Polishing concrete

[david s]

After my first attempt at grinding and polishing a concrete decorative arch using a 4" angle grinder and an orbital sander with wet and dry paper, I decided to lash out and purchase (Ebay), the correct machine. The first attempt turned out OK but took way too long. This machine makes the process way easier. The new machine is basically a 5" angle grinder with a water feed through the main shaft, variable speed control (a standard angle grinder is way too fast) and an electric safety cut out. It takes diamond pads that fit via velcro from 30 to 1500. I am extremely pleased with the results but still have to do the sealing and waxing. Big thanks to Stonecutter and Gulf for leading me onto this fascinating technique.Gulf and Stonecutters threads contain great details and pics.If looking for more info try "hand pressed concrete" or "concrete countertops"

[stonecutter]

Re: Polishing concrete

You will be pleased with that machine the more you use it too David. It will definitely elevate the look your pieces. Unless you want a very shiny surface, most of the time you can work from 100 - 800 grit...then the buff pad. And most diamond resin pads should be max rpm 3500. Metal vitrified are more aggressive.

EDIT: The RPM range for diamond resin pads is around 3000 - 5000 depending on what type (wet or dry ) and the brand. The 3500 rpm number is a safe average....and it is also the maximum for diamond profiler bits from Alpha

[david s]

Re: Polishing concrete

Thanks,
I feel the speed required is around halfway between it's max and min, is this correct, I really have no idea. When I ordered the machine I forgot that it would be a 110v. We operate on 240v so I had to also buy a step down power converter.No matter, I can now get more 110v tools. Could not find any small concrete polishing equip in Australia. No wonder we have no manufacturing sector left when you can't even obtain the right tools locally.

[Gulf]

Re: Polishing concrete

Looks great! to me David,
I have been doing "work a rounds" to keep from having to grind large aggregates. I have been using just wet sand paper. I will probably buy the right tools for any future projects. (like her kitchen counters ).

[stonecutter]

Re: Polishing concrete

Gulf, I have an Alpha VSP-120 for the last three years, and it's a great tool. Reasonably priced too.

[Gulf]

Re: Polishing concrete

Thanks for the tip Stonecutter,
There are several brands out there on the market. For someone like me who doesn't know one from the other, it is great to have a reference.

[stonecutter]

Re: Polishing concrete

No problem. There are a bunch of them out there, Makita, Metabo, Flex and Alpha are a few of the bigger names. I chose Alpha because they make great profile bits and have a solid reputation...which I can vouch for after what I have experienced.

[UtahBeehiver]

Re: Polishing concrete

Gulf,

Mine is a 5" Harden paid abt 165 for it most important is one with a gfi they actually sell them on the E site without gfi crazy you got a running stream of water during the whole process.

[RTflorida]

Re: Polishing concrete

Without hesitation I can say, stay away from the Secco polisher. I bought one about 4 yrs ago knowing I would only use it for a couple of projects, so price was everything. I got a whole kit with 10 or 12 pads for $149 from an ebay dealer. Very cheap water feed components that leak terribly and then rupture without warning. Plan on rebuilding immediately if you buy one of these. The deal killer is the sensitivity of the inline GFCI. You will receive a shock (many times) without warning thru the trigger and/or the water supply valve. The first few times scare the hell out of you, I thought I was about to be electrocuted. The first zap I actually dropped the tool and jumped back. Being an idiot who has never been scared by any tool, I proceeded. I came to realize the zap was about the equivelent of being zapped by a 120v light switch or outlet.
The dealer was pretty crappy, telling me it was due to the GFCI used and what I was experiencing was normal and the shock I was receiving is not considered harmful (and it wasn't)
Anyway, these things are still being sold on ebay as well as Amazon, I guess no one has died yet, but I have read many reviews stating the same experience.

Buyer beware, stick with the above mentioned brands.

RT

[david s]

Re: Polishing concrete

Without hesitation I can say, stay away from the Secco polisher. I bought one about 4 yrs ago knowing I would only use it for a couple of projects, so price was everything. I got a whole kit with 10 or 12 pads for $149 from an ebay dealer. Very cheap water feed components that leak terribly and then rupture without warning. Plan on rebuilding immediately if you buy one of these. The deal killer is the sensitivity of the inline GFCI. You will receive a shock (many times) without warning thru the trigger and/or the water supply valve. The first few times scare the hell out of you, I thought I was about to be electrocuted. The first zap I actually dropped the tool and jumped back. Being an idiot who has never been scared by any tool, I proceeded. I came to realize the zap was about the equivelent of being zapped by a 120v light switch or outlet.
The dealer was pretty crappy, telling me it was due to the GFCI used and what I was experiencing was normal and the shock I was receiving is not considered harmful (and it wasn't)
Anyway, these things are still being sold on ebay as well as Amazon, I guess no one has died yet, but I have read many reviews stating the same experience.

Buyer beware, stick with the above mentioned brands.

RT

Mine is from Pacific Rim Building supplies inc. I hope it isn't one of the dodgy ones.

[stonecutter]

Re: Polishing concrete

Thanks,
I feel the speed required is around halfway between it's max and min, is this correct, I really have no idea. When I ordered the machine I forgot that it would be a 110v. We operate on 240v so I had to also buy a step down power converter.No matter, I can now get more 110v tools. Could not find any small concrete polishing equip in Australia. No wonder we have no manufacturing sector left when you can't even obtain the right tools locally.

That may be OK David. My polisher has the variable speed dial numbered 1-5 (or 6..can't remember) and I don't use it higher than 3.5 for what I do, unless I am sharpening my carbide stone chisels.

[stonecutter]

Re: Polishing concrete

One more thing David and anyone interested. Get some diamond hand pads too. They are better for relieving edges, inverted surfaces ( after install, or keeps you from having to flip your piece) and sand small detail work (profiles). They are a compliment to the polisher and will help you turn out some clean work.

If you look at the pieces in my thread, you can see examples between the finishes using hand pads and a polisher. The watertable pieces on my wfo are all hand sanded to 600, were as the fp hearth is 3000, then buffed. I have yet to seal and wax the watertable, that will make them a bit more polished. The two finishes are like a honed vs polish.