Belt Sander Question

[algale]

I think the mystery is solved.

Removed the new ceramic belt and I put on some old A/O belts. I had to adjust the two bolts that the idler drum cams ride on down significantly to do so. But once I did, the old A/O belt tracked fine and was against the back up platen.

Tried to reinstall the new ceramic belts sold by Shopsmith (but made by Sunmight), and had to keep taking it off and raising the 2 bolts higher and higher to raise the idler drum. FInally, I could not raise them anymore and have room for the cams to turn in the casting boss to release belt tension or increase belt tension. The belt tracked but was flapping a good 3/32nds' off the platen.

Conclusion: the new ceramic sanding belts sold by Shopsmith but made by Sunmight are simply too long to be properly adjusted to the Shopsmith belt sander.

Caveat emptor.

I'll be in touch with customer service.

[edma194]

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.

That does sound like a lot. Do you have too many washer under the platen? I'd expect 1/16", even 1/8" maybe. Will check mine later.

Tried to reinstall the new ceramic belts sold by Shopsmith (but made by Sunmight), and had to keep taking it off and raising the 2 bolts higher and higher to raise the idler drum. FInally, I could not raise them anymore and have room for the cams to turn in the casting boss to release belt tension or increase belt tension. The belt tracked but was flapping a good 3/32nds' off the platen.

Conclusion: the new ceramic sanding belts sold by Shopsmith but made by Sunmight are simply too long to be properly adjusted to the Shopsmith belt sander.

I have had trouble adjusting both Shopsmith and other brand belts at times. Maybe the belts aren't that consistent even from the same brand? In my case some of them are rather old. I keep all my sandpaper in a 'safe', a sealed plastic box with a bag of desiccant in the bottom. I'm beginning to think that shrinks them up and after stretching from use they go on and off easier. Your problem is the opposite though, and there is going to be some maximum length the sander can adjust to without raising the platen.

[chapmanruss]

So, if it helps here, below is one of the posts I made in the thread "Check Your Belt Sander Platten Screws" that David referred to.

Depending on when your Belt Sander was made it may have a washer behind the Back-up Plate (the listed part name instead of Platten) or 2 washers or no washers at each of the 6 holes. In checking different era Manuals, the first Manual from 1956 has 1 washer behind the Back-up Plate. The Manual dated 7-72 (when Shopsmith Inc. was preparing to restart production) has 2 washers behind the Back-up Plate. The Manual from 1-89 and the current parts list have no washers behind the Back-up Plate. The washers were use as spacers between the Back-up Plate and the Inner and Outer Frame castings to the tabs where the Tinnerman Clips attach. The Washers change the Back-up Plate position in relationship to the Drive and Idler Drums. Having some washers missing and depending on where they are missing may cause your Back-up Plate to not sit flat across the entire surface.

EDIT

So, I did just go out and check my Belt Sanders. My Belt Sander made in December of 1977 has the 2 washers behind the Plate at all six holes and the screws were tight. This is my primary Belt Sander with the Dust Collector Chute upgrade. My other Belt Sander I currently have is one I recently acquired and haven't started restoring it yet. The screws are tight and it has the 2 washers behind the Plate. The washers are thicker than standard ones.

The other Belt Sander I recently acquired is a Goldie from the 1960's. The Spacer Washers are thicker than standard Flat Washers.

I don't know how the Back-up Plate sits in relationship to the Drive and Idler Drums on newer Belt Sanders without spacer washers. It is possible the Mounting Tabs moved outward on the newer castings.

The Back-up Plate should be at least even with the plane between the Drive and Idler Drums or actually slightly above. Think about longer boards extending past the Drums while sanding. If the Back-up Plate is below the plane between the Drive and Idler Drums, longer boards will be sanded by the Drive and Idler Drums surface first and not against the Back-up Plate.

I realize this has nothing to do with Belts being too long to be properly adjusted on the Shopsmith/Magna Belt Sander. That has been pretty well covered.

[algale]

Follow up. Shortly after I wrote this, I began to suspect that my problem was that the torsion spring inside my idler drum was, to use the technical term, kaput. Even when properly tensioned, it didn't have enough oomph to push up against the belt. So I ordered a new idler drum assembly from Shopsmith. It was back ordered and then when it came I was busy with a bunch of stuff. I just got around to installing it. It solved all the issues I was having. I can change back and forth between my older belts and the new ceramic belts I got from Shopsmith without manually changing the height of the bolts that the cams ride on. And the belt tracks closer to the platen without flapping. I do think that the newer belts are a bit longer, but with a properly functioning Idler drum the belt sander can handle it. The idler drum assembly was an expensive part, but it should be good for the rest of my life.

[chapmanruss]

algale,

Thanks for the update. It is always nice to find out the solution to a problem discussed here.

[DLB]

...And the belt tracks closer to the platen without flapping...

Congratulations. Did CS help to solve this? Going back to your original question here, are you saying that the belt is still not in contact with the platen when tensioned but not sanding? Mine is much different than that, it is in firm contact with the platen at all times. I think I have a newer (new to me) Belt Sander in my attic, if so I'm going to have to compare.

- David

[algale]

...And the belt tracks closer to the platen without flapping...

Congratulations. Did CS help to solve this? Going back to your original question here, are you saying that the belt is still not in contact with the platen when tensioned but not sanding? Mine is much different than that, it is in firm contact with the platen at all times. I think I have a newer (new to me) Belt Sander in my attic, if so I'm going to have to compare.

- David

]

No, this had nothing to do with customer service. The new belt is not tight against the platen when not sanding. But it isn't flapping anymore, either.