Need a particular tape or adhesive

I guess adhesives are a kind of tool?

I’m making a lot of foot files (for rubbing off calluses) from oak and strips of wet-dry sandpaper about 1 1/2" wide and 12" long. I need a kind of adhesive or tape to attach the two together. It needs to be fast to apply, thin, uniform, strong and water resistant. The oak will be already finished for water resistance.

I’ve used 3M high-strength spray adhesive, but it needs to be applied to both surfaces, and masking the wood piece is time consuming. A spray that can be applied only to the sandpaper would work, and so would sheets of double-sided “tape” I could apply to sheets of sandpaper, then cut to size.

Anybody have any ideas? Thanks in advance!

I normally use the same 3M spray adhesive, or contact cement, whenever I glue sandpaper to something but contact cement shares the same problem of needing to be applied to both surfaces. Perhaps you could make a reusable stencil for applying spray adhesive instead of masking? Or apply contact cement with a brush?
Other ideas: Carpet tape (double-sided) sticks like mad and should be economical, it also comes in sizes close to 1.5in. A good hot glue gun with a wide nozzle would also do the job well.

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Oh, something else I just thought of: could you use self-adhesive sandpaper? It is supplied on rolls like tape and has a peel-and-stick backing. That also reminds me of “grip tape” used to add nonslip surfaces to things like stairs or skateboards. Some of those products are rubbery but others are basically heavy-duty sandpaper and would easily work for removing callouses.

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Thank you sir! That’s an excellent idea. I think I’d only seen that in disks.

Great suggestions Mecha. Hot glue may not be the best choice in this application as these products are typically stored in the bathroom where humidity levels are high.

Most hot-melt adhesives should be totally unaffected by water, they’re essentially just plastic that’s melted by the gun and then cooled to set. As long as it’s not super humid while the glue is being applied I don’t think that would cause a problem.

Agreed it could work, but may not be the best choice that’s all.

From what I understand, hot melt glue is pretty water-resistant. I’m not inclined to use it because I don’t know how to apply a thin, even layer that won’t cause any squeeze-out to be cleaned up later. But maybe there’s a machine that does it.

Hot melt is extremely water-resistant, that’s one of the reasons why I suggested it. Moisture will destroy the wood long before the hot melt degrades. It’s also a bit flexible which is nice because it can give a little if the wood warps. There are special nozzles for hot glue guns that spread the glue in a wide, even, stripe. Some have serrations built into the nozzle so they work like a notched trowel leaving an even layer behind. Search for “wide glue gun nozzle” or “sawtooth glue gun nozzle” More serious glue guns often have a stroke adjustment so they dispense a fixed amount of glue per trigger squeeze. Then it’s just a matter of setting the adjustment. If you’re making a lot of these it might make sense to buy one of those to make the job easier.

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Thanks Mecha, I’d never seen those nozzles. I would wonder if they leave a thin enough film of glue. It needs to be paper-thin, so there is no squeeze-out. Also, it doesn’t have a very long open time, right?

I think for now I’ll try that self-adhesive sandpaper you suggested. If that doesn’t work, 3M and I guess others make wide double-sided tape that looks feasible, also sheets of adhesive “transfer tape” that have no actual tape at all! They’re just adhesive. Kind of pricey, but manageable in the amounts I’m looking at.

The open time on hot glue varies by the formulation, some of them can be quite long, I’ve seen some claiming up to 3 minutes though I don’t have personal experience with those. I understand that you don’t want any squeeze-out, but I don’t think the risk of that is very high because you can control how hard you push the sandpaper down into the hot glue and avoid squeezeout by simply not pressing too hard. I don’t think squeezeout would be much of a problem.

Hm, I wouldn’t trust myself to apply the sandpaper without pushing it down, at least in some spots. Also it’s hot. I think I would go with something like construction adhesive over hot glue. But no liquid glue at all sounds best, like that self-adhesive sandpaper, or those double-sided adhesive sheets, I found.

Oh, you would need to push it down, you just wouldn’t push so hard you’d make a mess. Think about a sandwich: you put the top on it and hold it to eat it, but you don’t press down so hard on it that you squish all the filling out. Press carefully down on on the sandpaper while you’re watching to make sure the glue doesn’t ooze out. A block of scrap wood cut to the same size as the sandpaper would make it easy to press down evenly on it without getting your hands near the glue.

No liquid glue at all would have less mess, absolutely. My only worry about that is the cost. Good double-sided tape or transfer tape is not cheap. The reason I suggested carpet tape originally was because that was one of the cheaper solutions I could think of. How many of these are you looking to make? You can probably make a little spreadsheet to help the decision.
The glue gun route would require buying the glue gun and/or nozzle up front if you don’t have access to them, that’s maybe $100-150 worst case. Then you have expenses of just a couple cents per part for the glue.
Going self-adhesive or with double-sided tape has no cost for the tools, but the cost per unit for the adhesive goes up since you’re either buying double-side tape or having to pay extra for self-adhesive sandpaper.