Wet sanding?

Hi gents. I don't have much experience when it comes to sanding a blade. I've sanded some blades in the past and was happy with the results.
The other day I was at the hardware market near my home and I was going to pick up some wet dry sandpaper of various grit and one of the shops assistants was near me and I decided to hear his opinion on what sandpaper I should buy to restore a blade.
The grits he mentioned was not news to me - start at 200 and go all the way up to 1600 or 2000 - but what he said about how should I use the sandpaper was something that wanted to ask you. He told me to get wet-dry sandpaper, that's not news to me but, he told me that to sand metal I had to use some water, otherwise, it wouldn't work.
I've read the wiki and searched the forum for this type of sanding but found nothing.

Do you wet your blade or sandpaper before sanding? I only use water from time to time to clean the blade. And when using a grinder, isn't that dangerous to put some drops of water in the wheel? After all, it's an electrical device we're talking about...

Funny ~ I was doing a little sanding yesterday, and decided for the first time to wet the blade while I was rubbing. I used mineral oil, not water, and I have to say I was very pleased with the results. It seems to remove rust as it is leveling the metal. I was using 3,000 grit with mineral oil, and it left the blade fantastically smooth (I am working on a mirror finish, so any scratch will be immediately visible).

Question: does anyone use grits finer than 3,000? If so, where do you find sandpaper that fine?

I use wet-r-dry sandpaper but I do not use water, I use a little WD-40 when I get to 400 grit and above, and only after dry sanding at that grit first.... I would imagine any light machine oil would work if WD-40 or a similar spray is not available....

I have never heard of using water and buffers.... other than to cool the blade

Micro-mesh goes to 12000 grit

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Originally Posted by gssixgun

I use wet-r-dry sandpaper but I do not use water, I use a little WD-40 when I get to 400 grit and above, and only after dry sanding at that grit first.... I would imagine any light machine oil would work if WD-40 or a similar spray is not available....

I have never heard of using water and buffers.... other than to cool the blade

Micro-mesh goes to 12000 grit

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DOH !!!

So I would have been better off spraying a little WD40 while sanding all weekend !?!?!?!?!?!?!! :gaah:

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Originally Posted by igitur55

Funny ~ I was doing a little sanding yesterday, and decided for the first time to wet the blade while I was rubbing. I used mineral oil, not water, and I have to say I was very pleased with the results. It seems to remove rust as it is leveling the metal. I was using 3,000 grit with mineral oil, and it left the blade fantastically smooth (I am working on a mirror finish, so any scratch will be immediately visible).

Question: does anyone use grits finer than 3,000? If so, where do you find sandpaper that fine?

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You will find that any oil that is designed for penetrating rusted bolts ie: WD-40, PB Blaster, Kroil, and the like will work even better...

When you sand the blade dry, the steel particles and loose grits quickly clog the paper and it doesn’t cut as wall as fresh. Water washes the particles away and so the paper keeps cutting, but soon the paper wears out. Oil keeps the steel particles and the loose sandpaper grits in suspension (slurry), so the slurry and the paper and keeps cutting longer. You get a better finish because the slurry has loose grits that roll around, brake-up and get smaller while cutting the steel again and again, Either way water is better but oil is best when hand sanding, especially if you think water will rust your blade.

And if you are averse to the odor/toxicity/etc of WD40, 3 in 1, or other “machine” oils, my I suggest you go to the nearest pharmacy and pick up a bottle of Baby Oil (99% Mineral Oil). It’s just as good as any other industrial oil, non toxic, only need a few drops… and it smells good too. Now you won’t walk around smelling like a Refinery... I thank my wife for that one.

Smythe nailed it I'd say. Water will work fine– I've done it plenty. Oil seems better though.

I've always used water, but will be having a go with WD on the next one now & i'll see if it's better. I'd assumed the slurry created with the water was helping, but if the oil can suspend it more effectively that'd be great. I've not managed to find anything above 1200 grit here yet though.

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Originally Posted by Philadelph

Smythe nailed it I'd say. Water will work fine– I've done it plenty. Oil seems better though.

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Me too. Always used water with wet-n-dry paper. It works better, longer, and is more consistent across variations in the pressure you apply while sanding. Never heard of using oil. I'll have to try that.

What do you wet? anything and everything :). Usually just get some water on the grit side of the paper. It's going to bead up on the paper so it's not real exact. You could just sprinkle a few drops on the blade where you're sanding or you could keep a bowl of water next to you and just dip the paper in it occassionally as you work. Easy to tell when you need more water.

I use both water and oil on wet dry paper. I think that oil works better but I do not like the mess involved. A drop of dishwahing soap in a cup of water is a close second to oil.

Odorless mineral spirits, kerosene or oil all work well with most sandpapers that are designed to be used dry. The gold type papers (Mirka gold, 3M’s 216u) are available in low grits and work great on metal when used with a non water lubricant. (water ruins the glue holding the abrasive and the paper backing)

Sanding belts are available with the latest and greatest abrasives and are easy to order. A cut up belt will provide lots of paper for hand sanding. It is a good way to get lower grit and higher grit abrasives with quality abrasive.

Charlie

I do not use water, now. I use oil only with #2000, my last step before polishing cream compounds (for cars). I use sweet almond oil, just because I have it at home. It works well preventing rust (with water at #2000 after 30 mins I could see little yellow points appearing on the blade). After #2000+oil, I handsand with #2000+solid_soad, starting handsanding the soap (..not 30 mins! just few secs!!). This helps me to finish the work, since I can not find anything "smoother" thank #2000.