which grit for an Edco grinder?

[Parc Ferme]

Im renting a grinder this weekend to profile my concrete floor for epoxy. The rental house has 2 grits for the Edco. 8 and 24 grit available. Which would be better for my floor?
The surface of my floor is very smooth and has a dense machine trowl finish. I dont need to remove a lot of material since its smooth, just profile.

the rental guy told me the grinding media is 4 sided and if it is used wet it has to be kept wet or once it dries and is used again, it will be very brittle and just chip it self away. Any truth to that?

Thanks.

[Edger]

Use the 24 grit which is very coarse, the 8 grit will leave very ugly deep scratches that epoxy probably will not cover. I have never heard of 4 sided media, make sure you are getting diamond segments, it does not sound like it because 8 grit diamonds are expensive.

I have only used the carborundum blocks once and never again. Useless in my books.

[Parc Ferme]

Thanks, I will give the 24 grit a try.

[wmc-wood]

I have only used the Edco for my own floor but had a similar situation. My floor was flat but over polished in a few places and the edco seamed to almost float on the hard surface. A few very helpfully people offered suggestions and the following worked in the end. I bought a 7" diamond cup grinder head to get into the corners/edges and that is what i used to cut through the very hard dark areas of concrete. It took a bit of focus to grind and not dig into and leave gouges in the concrete. I then used the edco to go-over the entire area. I added a 40lbs bag on top of the Edco to help down pressure.
A few other important things:
A LOT of dust will be created, use a respirator, fan(if you can just blow it out), vacuum, hat and old clothes. you will want for a shower like never before!
Make sure you use a adequate sized grinder (I burned up a decent 5"one ).
the edco will even occasionally trip a 20 amp breaker.
I look forward to having a nice epoxy floor BUT the grinding part sucked!
good luck!

[Ultimate Floors by Rhino]

Originally Posted by wmc-wood

I have only used the Edco for my own floor but had a similar situation. My floor was flat but over polished in a few places and the edco seamed to almost float on the hard surface. A few very helpfully people offered suggestions and the following worked in the end. I bought a 7" diamond cup grinder head to get into the corners/edges and that is what i used to cut through the very hard dark areas of concrete. It took a bit of focus to grind and not dig into and leave gouges in the concrete. I then used the edco to go-over the entire area. I added a 40lbs bag on top of the Edco to help down pressure.
A few other important things:
A LOT of dust will be created, use a respirator, fan(if you can just blow it out), vacuum, hat and old clothes. you will want for a shower like never before!
Make sure you use a adequate sized grinder (I burned up a decent 5"one ).
the edco will even occasionally trip a 20 amp breaker.
I look forward to having a nice epoxy floor BUT the grinding part sucked!
good luck!

There would have very minimal dust if you used a dust collection vac you can rent with the grinder.

[71flh]

Funny. How coarse is whatever you plan to drag over the floor?

I'll imagine that whatever it is, its harder than the coating.

Steel wheel floor jack?

[wmc-wood]

AJ~
You are correct, on advice from someone that used an Edco machine, i was told to rent a large tubeaxial fan and not the vac. Hindsight I should have got both. Although the biggest source of dust was from the angle grinder cup and the fact that i was on my hands and knees put me closer to it. I tried to position my decent sized shop vac to catch the dust but it could not keep up. My concrete was so hard in one area that i spent 2/3 time on 40% of floor area, and that was using the diamond head to spead things up.
~Bill