sandpaper for aluminum???

[fujimo]

anybody have any ide what might be the best sandpaper to sand ali down- that would fit on the drum sander- if there is even such a thing?
figured i might try and build some aluminum taper sleds- from some ali flat bar.

bad idea???
as apposed to having it milled!

[fujimo]

maybe i should just try some scrap ali- and see how it goes- i am sure it would have to be super small increments!

[kennym]

Slow and steady, prob .003 increments ti lyou figure it out. I'm guessing 60 grit or coarser so it doesn't get hot and wont plug as bad.  

[fujimo]

worth a shot, i still have and use your boo sleds- and they are still fine- just always concerned that i might wear them out- or take off tooo much one day- and have a double taper sled   :D   .
figure i could make the ali ones- as a master.

[Robertfishes]

I used to build screen rooms, carports, etc... with aluminum extrusions and roof panels. Never sanded it...But when cutting the extrusions with a 10" miter saw and a 10 tpi blade I would have to wax the  blade or spray it with WD-40 to keep the aluminum from melting and sticking to the teeth..

[fujimo]

mmmm ...good idea!
waxing might be a good option!
thanks mate!

[Robertfishes]

could you glue a 1/4" thick wood or actionboo overlay on top of the aluminum..then tape 2 tapers side by side onto the bottom..then run it thru your sander several passes..then remove tapers and then you have your sled?  or just use a thick piece of actionboo in place of the aluminum, much cheaper and easier to work with..

[Robertfishes]

I have cut 1/4" and 3/8" thick aluminum alloy plating with a skill saw and a thin plywood blade, as long as you keep blade lubricated it cuts well...i did that when i wanted to put a 50hp outboard engine on a jonboat rated for 35hp..and on my old grouper fishing boat, I put a 225hp on a boat rated for 175hp after I had new transom,floor and stringers installed.

[Troy D. Breeding]

Don't want to sound like I'm trying to pop your bubble, but Alum. flat bar is a bad idea for a sled.

As the ol' saying goes "been there, done that" and the flat bar will hold heat when sanding tapers. Over time it "will" warp.

I had that same idea several years ago and it turned out to be a waste of time and money.

If you want to use alum., use square edge tubing with a 1/4" wall and pay a machine shop to do the work for you. Not cheap, but way better and will last you a life time.

[fujimo]

'kay...roger that
thanks for the heads up    
 cheers

[Bowjunkie]

Troy, I have a two piece aluminum sled, hinged at one end and shimmed at the other for any degree of taper. It hasn't warped at all, but I surely don't use mine like you used yours.

That being said, I'm having a hard time wrapping my mind around the thought that the aluminum will get hot enough to warp. As I'm grinding, I have my hands on the sled as it's coming out the back of the sander and I feel no heat whatsoever in the aluminum. I think any heat would have a difficult time transferring from the wood into the aluminum since the anti skid material I have on there creates an air gap/insulator of sorts.

I can tell the way the two machined pieces of aluminum fit perfectly together with no shims installed that the top isn't warped at all, but I will keep an eye on it and report it here if anything moves at all. Thanks for the heads up.

Just curious, what grit paper did you have on your drum?

[Troy D. Breeding]

Yea, I guess I do use one a bit more than the average fellow.

The day I got mine I returned home and went right to work on over 200 pair of parallel lams. I didn't take time to put anything on it to help hold the lam in place like sandpaper. After running about 50 pieces I started noticing the sled was quite warm. After about a 100 it was hot.

I took my lunch break and when I started back I checked a couple lams and thickness wasn't even from end to end. It wasn't much, but when your trying to keep everything in a max +/- .001" and all of a sudden it changes to +/- .005" it will make you almost flip out.

I took a straight edge and place it on the grinding surface and it wasn't hard to see what had happened. The sled had bowed up in the middle causing the lams to be thinner in the middle than on the ends.

Since switching to the tubing I haven't seen that problem, but I did put the sandpaper on it before ever starting.

[Krasus]

silicon carbide sandpaper is good for softer metals such as aluminum and brass. When sanding metal, you should use water to cool down the metal surface and the abrasive. Although water will reduce the amount of dust and debris in the air, you'll have to wipe away the slurry on the surface of the metal that forms as you sand.

You can get silicon carbide paper in a waterproof paper,then you can cool with water and not worry about excessive heat build up.

[Crooked Stic]

Corian works really good for lam sleds.

[Roy from Pa]

Fujio boy, they sell aluminum oxide sandpaper.

[Krasus]

It's actually not.  It's best for hardwoods where you need a long lasting paper.

[Roy from Pa]

I'm betting WayneO will believe me..  

[LittleBen]

I think you may be overthinking it.

You don't need to taper the aluminum. Get a piece of Al bar stock of the length width and thickness you want, then just stick down a relatively thin tapered lam on top of it with carpet tape or something like spray adhesive. Run your material on top of that and you'll replicate the taper.

The thinner the glued/taped down lam the better, that way the pressure from the sanding drum will press it perfectly flat against the Al sled when you grind your material on top.

[LittleBen]

Granted I've never done any of those steps I suggested ... Just thinking out loud ....

[Roy from Pa]

That's zactly what I do Ben. Only my sled is 3/4" X 3" X 36" oak. Then I lay my tapered pattern on top of it then my lam on top of the pattern..