Grinder: Handheld vs. Standup (Commercial)

[5Cent]

Finally got in to the new house, but can't decide on what to do for the grinder.

The rental place will rent out a standup/commercial size one with a 7" wheel, or they sell the 7" wheel for a handheld grinder.

The garage is only 440 sq ft. Anyone have any experience with the standup ones?

 

[dwilliams35]

Just get both. You'll need them both before it's over with.

 

[thegarageguy]

With the walk behind, make sure you get some weight and diamond inserts. Not stones or scarifyers.

The hand grinder would work well also, you'll just have to be on your knees and be careful not to swirl up your concrete. Since you are a DIY'r, the coating may not go on thick enough to hide the swirls of a hand held grinder.

With both try to use a dust shield and vac. Make sure to then vac up all the floor with a wand and maybe even mop it up after if you can. Its very important to pick up all the dust particles before applicating since this could be your first point of failure.

 

[5Cent]

Thanks for the info guys. I think I'm going to just buy the 7" wheel for the handgrinder so I can control the process better. Plus it gives me a nice close up view of whats happening at the surface since I'll be on my knees

 

[roger55]

The hand grinder would work well also, you'll just have to be on your knees and be careful not to swirl up your concrete. Since you are a DIY'r, the coating may not go on thick enough to hide the swirls of a hand held grinder.
/QUOTE]

Agree!
I am a DIY'r and just bought a 7" hand grinder, vacuum hood and diamond wheel thinking it wouldn't be too tough to do it this way.
WRONG!
I started out doing a test area which will be under cabinets and couldn't do it smooth. Plus, even with the hood, material was flying everywhere. I have given up on the grinding idea and will get some of the gel type etching solution. It's a new floor and fairly smooth anyway.
Oh well, I needed a new grinder anyway and the wheel might come in handy down the road for something else.
Live and learn.

 

[jcs_in_ky]

Has anyone tried to use one of the Bosch 1773AK concrete grinders?

 

[menz300]

The Bosch 1773AK is awesome for this. I have one and granted it ***** being on knees to do the prep but can do a typical 2 car garage in and hour and a half to 2 hours depending on the shape the floor was in. This is a great tool for this job and it pays for itself in no time.

 

[FL_Javelin]

I HIGHLY recomend the large standup grinder. I used that and I cant imagine doing it by hand. One big advantage of the big grinder is it has an attached vacuum, there is a lot of dust which can ruin an epoxy job. As noted, get a diamond grinder. I used a small palm grinder to hit the low spots and edges the big grinder missed

Here a pic of my wife using it. Took it away after she wasnt sweeping it.

 

[jcs_in_ky]

menz300, How does your Bosch grinder doing at picking up the dust if you use a decent sized shopvac with it? I've got a large shop to do, about 2400 square feet but I'm going to have to do it in about five sections, over a year so I thought I might buy the 1773AK rather than renting a larger unit. I know it's going to take a long time compared to a standup unit bot the closest place I can rent a larger grinder is over 100 miles from here one way so the trips to rent would cost me a lot of time and money. It's also hard for me to get a full day to devote to doing the grinding but lots of days I get an extra 30 or 40 minutes so that's another reason I was considering purchasing the smaller grinder ove renting. How many square feet would you say you've been able to grind before you have to change wheels on it?

 

['the epoxy floor guy']

If you are looking at doing a smaller job 500 sf or less, I would Purchase ( or you may have one) a good 4 1/2" surface grinder. Then you can purchase a dust muzzle at dustmuzzle,com for $25.

Then I would go to Ebay, purchase a TURBO style cupwheel. 4" or 4 1/2"

ToolAmerica (ebay store) has a GOOD selection of OK grade diamonds for a fair price.

Total invested ~ $200-$250 Plus you have a Surface grinder for other things.

a REGULAR shop vac WILL WORK, BUT, when dust starts to fill the room after a while, STOP, Empty your tank and TAP THE EXCESS DUST OFF your filters. BE VERY GENTLE. If you create a hole or make the seal break you will get fine dust into the motor of your vac and the results are NOT GOOD.

IF you have a larger job I would suggest the same Plan using a 7"/9" grinder *** 6000 RPM ONLY ***

Purchase a Similar TURBO style Cupwheel in 7"

These will grind the FASTEST and provided the Smoothest (user friendly) finish. NO OOPS!

Using this 'idea' will make your floor project turn out 300% better than just saying F' it and just acid etching.

YOU WILL NOT REGRET DOING IT THE RIGHT WAY

 

[roger55]

If you are looking at doing a smaller job 500 sf or less, I would Purchase ( or you may have one) a good 4 1/2" surface grinder. Then you can purchase a dust muzzle at dustmuzzle,com for $25.

Then I would go to Ebay, purchase a TURBO style cupwheel. 4" or 4 1/2"

ToolAmerica (ebay store) has a GOOD selection of OK grade diamonds for a fair price.

Total invested ~ $200-$250 Plus you have a Surface grinder for other things.

a REGULAR shop vac WILL WORK, BUT, when dust starts to fill the room after a while, STOP, Empty your tank and TAP THE EXCESS DUST OFF your filters. BE VERY GENTLE. If you create a hole or make the seal break you will get fine dust into the motor of your vac and the results are NOT GOOD.

IF you have a larger job I would suggest the same Plan using a 7"/9" grinder *** 6000 RPM ONLY ***

Purchase a Similar TURBO style Cupwheel in 7"

These will grind the FASTEST and provided the Smoothest (user friendly) finish. NO OOPS!

Using this 'idea' will make your floor project turn out 300% better than just saying F' it and just acid etching.

YOU WILL NOT REGRET DOING IT THE RIGHT WAY

Been there, done that.
Couldn't get it smooth that way. Dips, gouges, pits, valleys, mounds. I don't recommend using a hand-held grinder.

 

['the epoxy floor guy']

Been there, done that.
Couldn't get it smooth that way. Dips, gouges, pits, valleys, mounds. I don't recommend using a hand-held grinder.

Did you use a Cup wheel JUST like the one in the Pic??

Single and Double row cup wheels are NOTORIOUS for problems like you describe.

Another HUGE factor on whether a 'hand' grinder will work or not is how SOFT the concrete is.

SOFT concrete will grind INCREDIBLY fast.

A Tip on finding out (for reference) NOT 100% perfect but a good indicator.

the LIGHTER the color of the concrete GENERALLY the SOFTER the concrete.

IF you have soft concrete just plan on MOVING FAST! Like using a car buffer keep the unit moving left and right. It will grind MUCH smoother if you cover the areas MULTIPLE times back and forth, instead of working on specific area go past it and then back to it.

I am working on posting some Videos on YOUTUBE. IF you have an account SUBSCRIBE TO my COMING SOON VIDEOS:

I will try to address as many of these questions on my Videos.

 

[roger55]

Did you use a Cup wheel JUST like the one in the Pic??

Single and Double row cup wheels are NOTORIOUS for problems like you describe.

Another HUGE factor on whether a 'hand' grinder will work or not is how SOFT the concrete is.

SOFT concrete will grind INCREDIBLY fast.

Yes, I got the same cup (same company too) you have in the picture except I got the 7" version.

My concrete must be soft like you say as it ground down extremely fast.
I tried moving fast but still couldn't do it smooth.

I only ground an area that will be under cabinets for a test.
No way I will continue to grind. It will be acid etching for me.

 

[roger55]

You guys made me make another attempt at grinding.
Sorry for being so negative.
I think I have got things figured out.

See my update in this thread:
http://www.garagejournal.com/forum/showthread.php?p=296591#post296591

 

[5Cent]

Well I ended up buying a 4 1/2 " diamond wheel and I'm glad I did. The standup model would have been overkill for 440 sq ft. It would be quicker witha 7" wheel, but I am very happy with the finish. No vacuum hook up so man it's a mess