What kind of abrasive for smoothing concrete

[Chuck Kiser]

I'm going to use my Rotax to smooth some seams on a concrete floor.  [eek] What abrasive do you think would work the best? I'm thinking about Saphir, but I've never used that type.

Any thoughts?

Thanks.

 

[tbellemare]

Chuck:

I've never sanded concrete with it but I used my Rotex 150 to smooth out some really rough landscaping limestone with P24 Saphir and it worked great.

Tom

 

[AlexThePalex]

Sandpaper is not gonna work on concrete.

You'll need a concrete grinder like one of these

If you've got just a small job to do and you've got an angle grinder, then it's possible to get special discs for it too.

 

[WarnerConstCo.]

I have ground thin-set off the backs of tiles before with good sucess with saphir on my rotex.

Saphir is some heavy duty sandpaper.

I think there is some new paper coming out that is geared toward stone and the sort.

 

[AlexThePalex]

I have ground thin-set off the backs of tiles before with good sucess with saphir on my rotex.

Saphir is some heavy duty sandpaper.

I think there is some new paper coming out that is geared toward stone and the sort.

Thin-set tile mortar is not concrete. There's a huge difference. Tile mortar is pretty soft actually. Concrete is so much harder.

The paper you're referring to is Diamant, here in Europe it's already available. But it's not meant for a job like this. It starts at grit 500 and goes up to 3000. It is meant for the final finishing of very hard materials like natural stone. Not for grinding away concrete.

Anyway Chuck, if you want to try it out, slap a piece of 36 grit Saphir on your Rotex and let us know the result.

 

[Forrest Anderson]

Sandpaper is not gonna work on concrete.

It would seem that Festool has other ideas, as this extract from the UK 2010-11 catalogue proves...

Forrest

 

[Bob Marino]

I'm going to use my Rotax to smooth some seams on a concrete floor.  [eek] What abrasive do you think would work the best? I'm thinking about Saphir, but I've never used that type.

Any thoughts?

Thanks.

Chuck,

I have sanded concrete in my basement, used Saphir; as Forrest has pointed out, that's the recommended paper.

Bob

 

[WarnerConstCo.]

I'm going to use my Rotax to smooth some seams on a concrete floor.  [eek] What abrasive do you think would work the best? I'm thinking about Saphir, but I've never used that type.

Any thoughts?

Thanks.

Chuck,

I have sanded concrete in my basement, used Saphir; as Forrest has pointed out, that's the recommended paper.

Bob

[thanks]

 

[Chuck Kiser]

Thanks Guys,

Saphir it is. I'll take a few pics and let you know the results.

 

[AlexThePalex]

Sandpaper is not gonna work on concrete.

It would seem that Festool has other ideas, as this extract from the UK 2010-11 catalogue proves...

Forrest

Yeah, it says it right there. But does that mean sanding stuff that's ON the concrete or do they mean the CONCRETE ITSELF?

Chuck talks about smoothing seams in concrete. Maybe I've got this pictured all wrong but aren't those seams waste concrete extruding above the rest?

Btw, it also says in that picture you can sand metal. Now don't get me wrong, I appreciate the power of a Rotex with Saphir on it, but does that mean it can abrade the metal itself? Or just the stuff that's on it? I think the latter.

;D Anyway, Chuck will help me get rid of my delusions and report back to us. I'm curious how it goes. Which reminds me, I'm working on a concrete shed right now. I'll take the Rotex with me tomorrow and see what it does.
 

 

[tbellemare]

I'm reminded of the time when I was a kid and my Dad wanted to paint the garage floor (2-stall). He gave me an old, dilapidated chisel and told me to go over the entire area and remove anything stuck to the concrete.

Then he gave me a stone with a handle that was about 4" x 9" and had a few diagonal grooves across the bottom and told me to remove the surface. I ground the surface with that thing until it was a new surface, everywhere. It made significant dust and very smooth, clean concrete. I'm not sure what the stone was made of - I have it hanging in my garage today.

I'm just theorizing but I would think that if a skinny, energetic kid with a stone can do that, a Rotex can too. I'm not at all certain and am doubly uncertain what will happen to the abrasive. I'm tempted to try it myself just to see.

I have since used that stone to take a couple of high spots off concrete for various reasons. It still works and it's still a LOT of work...

Tom

 

[WarnerConstCo.]

I have sanded, or should I say grinded down a cast iron closet flange, with 36 grit saphir.  Took it down 3/4", with my RAS 115

I sharpen my lawn mower blades with 36 grit saphir on my RAS 115.

 

[AlexThePalex]

The RAS 115, with it's 3800 rpm versus the 650 of the Rotex, is already half-way of a grinder,

But maybe I'm misunderestimating the Rotex. Seems I got some experimenting to do.

 

[score0matic]

Sandpaper is not gonna work on concrete.

You'll need a concrete grinder like one of these

If you've got just a small job to do and you've got an angle grinder, then it's possible to get special discs for it too.

Alex
I had the Flex for about 5 years Loved it. the moter protection worked til it melted the circut board that held one of the brushes..  Now i Use HILTI DCG 500's
By the way a cup wheel on a dustless grinder works great to remove paint with out digging too much into the wood.
Craig

 

[WarnerConstCo.]

The RAS 115, with it's 3800 rpm versus the 650 of the Rotex, is already half-way of a grinder,

But maybe I'm misunderestimating the Rotex. Seems I got some experimenting to do.

I'm sorry, the first time I sharpened my lawn mower blades was with my Rotex.

I barley use the RAS 115 past speed setting 2 either.

On both sanders I used saphir, that is some heavy backed paper.  I think a rotex will do it, if the paper is up to the task.

 

[Nigel]

The angle grinder discs for concrete grinding that Alex mentioned work well and remove concrete very quickly but with tons of dust unfortunately.You could get one for less than a pack of saphir but the dust could be a problem.

 

[AlexThePalex]

Well, I tried it today, and I was totally unimpressed, just as I predicted. Now of course I don't know what quality of concrete people in other countries are used to, but the stuff we have here is way too hard. All I could do with Saphir 50 grit (was all I had) and the hard pad for the Rotex, is scratch the surface.

I sanded this small patch of the shed in rotary mode. The concrete was covered by paint (once) but most of the paint let loose when I scratched off the plants that grew against the walls. I don't know how you call those plants in English, but it's of the kind that climbs up a wall and attaches itself to it. This plant was particularly sticky and very hard to remove.

You can clearly see the seams made by the concrete casing. They were pretty small actually, but nevertheless pretty good visible.

After sanding for a while I was able to remove all the paint and the plant remains. But the seams were close to untouched. Just a tiny fraction, perhaps 1 or 2 mm was sanded away. They were still clearly visible.

The patch of 3 planks indicated by the red marker used up my entire sheet of Saphir. it was completely dull afterwards. I'd hate to think the enormous amount of paper needed when you really have to cover some surface.

A close up of a seam: despite it being just a very small protrusion, it was still there.

Anyway, perhaps other people can get other results. Please post the results.

 

[score0matic]

This will get you several hundred square ft of clean, smooth, sensuous  [scared] concrete

Craig

 

[Nigel]

I reckon you guys must have seriously soft materials in the States! [big grin]

 

[johnsonri]

Alex, thanks for posting your results there. I didn't think that the sander would do the job. Charimon has the right idea and kind of tool for the job. Will you post when you ultimately get the job done and indicate what you ended up using?

Thanks
Rey