When is the sandpaper used up?

[reible]

I guess I'm not sure how to address this issue but I'll have a go at it.

Sandpaper can fail in several ways.

If you happen to tear it then it might be used up for that particular use. It also might live on as smaller cut up pieces.

Sanding disk are often used up at the edges but the center may remain in an almost unused state. Again if you re-purpose them the sub set of the parts might be very useful.

You can also burn the paper, this happens if you force the operation and especially if it happening in a small area, say a corner of a board. If the area is small enough you may find the main part of the sandpaper still quite usable.

Another thing that can happen and has already been mentioned is the loading. If you can't get to the grit you can use it. Sometimes the material becomes so fixed to the paper that it is a lost cause to attempt to remove the loading. This is where the stick cleaners come in. There are other methods such as chemical cleaning methods that can be used, I personal can not attest to how well they work.

Some sand paper specially cheap ones will loose the binder and the grit goes with it. This can also happen if you fold or reduce the radius to much or the paper happens to fold or crease.

Some paper has softer abrasives which will dull, some will re-fracture giving new cutting edges and often become much less aggressive in the process giving you an equivalent of a finer grit as you work. If you wanted to have he heavier grit then I guess this could be termed as used up paper.

The secondary side of this is the backing. In a lot of cases the heavier the backing the better the paper performs. You will see things like "E" or "J" weight backing etc. A good place to have a look around might be Klingsport's at:
http://www.woodworkingshop.com

I could go on but I bet your tired of this post by now so bye....

Ed

[foxtrapper]

If this is true what good is the Abrasive Cleaning Stick that I waited 6 months for that was on b/o ?

Back when I was doing all that testing, we didn't use a cleaning stick. A cleaning stick certainly works. It gets the gum and residue out from in the nooks and crannies of the grit. That gum and residue causes the sandpaper to float over the work, keeping the sharp edges from cutting into the wood. The cleaning sticks don't sharpen the grit.

The 10 minutes until done was pretty much universal. Be it Norton, Klingspor, or any of the ones we were testing. Oh sure, you could still sand with the stuff 20 minutes later, but you were removing virtually nothing. As soon as you find yourself leaning on the paper or grinder disc or whatever, it's done. If you notice a big change when you switch to a new piece of paper, you've gone way past being done.

[charlese]

Back when I was doing all that testing, we didn't use a cleaning stick. A cleaning stick certainly works. It gets the gum and residue out from in the nooks and crannies of the grit. That gum and residue causes the sandpaper to float over the work, keeping the sharp edges from cutting into the wood. The cleaning sticks don't sharpen the grit.

The 10 minutes until done was pretty much universal. Be it Norton, Klingspor, or any of the ones we were testing. Oh sure, you could still sand with the stuff 20 minutes later, but you were removing virtually nothing. As soon as you find yourself leaning on the paper or grinder disc or whatever, it's done. If you notice a big change when you switch to a new piece of paper, you've gone way past being done.

Doesn't the 10 minute of 20 minute thing depend on quite a few variables? I'm thinking length of stroke (hand sanding) hardness of wood, moisture of wood, area being sanded (or size of the paper used), pressure used on the operation, to mention a few.

You mentioned that when we find ourselves leaning on the paper, this will tell us the paper is worn out. How much pressure did your tests use?

[navycop]

The 10 minutes until done was pretty much universal. Be it Norton, Klingspor, or any of the ones we were testing.

What about 3M paper? Is wet sanding better than dry sanding? Or can u even do wet sanding on wood?

[foxtrapper]

Doesn't the 10 minute of 20 minute thing depend on quite a few variables? I'm thinking length of stroke (hand sanding) hardness of wood, moisture of wood, area being sanded (or size of the paper used), pressure used on the operation, to mention a few.

You mentioned that when we find ourselves leaning on the paper, this will tell us the paper is worn out. How much pressure did your tests use?

Yep, there's a lot of variables that need to be constrained. Not hard to constrain them. Between robotics and set parameters and monitoring devices, you'd get pretty good comparative data. The testing had been ongoing for years when I was there, and I'm sure it's still going on to this day.

The part about leaning on it as it wore was subjective and hands-on personal, though everyone involved with sanding is familiar with it. It wasn't part of the qualitative and quantitative data sets. This is just where we'd be working it by hand and comparing how the various papers worked and felt to a human user, be it in power tools (belt sanders, rotary, etc), and even hand sanding just folding a piece over and rubbing it against something.

We did do mechanised tests evaluating the performance gain of pressure. It's not much. If the paper is fresh and sharp and unloaded, it will remove move, but it wears out much quicker. So the total quantity of material removed because of the pressure increase was a washout.

What about 3M paper? Is wet sanding better than dry sanding? Or can u even do wet sanding on wood?

We did no wet sanding tests while I was there. I don't remember reading through the files on it. Myself, I would be very uninclined to wet sand wood. Do not remember any companies paper standing out appreciably. That includes 3M. But the testing I did was years ago, 3M paper may well be the hot lick today.

[charlese]

Thank you, foxtrapper! Hopefully, your further explanation(s) will help convince some of us that applying pressure while sanding is a lost cause.
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navycop - I can't think of any advantage to wet sand wood - only disadvantages. Seems the wood would swell and fibers would be more shredded, rather than smoothed. Not to mention possible harm to joints (glue lines).

However, I do remember an "how to do it article" on finishing that recommended a steel wool rubbing on a wet finish to change a gloss finish to a semi-gloss or satin.

There is another article that recommends using wet-dry sandpaper with a soapy water solution for a gloss! The important part is - both of these "sandings" were done on a COMPLETELY DRY FINISH, not on bare wood! http://www.woodworkersjournal.com/Ezine ... _5893.aspx

[nuhobby]

Good questions and the answers are appropriate as well. I like using the Abrasive Cleaning Stick Item 753523 on all forms of sand paper Disks, Belts and even flat sand Paper. These sticks extend the life of abrasive paper many times. Well worth the price and they seem to last forever. fjimp

My wife is now a fan of this cleaning stick. She uses it for her fingernail & manicure implements.

MERRY CHRISTMAS!!