Which floor grinder to use?

[stang1]

Purchased 2 kits of tan epoxy coat from lowes. Planning on ginding to prep the floor and want to know which grinder: edco or blastrac! Thx.

 

[BigEd]

I'm sure you'll get better answers, but we rented a drum floor sander from Home Depot. It did a great job, but we did have to do some detail work on hands and knees around the edges and in the corners.

 

[munkey]

I rented the Edco and eventually had to rent the Bosch concrete resurfacer also. Yes, it ***** to do it by hand, but the Bosch worked soooo much better... I wish I had saved the rental fees and just bought the damn thing. Probably spent $200 on rentals and it sells for like $300 something. It works like a charm and gets the tight areas too.

Of course, the blastrac is a whole different class of machine, but I hear beginners can damage the floor pretty easily with a shotblaster if you aren't careful.

 

[PontiacFan]

Edco rotary type sander/grinder.

If the Blastrac is a shot-blast type, you might wanna stay away from that as a newbie.
As noted above by munkey, they are less forgiving if you start to mess up.

 

[stang1]

Thx for the advice. The blastrac is a 10'' rotating disc.

 

[Edger]

Grinding is not as easy as it seems. All single head and fixed two-head grinders will leave grinding marks and even some planetary (3 or 4 head) machines will too.

The rate of grinding is due to a mix of diamond segment bond vs the hardness of your floor, the size of the diamonds, the power and weight of the machine vs the diameter of the grinding wheels and the area of segments on the wheel(s).

If it grinds too quickly you will be left with lots of ring marks and the bigger machines will not do the edges - you will need a hand edger for those.

If it grinds too slowly you will get nowhere after the first 20 minutes. The trouble with rental shops is that they usually only provide one option. A contractor will have different discs for different floors and he will change them as soon as he knows what is happening, but you cannot do that normally with rental.

One guy might rent a grinder and find it perfect for his floor while another person will rent the same grinder and have nothing but trouble because his floor is different.

You can read more about diamonds and concrete hardness at http://www.situp.com.au/Grinding Hard Concrete.html

 

[munkey]

All single head and fixed two-head grinders will leave grinding marks (...) If it grinds too quickly you will be left with lots of ring marks

I can't argue with that -- I definitely had a number of ring marks. But, they were shallow enough that they are completely filled in or disguised by the epoxy. I could be wrong, I don't think it's particularly common to have a lot of visible markings when the coating is finished... especially if you flake the floor.

One guy might rent a grinder and find it perfect for his floor while another person will rent the same grinder and have nothing but trouble because his floor is different.

Good advice, I can definitely vouch for that. I had rented the machine for 2 days so I agreed to also do somebody else's garage while I had it. It ate away at my floor at a reasonable pace but barely scratched the other one. It is definitely an expensive hit or miss situation. It is also a very heavy and cumbersome machine to transfer into and out of your vehicle (I needed a helper.) You'll likely be fairly annoyed if you go to all the trouble and it doesn't do the job you wanted.