How Do You Know When to Replace Sandpaper?

[mac davis]

Was that a trick answer? Damn, I hate tests...

mac

Please remove splinters before emailing

[Andy Dingley]

About twice as often as ypou probably do already.

Top quality sandpaper, replaced when necessary, is a very cost- effective expense when sanding. Costs a bit more, works a great deal better.

On some sanders (esp. belt sanders) you can clean the sandpaper with a rubber stick, rather than needing to rerplace it. This is less necessary on ROs though.

[Joe]

lmfao! Just what I was thinking.

[Joe]

This thread reminds me of a conversation/disagreement that my Dad and I always have. He 'downgrades' sandpaper as it gets more use. 120 becomes

180, 180 becomes 220, etc.... My point is that you shouldn't do that, especially when final sanding (addressed elsewhere in this thread) because dull big rocks don't cut/sand the same as sharp small rocks. I *always* use a fresh sheet (disk) when final sanding, and change it often (about 10 minutes of use). My thought on lower grits is if you're spending a *lot* of time final sanding, you're probably not changing the paper on the lower grits often enough.

ymwv (probably)

Joe

[Jeff Gorman]

"Andy Dingley" wrote

Really just hitching onto Andy's posting, I wonder what actually happens when a coated abrasive paper apparently wears?

Some grits get detached.

The spaces between grits are filled with dust, thereby preventing the grits from working.

What is puzzling me is that I was taught that when grinding metals, abrasives work because the grits fracture in use, thereby presenting new sharp edges to the material. If they don't fracture the wheel doesn't cut and the job overheats.

Now wood generally seems relatively soft stuff - is it usually hard enough to fracture the abrasive grains? Perhaps mostly not, hence is most wear due to the two points above?

Jeff

[Leon]

With the old sand papers, "flint, IIRC " the fracturing was especially true. with Aluminum Oxide particles, the typical wood sand paper, the particles simply dull and become less effective.

[Otoe]

Thank you for the post. I learned something from it. You too Andy!

Otoe