Is a variable speed grinder essential?

[stonecutter]

Re: Is a variable speed grinder essential?

@Stonecutter, I didn't know it was possible to do this by hand! I'm casting in situ and intend floating some broken glass into the surface. My total surface area is about 3m^2. Is it really feasible to get a glassy sheen by hand? Is it going to take a ridiculous amount of time? Some areas will be difficult to access with the grinder. I'd prefer to do this be hand if it's a realistic approach? If doing it by hand what grits should I be buying ?

If you are seeding your pour with glass or aggregate, then I would recommend power tools. But to answer your question, yes, you can get a glass like surface with hand pads.

What grits you would need depend on how your concrete is troweled off, type of aggregate used, and what you want to see as a finished surface.

You can buy a variable speed grinder and dry polishing pads ( metal bond vitrified are good) for a reasonable amount of money (google). Use respiratory protection when you dry grind. Metal bond pads are aggressive and usually only go to 200 grit. From there you can get resin bond and higher grit. Keep in mind, you want to use resin bond at lower rmp, otherwise the pads can burn.

[deejayoh]

Re: Is a variable speed grinder essential?

My experience was that you run the speed up to where it feels like it is working, it's pretty easy to gauge.

FWIW, I didn't feel unsafe using the grinder. Rubber gloves +rubber boots + GFCI. Only popped the fuse once and I knew why.

[RichC]

Re: Is a variable speed grinder essential?

@Stonecutter, I didn't know it was possible to do this by hand! I'm casting in situ and intend floating some broken glass into the surface. My total surface area is about 3m^2. Is it really feasible to get a glassy sheen by hand? Is it going to take a ridiculous amount of time? Some areas will be difficult to access with the grinder. I'd prefer to do this be hand if it's a realistic approach? If doing it by hand what grits should I be buying ?

[stonecutter]

Re: Is a variable speed grinder essential?

You could get diamond hand pads instead of cobbling something together. I've used non- insulated tools for polishing stone and concrete, it works well enough, but I wont recommend it. It's dangerous, and an unnecessary risk...especially since this is a personal project where you don't have a deadline or a client to please, consider a safer route.

Diamond hand pads come in grits from 50- 3000, and they work great. I do have a vs wet polisher, but I use the pads just as much, if not more, because they can finish areas that the polisher can't.

[RichC]

Re: Is a variable speed grinder essential?

Thanks guys!thsts a much better solution for me. How precise does speed control need to be for concrete polishing? Do you just turn it down and judge by the sound if it if it's at 50% of max? Or do you need to be within specific speed ranges depending on pad grit?

Thanks

R

[deejayoh]

Re: Is a variable speed grinder essential?

you can get a router speed controller from Amazon for $18. I used this and it worked fine to control the speed of an electric motor. No reason to step up to a VS grinder. Actually, you are better off with cheapy since you're going to expose it to a lot of water. The speed controller also has a GFCI fuse in it, which is helpful when you're standing in a pool of water...

Amazon.com: SE Electronic Stepless Speed Controller: Health & Personal Care

[Gulf]

Re: Is a variable speed grinder essential?

Rich,
I've seen where some have added "variable speed rheostat controls" to their's.
My grinder is not variable speed, but it worked fine for me on my small project.

EDIT: I might better add that I have only used the upsided down method for pouring counters. Since this method already has, most of what is wanted to be seen at the surface, it is mostly polishing with the more finer grits. But, in my case at least, the cheap grinder worked just fine.

[RichC]

Hi guys, I'm having a hard time finding a variable speed grinder for reasonable money. I'm wondering, is it possible to polish concrete with a normal grinder? What's the downside of this and would it just require some additional care?

Thanks

R