Can you re-join broken sanding belts ? 

Note: Worked out well for a first attempt. I might run a file or a small grind stone over the grit side join to see if the small "hump" can be reduced. It will probably wear away with use as well. Cheers Rob

I used to have an old 4' long linisher that took ludicrously expensive 3" wide belts, so eventually I started making my own. The two main factors that seemed to make the join let go was the glue softening from the heat generated as the belt flexing over the rollers or from the actual friction of metal removal (You already seem to be on top of that with the heat resistant contact adhesive), and not having the belts 100% straight. If it's even slightly out of line the join will start coming apart from the tightest edge. To make these belts as straight as possible I'd just clamp a temporary jig together from of a ruddy great slab of steel off cut and some angle iron. I clamped the angles to give me a nice and even 3" gap between them, then after "Degritting" the overlapping ends of the length of emery roll, I'd lay the belt in position and put clamps on to keep it from moving about (8+ foot of 3" belt can get hard to keep under control. :D). Once it was all in position I'd glue up the ends, lay them flat, and using a couple of the biggest G clamps I have, crush a 3"∅ stub of barstock onto the join. They were never quite as good as the genuine belts, but I'll happily accept 80% as good for 20% of the price any day of the week. :)

Hello Rob, It looks like it worked really well... As you said the squashing in the vice make sense... Good tip... Cheers. Paul,,

I purchased a box of 1 x 42 inch sanding belts at an auction for a couple of dollars. Apparently, they were pretty old because every one of them began breaking at the seam when I tried to use them. I tried every glue I had attempting to repair them. Nothing worked. Finally, I stuck a 1 x 6 inch strip of duct tape across the seam on the back of the belt, laid it on a marble slab that I have on my work bench and used a roller to make sure the seal was good. It worked like a charm.

Regluing broken belts is of course nice. There are more videos showing that. For a mini sander no spare belts were found. By making a new, longer , arm for the tension wheel belts were found. However they were 62 millimeters wide and my grinder used 30 mm. Made a cutting tool that cut out a 30 mm belt. The remaining 32 mm had to pass the cutting tool once more. Cutting from the inside be pressin a Stanley blade through workded well, but slowly. Each cut was some 10 - 15 mm long. But I have belts1

I was surprised that they held together, if you've run out of belts it's a good fix. On my 4" belt sander the belts tend to wear out before they break. Never throw them away though, great material for protecting soft metal when held in the lathe chuck. Which I believe was another trick I learnt from you 👍🙂 Cheers, Alan.

Once knew a shoe repairman. He used shoe glue to mend sanding belts. It seemed to work. He also pounded his joints to set the glue. Don't know what the glue was, but the solvent reeked.

Hi Rob, good fix to get more life. Humidity is your enemy, store all your belts in the house (even your repaired ones), you will get much longer life. I watched an ex boss of mine going loopy at a supplier following multiple failures on big 6" wide 6ft long belts. Turns out they were stored in a tin shed with lots of year round condensation, this was in the days when supplier sales reps knew their onions, he got straight to the root cause. Cheers, Jon

I make my own belts to Rob . I use gorilla tape to join them and then use a hot iron with a damp towel . Works great .. Cheaper than buying them as well !!

In the past when my contact adhesive has dried up, I've had success resurrecting it by mixing with general purpose paint thinner.

Once you glue the belt put the seam in a press. You can use anything to press it flat. Drill press, press, clamps etc. I leave them over night. Nice and flat and smooth.

Bought a lifetimes worth of "quality" belts when Masters closed down. The joint of all off then let go in storage. So far CA glue and Epoxy any high strength tape haven't work. Trying the high strength contact, squashed in the vise using two parallels, reinforced with high strength tape. So far so good. Need to clean the joints with a file first.

Those lap joints are terrible. One idea is to perhaps add another idler to your frame so that you can run a common size like 48” unidirectional belts (no lap joint). You will also have a good variety of abrasive types to choose from so you can buy quality belts that last.

G'day Rob. Good idea thanks for the video keep on keeping on.

Had a bunch of cheap belt sander belts go like that, they actually fell apart after being stored in the workshop for a few months. Humidity, I guess. Used evo-stik on them, it worked for long enough to get the job I needed done, done. The stuff big conveyer belts are glued with is a contact adhesive as well, black self-vulcanising stuff which gets a bond on the rubber. I also finally got fed up with the (leather) flat belt on the Schaublin breaking its lacing, so I degreased it, scarfed the joint and glued it together with super glue. It's held for the last 6 months, no problems as yet. I was kinda worried that the cyano would make a hard point that would crack, but it doesn't seem to have happened, might be worth a shot on sander belts as well.

I will have to try this technique out. Nothing more frustrating than breaking / tearing a new sanding belt. Thanks for sharing this!

Rob,great tip.I have a few 1 inch belts that have come apart.Cheers!

Hi Rob, It is hard to tell from the angle of the video but it looks like the platen is a little to far forward at the top and maybe catching and peeling off the joint on the inside over time. Perhaps a little adjustment might stop them breaking so often. I have used fibre glass tape right around the inside which helps, but in the end as my belts are worn usually worse than your examples, + as there is a cost to the tape and glue, I gave up and went back to buying new ones. Like you I split them in 2 and use the left overs for other uses so I still save a buck or 2. I do what I can to avoid spending hard earned $ but now days I'm a bit more pragmatic. if it's 90% worn out its only worth 10% of what I paid for it.

20 Years ago I lived near a abrasive factory and they had a skip outside they filled with offcuts. It was supposed to be locked but occasionally they forgot to lock it . What a treasure trove. Some "offcuts" were 2 metre long 1 metre wide! I am just starting to exhaust those supplies. With all the free material I set up a production line for belt making shaving off the strip for the join was the trickiest. However the glue proved the biggest weakness . I mostly sand wood and the heat of sanding softens the contact glue and any heavy and slightly prolonged pressure results in the glue softening and the joint giving up. Age has not been a problem I still have multiple belts hanging up that are OK until they get quite hot. I see they make contact glue for rubber roofs. That should be able to stand a fair bit of heat build up.

Good stuff Rob--economy in the workshop is not to be sneered at---its sensible

As a few others have said, It's heat buildup that weakens the glue joint. I've only ever had one belt fail,scary shit. Pretty sure the ingredients for belt glue is a fairly closely guarded secret. Seen a few pl try this but none with reliable or trustworthy results, your grinder is fairly slow so shouldn't be too destructive when it explodes😁

Hi Rob, had a batch of Zirconia belts, the blue ones made in Perth for my multi tool, local business, he won't disclose the type of glue. They use a press and heat to make the joint They all blew apart after approx 2 years storage , quite dangerous as they fly across the workshop, definitely have a shelf life. Tried just about every adhesive and they blow apart, mind you the multitool is directly attached to a grinder, 2 pole motor, looks like yours is a 4 pole motor running a lot slower. Ordered various belts from China last year and they hold up but suspect they will also come apart. I think the secret is to buy limited stock and replace as you need them. I now stand to one side and a full face mask and nervously sand away!

Hi Rob , I found a really good deal on belts one time and bought a bunch of them. Turns out they would only last a short time and break at the joint of course. I still had some old belts in my supply and went back to them and they lasted a very long time until wearing out but not breaking at the joint. I did some playing with the broken ones to reuse them with limited success. That got me to looking at the difference in the belts and found the ones breaking had a very short join area like the ones that you were regluing but the good ones had a much longer gluing area say about an inch long. It seemed to me that was a big advantage to them holding together. That was as far as I had gotten with them so far so find this video quite interesting. I imagine there will probably be some follow up down the road on this video. Dale in Canada 🇨🇦

I found that this works well if you’re not putting too much heat into the belt, I found once the glue got hot it would let go.

I've had some belts come apart & never thought to try & join them back together. They'd had some use anyway & I'm not sure I could trust re-glued ones on our polishing spindle back-stand as they let go with a bang! ( ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-JopHDzQ3t8E.html ) Well worth a try on slower speed linishers though & if you're having trouble getting the size you need you could maybe make your own from scratch?