Saphir wearing out too quickly?

[Marlinspike]

I only get maybe 5 minutes out of Saphir 24 grit on my Makita version of the Rotex. Is this expected? Do i need to use less pressure or speed or something?

 

[Shane Holland]

[eek] [eek] [eek] [blink] [huh] [blink] [blink] [scared]

What are you sanding?

I've used Saphir to strip paint from metal and it was like brand new when I got done.

 

[Nat X]

I'm assuming it's just loading up because I've never seen any 24 grit paper wear down that quickly, even when sanding concrete.

 

[Xoncention]

24 grit is very course.  If there is no give in the material, like paint, rust etc being removed, then the heat build up with cause these large grit particles to detach from their bonded surface.  I have used 80 grit for paint removal on steel square posts, 200*200*3000 2 off and I stripped all the paint off and the single disk was hardly worn.  I stopped at an area when the metal was exposed then moved on.

 

[AlexThePalex]

When I use Saphir I mostly use 50 grit. The disk just goes on and on, spanning multiple jobs.

Not a fan of lower grit Saphir than 50, it is so course, you do a lot of damage to the surface beneath the paint.

 

[Marlinspike]

It's definitely not loading up. When it wears out, there is nothing visually I can see about it, but in use it stops removing material quickly (floor poly) and leaves behind a finish more like 180 grit.

 

[Cheese]

Are you using dust collection on the Makita?

 

[nickao]

It's definitely not loading up. When it wears out, there is nothing visually I can see about it, but in use it stops removing material quickly (floor poly) and leaves behind a finish more like 180 grit.

You are 100% correct, I use the 24 grit and the 36 grit get used up fairly quickly to an extent as well. The disc does not gum up or anything like that, it just stops taking off material at the same rate 5 minutes into it it. Showing a sheet of used disc paper will only show a disc that looks fine, it just doesn't remove material.I go through them  fast, way to fast. For the record they work better on metal than wood. Why?I have no idea. It must be from the way they make them I guess. It's just a fact I learned to live with and will jump to another manufacturer when I can for the lower grits.

As far as acting like a 180,  I dont know if I would go that far, but I hear you definitely.

 

[Marlinspike]

Are you using dust collection on the Makita?

Yes

Can you post a photo of one of the used discs? That poly can potentially melt and load.

I could, but you won't see anything. Looking at the discs side by side they look identical to me new vs old. I'll try lowing the speed, maybe it's the kind of thing where max speed works very quickly but doesn't last at all and a slower speed would work longer enough to make up for the slowness. I know Granat last plenty long on the tool though, while the stuff Makita sells for it is useless in under a minute.

 

[Cheese]

So if you take a fresh disc & a used disc and run then against the back of your hand, there will be a huge difference in feel?

 

[nickao]

Yes there is a difference. A new 24 grit is sharp like diamond and can almost cut you(it can cut you actually), after 5 minute I can use one as a back scratcher.

Looking at them they look the same, they just lose their cut.

 

[Marlinspike]

Exactly, in fact the fresh disc just grabs the back of my hand and won't move. The used disc is scratchy but slides along

 

[Cheese]

Well, Festool claims that the Saphir is a friable aluminum oxide product, however, both of your descriptions would say that the aluminum oxide they are using is NOT friable and it just acts like normal aluminum oxide...the sharp points just wear down to smooth rounded points.

Maybe a ceramic based product, such as 3M Cubitron would be better for your application. Cubitron is 3-5 times tougher than aluminum oxide and is also friable.
http://solutions.3m.com/wps/portal/3M/en_US/3MIndustrial/Abrasives/Products/~/3M-Cubitron-II-Hookit-Clean-Sanding-Paper-Disc-732U?N=7581643+3293218951&rt=rud
http://multimedia.3m.com/mws/media/...ilm-and-732u-paper-sanding-discs-flyerpdf.pdf