Repairing sanding belts?

[JoeLee]

Hi,

What I can tell you about 3M's process from when I worked in their abrasives division a long time ago, is that the adhesive is proprietary and made by them for their own use. Depending on the product being produced, they used either butt joints or skivved joints. They used a special fiberglass tape with the glue to form the join. The tape had to be stored at -30F and had a room temperature life of about 45 minutes before use or it had to be tossed. The seam was pressed with a heated bar between 230F and I think 280F and at 5 to 15 tons of pressure to make and cure the join. Time and temp varied by width and joint type. It generally took between 30 seconds to 1 minute to make the join. And then the belt was left to cure for 24 hours before it could be used.

The materials did age out at around 5 years and those were disposed of.

That's what I thought and I did mention it in my post #21.

The Sait belts that I have use the fiberglass reinforced tape.

That is very interesting, thanks for posting it. It clears up a lot of guessing. I'm sure a lot of R&D went into that process.

But in this day and age I would think there is something out there that might work.

JL.............

[J Tiers]

I eliminated the middleman, and when a bunch of belts came apart (the glue turned really sticky and gooey), I just moved them over to being used for "strip sanding", either on the lathe, or just for general bench work. They work fine for that, I needed some of those anyhow, and now I have a wide variety of grits available.

Not worth my time to screw around with the gluing. Especially since I got the cubitron belts that work 6x better.

[challenger]

I eliminated the middleman, and when a bunch of belts came apart (the glue turned really sticky and gooey), I just moved them over to being used for "strip sanding", either on the lathe, or just for general bench work. They work fine for that, I needed some of those anyhow, and now I have a wide variety of grits available.

Not worth my time to screw around with the gluing. Especially since I got the cubitron belts that work 6x better.

Definitely not an efficient use of time but, imo, it's rewarding to solve a problem if one has the time and obsessive personality 😁. The later is my excuse.

[dian]

i have glued 2x72 belts with flexible instant glue in the past. no problem, no tape. the hardes part was to ge the alignment right.

[Rich Carlstedt]

i have glued 2x72 belts with flexible instant glue in the past. no problem, no tape. the hardes part was to ge the alignment right.

Name or photo please

Rich

[Bob Engelhardt]

i have glued 2x72 belts with flexible instant glue in the past. no problem, no tape. the hardes part was to ge the alignment right.

Like Loctite 4902? $$$$!

[Rich Carlstedt]

Wow,$ 70 for .7 of an Ounce....that seven tenths of an ounce !

Rich

[dian]

it was not locktite but some instant glue designed as flexible from a local diy store. name and picture wont help much because you probably wont be able to get it over there any way, its several years back.

[Spades]

I had a problem with a substantial quantity of smaller 12mm wide belts coming apart at the glue joint. I tried numerous methods and glues which all failed miserably within just a couple of rotations.

The original glue used is a thermoset which creates problems when sanding steel, aluminium etc. where the developed heat softens the glue, it also has ageing problems where it fails after about 12 months.

I have recently had very good success with Loctite Powerflex super glue. It is a rubberised glue which has lots more flexibility which I believe has been the main problem in my case where the belt wheels are quite small in diameter (about 15mm).
I scrape all of the old adhesive off both mating surfaces with a blade, then lightly sand with 120grit, and then wipe over with Acetone.
The Acetone shows up any glue that has been missed and needs to be cleaned off.
I then smear a thin coat of the Powerflex over the entire face of one joint surface.
Align the faces and press together, clamp and leave it to set for a couple of hours - you may get away with less time.
It's important to ensure that the leading edge of the joint is well stuck as this appears to be the primary failure point.
I have no idea how this would work on larger belts and the quantity of glue required may make it uneconomical.

[DR]

I used to buy custom size sanding belts from converters. Converters are companies that make belts to your size requirement from raw stock. They're usually independent from the big guys like 3M, Norton, etc, so they can't supply belts in the newer, proprietary super abrasive types. Surprisingly custom belts aren't very much more than a close in size standard belt.

Jet and Western Abrasives in Los Angeles is a place I used quite a bit. That's one company and not affiliated with Jet Machinery. They were always helpful in suggesting an abrasive they had in stock for the material we were sanding. They will gladly give advice, but they won't sell direct to users, you have to order through a local industrial supply outfit.

I always wondered if they wouldn't be a source of info on belt repair materials. A phone call might yield some good info.

[J Tiers]

............................................

The original glue used is a thermoset which creates problems when sanding steel, aluminium etc. where the developed heat softens the glue, it also has ageing problems where it fails after about 12 months.

................................

A "thermoset" glue is one which does not soften with heat. You are confusing "thermoset" with "thermoplastic". Thermoset glues have components which react when heated to change into a different material that holds the parts together, and which is not heat-sensitive. Like "Bakelite", which does not soften to any particular degree with heat, but is a thermoset material, where phenol and formaldehyde react to make a hard solid.

I have NEVER seen a manufacturer glue joint fail by softening with heat.

What every stinking one of the SOB's has done is soften and turn gooey while sitting on the shelf waiting in reserve. Then when put in place, they hold for one turn around the pulleys, or maybe a few more, only to literally slide apart, leaving a sticky residue on each side of the joint.

That is without any work being sanded, so no heat buildup.

[challenger]

A "thermoset" glue is one which does not soften with heat. You are confusing "thermoset" with "thermoplastic". Thermoset glues have components which react when heated to change into a different material that holds the parts together, and which is not heat-sensitive. Like "Bakelite", which does not soften to any particular degree with heat, but is a thermoset material, where phenol and formaldehyde react to make a hard solid.

I have NEVER seen a manufacturer glue joint fail by softening with heat.

What every stinking one of the SOB's has done is soften and turn gooey while sitting on the shelf waiting in reserve. Then when put in place, they hold for one turn around the pulleys, or maybe a few more, only to literally slide apart, leaving a sticky residue on each side of the joint.

That is without any work being sanded, so no heat buildup.

So where does one get thermoset adhesive to repair the 185 1/2" belts broken by non-use 😬

[boslab]

Has anyone seen the new(ish) hot melt PU adhesives, they come in a metal cartridge you stick in the gun, may well be the abrasive belt solution

https://www.gluegun.com/collections/pur-glue-guns/products/infinity-pur-3000-complete-kit?variant=262070240

im seriously thinking of investing
mark

[J Tiers]

So where does one get thermoset adhesive to repair the 185 1/2" belts broken by non-use 😬

Don't know, never looked. The old degraded crap is so hard to remove entirely that I just used the belts for hand strip-sanding

[Jonesy]

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