tracking problems on delta drum sander 31-260x

[jim gossage]

The punch line is that I can't get my drum sander to track. This post is a total Hail Mary, 4 seconds left, on our 30, throwing the 40 yard bomb. If you guys can't help me, no one can. Delta service of course has been worthless. I just hate the thought of junking an otherwise functional machine.

I've had this sander at least 10 years and it worked well for most of that time and without significant tracking issues. 2 years ago I had some table elevation issues and stripped it half down and put it back together again using the manual as a guide to get the set up right. Everything is now level and square, table elevation works smooth, but the conveyor belt consistently moves to the right (when at the machine front) after about 5-6 belt rotations and starts to fray against the roller bed.

Here is what I have tried without avail, both with the table mounted on the sander (with and without wood running through it), and with the table removed and running on its own without a wood load (please see pics below but NOTE that the 2nd pic is upside down):

1. 1 old belt, 2 new belts, tried both directions.
2. Checked rollers and table: table flat within 0.004", roller runout 0.002".
3. Cleaned roller bushings.
4. Checking roller coplanarity with top of table, fine.
5. I have adjusted the rear roller so that it is exactly parallel to the table, and then adjusted the right side (RRA in pic) to be 1/8" away from the table (right drift seems slower), or 1/8" closer (drift is faster).
6. With each of the above attempts, I gradually increase tension on the belt with the front roller adjusters (FRA in pic) until the belt just starts to move forward (blue arrow); if I tension the left side more than the right, the belt really moves to the right (as expected); If I tension the right side more (even to the point where the left side is grossly loose), it seems to move less quickly to the right, but right it still goes. Even with max tension on the right it goes to the right - just doesn't make sense. I even replaced a belt because I was concerned that I had overstretched the belt and that was the problem.

I'm a reasonably smart guy and do research for a living, so I generally know how to analyze a problem. But this one has me stumped. I can't even think of anything else to tweak or measure! I would greatly appreciate any of the learned opinions out there. I have no problem spending money for a new one, but I just hate to take stuff to the dump.


top view with belt.jpgtable and rollers.jpgside view with belt on.jpg

[Tim Elett]

Maybe belt could be slipping on drive roller? Can you flip the rollers 180, sounds like you checked bearings

[Dwayne Watt]

It took a new conveyor belt to resolve this similar problem on my drum sander. Perhaps the new belts you attempted to use were defective? I purchased a belt from Klingspor that resolved my issues. I was skeptical when I opened the box because the new belt was much thinner backing material than the cloth backed belt it replaced, but it has held up for the last 6 months without issue.
Is the table perfectly square itself since you are using it as a reference? The rollers need to perfectly parallel to one another not necessarily aligned with the table. If they are too far out of "square" (think parallelogram shape) the belt may appear to track oddly as well. Just some thoughts...

[Holmes Anderson]

Jim, I have the same crummy drum sander. New belts seem to track erratically until they are stretched out or something. When I adjust the belt tracking, I just make gradual adjustments while watching the belt track. It can pretty much be adjusted to the point where there is little/no contact on either end so drift in either direction can be reduced but usually not eliminated entirely. Have you maxed-out the fine adjustment with the allen head machine screw? If so, then you migt have to make coarse adjustments with the bolts. Both the front and rear rollers can be adjusted that way. It is possible that those bolts loosened on your machine and the "fixed" roller position has changed so much that the fine adjustment is useless.

Re-reading your post, it sounds like you have adjusted both rollers. Rather than setting the rear roller relative to the table, try setting the rear roller relative to the front roller. I'm fairly sure that the slots are so long that the belt can be forced to track hard in either direction. Relative to your first photo, try increasing the distance between the front and rear rollers on the right side (and/or decreasing the distance on the left side) by making coarse adjustments to either or both the front and rear rollers. The tracking is primarily a function of how parallel the rollers are to each other.

[Mel Fulks]

Agree with Dwayne. And I think Klingspor still sells cloth and paper. Don’t store the belts vertically. Don’t leave tension on when machine
is not in use.

[John TenEyck]

I had the same sander and even a new belt from Klingspor didn't completely cure the problem. I had to leave the belt loose on one side to keep it from tracking too far off on the other, but it still did over several hours of use. I'd loosen the adjusters enough to slide the belt over, and the process repeated. I sold that machine for what I paid for it, and was glad to be rid of it. The double drum sander I have now has some type of composite belt that tracks straight and true and never needs adjustment.

John

[Jim Morgan]

Did you try turning the belt around? If the belt is the problem, it should then track to the left. This should help to narrow down the possibilities.

[jim gossage]

Thanks guys for your speedy replies.

• I don't think the belt is slipping on the drive (rear roller) simply because the belt is clearly moving after I give it enough tension so that it doesn't slip; but one thing I haven't tried is flipping the rollers end for end.
• I have also tried both fine and coarse adjustments to the front roller tension but still can't stop it from going right, and it goes pretty fast, usually within 5 minutes at a mild speed.
• I have flipped all the belts and that never fixes the problem so I have come to believe the belts are good. And I think the current one is Klingspor.
• I also like the idea about making sure the rollers are parallel to one another, not sure I've double checked that yet.

The oddest thing is that even when I move the right end of the rear roller away from the table AND start tensioning the right roller, it still goes right; no matter what I do I can't get it to go left. Weird! I'll report back after I try some of your suggestions.

[Earl McLain]

Not a proper fix, but on an old Craftsman belt sander (6" x 48") i was able to "cure" the belt drift with a single wrap of painter's tape around the center of each idler roller. Worked until i replaced the whole sander. That may not work in your case, but if checking the rollers being parallel and flipping the belt don't help--might be worth a shot. Good luck!!

[Darrell Bade]

If you really want a short belt to track proper easily the roller should have a small taper from the high center to both edges. That is why the wrap of tape in the center works.

[Bert McMahan]

I don't own one of these so this is just a guess, but is there any way the rollers are too low compared to the table, and it's the table itself that's pushing the belt to one side?

I could imagine an extreme case of, say, a bunch of diagonal grooves in the table that pushed the belt to the right. I could see that extra drag coming from one corner of the table being higher than the rollers, meaning there's a corner for the belt to catch and pull to the right.

Can you adjust the vertical axis of the roller mounts on that unit? Can you measure the offset from the roller to the table and see if one corner is higher than another?

[mreza Salav]

Can you flip the roller left/right to see what happens? Is there any chance for whatever reason the roller is not true cylinder anymore? Try wrapping a few rounds of tape over the right side to make it thicker (gradually) and see if it helps.

[jim gossage]

SUCCESS! I'm not sure what worked but here's what I did, pretty much all at the same time:

1. I cleaned the rollers and checked their straightness (+/- 0.002") and diameter (+/- 0.001").
2. I flipped the front roller end for end as suggested by someone but the rear could not be flipped due to design.
3. I slightly canted the rear roller away from the table on the right side.
4. The roller tops cannot be made flush with the table top, but I made sure the rear roller was parallel to the top; the front roller design is such that it is always parallel.
5. With the rollers adjusted parallel to each other, and enough tension to move the drive belt, the belt quickly drifted to the right . However, this time I was able to tension the right side enough to stop the movement and even drift slightly to the left. The left side is completely loose but I am not going to let perfect be the enemy of totally functional.
6. I next tried the tape in center trick as suggested (3-4 layers of painters tape) but it had no benefit relative to #5 above.
7. I took off the tape and went back to #5 tension settings, no drift.
8. I put the table back on the sander and my niece just happened to come for a visit today and brought a cutting board for renewal. The sander worked perfectly.

I'm not really sure which step/s helped, but I have a fully functional drum sander for the first time in 3 years! Thanks again for your help. You guys rock.

[mreza Salav]

I was going to ask for an update. Glad to hear you got it fixed.