Problem with 3M Micro-Abrasive Sheets

[KarlMaldensNose]

I've been adhering the various grits (15, 5 and 0.5 micrograms) to various substrates (mouse pad, basswood, leather strop, etc.) and they do a great job. PROBLEM is that they wear out after only a few minutes of passes. The 0.5 is okay, but that's just an assumption since you can't feel the grit when new anyway because it's so fine. But the 5 and 15 start off noticeably gritty/bumpy, then go smooth very quickly. I don't think I'm using too much pressure... not much more than the weight of the knife itself.

So what gives?

I think I've heard these sheets referred to as wet/dry paper. Does that mean I should be wetting them with water during use? I really don't know what wet/dry paper is.

Your help is greatly appreciated.

 

[richard j]

if it says wetordry on the back then you can put water on the paper to help it cut better and keep it from clogging up. it can be used dry but it works better wet at times.

 

[James_Terrio]

I use my wet-or-dry papers with plenty of water until the end of each grit cycle, when I think I've got it pretty even with that grit. Doing the final few passes with FRESH dry paper, and the blade cleaned off, seems to give the finest finish. I think it's because sanding wet develops a slurry, which cuts faster, but can leave slightly uneven scratch patterns.

Incidentally, you're right not to use too much pressure. If you have to bear down on the workpiece, go back to a coarser grit instead. It always pays to get your finish or edge as consistent as you can with each successive stone or paper before moving to a finer one.

I presume you're sharpening to a convex edge, since you're using soft substrates, right? Keep in mind that by the time you're down to those super-fine grits, you're pushing a very sharp edge into the paper and that's going to wear abrasive off much faster than if you were using it to hand-polish the flat of the blade. Good luck and have fun!

 

[thombrogan]

The 15 micron and 5 micron sheets are made with silicon carbide abrasive. It's a hard, sharp crystal, but it also has a tendency to fracture into smaller, sharper shards as you use it. The saving grace of the sheets is that a lot of the abrasive is embedded within the mylar film, so it will feel smoother to the touch, but well-supported particles are poking out from the film and still cutting quickly. The non-saving part is that the 15 micron film will wear out before the 5 micron film which will wear out before the 0.5 micron film.

I find the sheets last a little longer with light mineral oil (I use Ballistol; grown ups use honing oil), but usually use water or nothing at all as the mess made is more of a pain than the faster-cutting longer-lasting effect of using the oil.