 to 1/4 above the straight line between the drums.

A recipe for wear at the ends of the platen.

JPG wrote: ↑Wed Dec 20, 2023 11:02 pm So now I gotta check mine!

Surprise! Platen is 3/16 to 1/4 above the straight line between the drums.

A recipe for wear at the ends of the platen.

Can you mount a belt to see whether when properly tensioned, either static or in motion, the belt is fully in contact with the platen?

DLB wrote: ↑Wed Dec 20, 2023 10:57 pm Mine, mid 80's, has always had firm contact with the platen whenever the belt is tensioned. I'm not saying it's right, but it has always been that way.

- David

Helpful, David. I'd love to get confirmation from one or two others members.

The new belt I mounted is one of three brand new belts from Shopsmith but is not a Shopsmith-brand abrasive. I think it may be a hair short as I had to use the adjustment bolts to substantially lower the idler drum to mount the belt. With the lower idler drum, perhaps there just is not sufficient torque left in the old torsion spring inside the idler drum to tension the belt properly. I will remount an old belt and see if that helps. If not, it may be time for a new idler drum assembly.

algale wrote: ↑Wed Dec 20, 2023 9:32 pm The belt is running true side-to-side. But by no means does the belt run against the platen from top to bottom. Maybe a 3/32nds gap when I don't push a work piece against it. Is that normal??

There should be a couple of spacer washers under the platen at each mounting screw location. Could these be missing? (From other discussions here I gather that the actual amount of spacing has changed over the production years. The casting itself has also changed. So YMMV.)

- David

DLB wrote: ↑Thu Dec 21, 2023 8:13 am

algale wrote: ↑Wed Dec 20, 2023 9:32 pm The belt is running true side-to-side. But by no means does the belt run against the platen from top to bottom. Maybe a 3/32nds gap when I don't push a work piece against it. Is that normal??

There should be a couple of spacer washers under the platen at each mounting screw location. Could these be missing? (From other discussions here I gather that the actual amount of spacing has changed over the production years. The casting itself has also changed. So YMMV.)

- David

No, my spacer washers are installed. I think I have the mystery solved. See my next post.