Abrasive grit sizes

Tools, Techniques, and Reference Materials Tools
1

Something puzzles me:

I normally use wet or dry sandpaper in grits 320, 400, 600, 800, 1000, 1200, 1500, 2000. All are readily available.

When I get Flex-i-file sanding bands, they don’t even offer 400 grit, and start at 160, then go to 240. I’ve never used any thing coarser than 320 except on wood and metal. I consider 320 only for major shaping and stock removal. What on earth do people use those coarse grits for?

Most of the suppliers of sanding sticks start at 320, but go from that to 600.

I do a lot of sanding. Going from 320 to 600 is a ridiculous amount of work, it takes forever to get the scratches out. Most of the time, I start at 400, or even at 600. I probably use more 400 grit than any two other grits combined.

Why does almost no one supply sticks or film in 400 grit?

2

I get the impression that this is a historical thing in the abrasives industry - there are a set of standard grits / grades which most manufacturers seem to stick to. Just an opinion, but it seems to me that the “standards” have some pretty unhelpfully grit/grade holes in them.

Just to add confusion to this, I was looking thought the 3M products a few days ago, in specific at some of their microfine product - these are rated in micro as oppose to any sort of traditional grade or grit?

3

Industry standard grit sizes: 8, 10, 12, 14, 16, 20, 24, 30, 36, 46, 54, 60, 70, 80, 90, 100, 120, 150, 220, 240, 280, 320, 400, 600, 700, 900, 800, 1000, 1200, 1500, 2000.

So as you can see, there aren’t any significant holes. From a practical point of view, a set of 60, 80, 120, 240, 320, 400, 600, 800, 1000 will serve most needs up to microscopic work.

The abrasives are available. My question is: why don’t most of the hobby suppliers supply the most useful grit? Flex-i-file is particularly annoying—such a useful tool, with mostly useless abrasives!

To answer your question about microfine materials:

Microfine materials are defined as polishing, rather than abrasive. This is usually applied to materials of greater than 1000 grit, and are more commonly given in micron sizes, rather than grits.

4

I have always found the 400 > 600 gap a pain in the rear end, is this not where part of your problem area is?

5

Actually, no. It’s the 320—600 gap that irritates me. The step from 400 to 600 doesn’t seem (seam?) all that problematic.