sandpaper for aluminum???

[Mad Max]

Originally posted by 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?

When you are trying to grind the sleds that's when it gets hot and warp

aluminum transfers heat fast
sanding will create heat.

[fujimo]

thanks everybody---'cept Roy of course- hmmmph!!    

Ben an' Roy,  i think that is the plan- see, i am quite worried about our radically changing humidity here, and also a bit worried about screwing up one of my good sleds- maybe thats the trick- a good heavy duty ali flat bar, and a sled double sided taped to it.
thats what i am gonna do.
thanks
 see it just takes an outsider- (with some smarts- helps too) to find the solution.
cheers
wayne

[Bowjunkie]

Mark, yep that's true, I would expect that, but that's not what Troy said caused his to warp.

The machinist who surfaced mine said he had to be careful because the cutterhead can put too much heat into it as well.

[Roy from Pa]

Jeff, post some pictures of your sled for the guys. I've seen it when I was at your shop.

[Troy D. Breeding]

One thing I will add.

The surface on any alum bar or tube may look perfectly flat, but if you run it under a fixed dial gauge you will find out different. Both the flat bar and the tube sled I now use had to be surfaced by the machinist to make it a true level surface. Both had dips and rises in the surface that was as much as .005" off.

[mikkekeswick]

Agreed Troy. I've seen surface grinders at work on 'flat' surfaces!
If you're going to the effort of making a dead true sled I would get it machined.

[fujimo]

gotcha!