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Splicing grinder belts


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I got a box of 4x132 grinder belts from the industrial surplus place, with an eye to cutting them down to fit my 2x90.

The original splice is some kind of film, which I was able to cut and peel off fairly easily.


After splitting the belt into two pieces — simply by tearing it down the middle — I cut one half down to 90” and spliced it together with a piece of cotton cloth (cut on the bias) glued down with polyurethane adhesive (Gorilla Glue). A backing board, a steel block in a plastic bag, and a C-clamp, and we’re good to go.



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A few more photos.

 The original splice, split and with the tape ground off of one side:

My splicing board has a pencil mark showing the correct angle. Once the length is marked with a bit of soapstone, that mark is put against the angle:

The belt is cut (I use an old handsaw):

The two ends are butted together and clamped to the splicing board:

The surfaces are dampened with a wet paper towel, a layer of Gorilla Glue and the fabric splice are applied, the steel clamping block is put in a plastic bag, and everything is clamped together for two hours:

This is the underside, after the glue has cured:


And the front. A bit of the coating came off the belt, but none of the grit.


And this is after the splicing fabric and excess glue have been trimmed from the edges:


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  • 2 weeks later...
  • 2 months later...

JHCC - Thank you for the splicing instructions.

I bought a 4 by 108 belt grinder last Oct. but no belts. Suppliers for that size are rare (also I'm minding my cash flow during the current situation.) Your instructions show that the splicing isn't as complex as I'd originally thought.

I'd like to confirm the splice angle as 20 degrees (a protractor held onto the laptop screen is only so accurate.)


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I've never actually measured the angle, but just copied the angle of the existing splice.

An update: the cotton fabric didn't last particularly long. I've ordered some poly/cotton bias tape, and I'll report back on whether or not it holds together better.

13 hours ago, Don Shears said:

I bought a 4 by 108 belt grinder last Oct. but no belts.

If you want a couple of 4x132 belts in 36 grit ceramic, send me a PM. I'm sure we could come to an arrangement.

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  • 9 months later...

Long-overdue update: in practice, the bias tape tended to last significantly shorter than the belts themselves, and I ended up having to reglue a couple of the belts when the fabric let go. After the last rather spectacular rapid unscheduled disassembly (which fortunately caused no damage apart from a bit of a scratched wrist), I decided to seek other alternatives. 

And so, after wandering for a time through the lands of Google, I encountered the following method, which I here assay. 

The key ingredient is fiberglass strapping tape of a variety I’d not previously encountered: where the fiberglass is a woven cloth rather than longitudinal fibers. (The original instructions recommended “Scotch Extreme Application packaging tape”; I used “Bunker Hurricane Tape”, as that was what my local hardware store had on the shelf.) 

The belts are cut to length and the backs roughened on either side of the splice. A layer of contact cement is applied to the backs and allowed to dry.

So here I’ve set up five belts to glue. They’re all clamped down to a backing board, aligned with the front edge to keep them straight. I’ve put some pieces of round bar between the belts to keep them separated while the glue dries. 


The tape is applied first to one end and then the other. 



The tape is rolled down with a brayer.


This is repeated until the whole stack is done. It’s probably not necessary, but as recommended in the instructions I was following, I clamped everything to cure for an hour or two. 


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Interesting.  A couple of things to note:

  1. There are companies that will make custom belts of virtually any reasonable dimension for you.  Certainly at a premium, but not unreasonable.
  2. When splicing thinner is always better.  I really like your updated procedure, especially the spray coating
  3. If belt bump with the splice is an issue a rolling platten may be the solution.
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UPDATE: I took a look at the belts during my lunch break today, and things don't look good. The tape was bubbling, and when I put one of the belts on the grinder and tensioned it, the joint blew apart instantly. The adhesive on the tape did not hold at all and was actually still sticky.

I've done a bit more research on the Hurricane tape, and it turns out to have been a bad choice. It seems that it's a pressure-sensitive, water-based adhesive that stays removable for up to two weeks. Oh, well.

Next step is to get the originally recommended tape and try again. With luck, I should be able to get the bad glue off these five belts so they won't be wasted.

Lesson learned: don't overcommit to an untested method.

39 minutes ago, Latticino said:

There are companies that will make custom belts of virtually any reasonable dimension for you.  Certainly at a premium, but not unreasonable.

Very true, but you know how cheap I am. By buying surplus and investing a little time and very little money, I'm getting belts at less than a quarter of what even standard-sized belts would cost.

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It figures, there was a guy in Anchorage that made bandsaw blades and abrasive belts. He had a machine for making belts, it cut, feathered the ends and used a heat cure tape and it was done in maybe 30 seconds unless it was a weird length but he had a measuring machine too. Unfortunately The Purple Hippo hasn't been around for years, his son didn't want to take over the business when the old man retired. 

Watching him make belts could give a guy the wrong idea though he did say you could use an iron but forget about letting the wife know or try to use it on clothes again. 

I'll keep my eyes open, you never know.

Frosty The Lucky.

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Quick detail: I thought that while I was still looking for the proper tape, I might try flipping the Hurricane tape over and using contact cement on both it and the back of the belt, just as an experiment. I had sanded the old adhesive off the belt and applied a new coat when I discovered I’d made a serious mistake: instead of contact cement, I’d been using rubber cement. Oops. 

Lesson learned: don’t focus so hard on finding the right tape that you end up getting the wrong glue. Tunnel vision is real. 

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