Garage ReNew
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How do you stop the swirl marks (~1/32 inch deep) when hand grinding concrete? I can't seem to stop letting the diamond cup grinder dig into the concrete. Should I keep the floor wet? Thanks!
7 inch dewalt grinder
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OP
Garage ReNew
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Is it simply skill and practice?
matt_i
Well-known member
A 7" grinder (if you are using a disk that big) is a pretty badass roughing tool with a lot of weight to it.
A 4" might be a better choice.
Also, a segmented (diamond?) wheel might bet better than a cup (?) not sure exactly what you are using.
A 4" might be a better choice.
Also, a segmented (diamond?) wheel might bet better than a cup (?) not sure exactly what you are using.
jevoy
Well-known member
You can use a flapper wheel after to touch up the swirl marks.
OP
Garage ReNew
Member
I'm using a DeWalt Grinding Wheel, Diamond Cup, 7 In. Tearing the **** out of everything. Lots of shallow "kiss" marks. A full flake should cover them but it's just not professional. Not sure if I have it shimmed correctly either. All kinds of dust escaping from the hood. What a mess!
Slowgsr
Well-known member
I used a 5" cup wheel in a 4.5" grinder. You have to make sure you keep the cup wheel perfectly flat against the floor.
We're you planning on grinding your entire floor with a cup wheel? Newer concrete is also more prone to kiss marks I've found.
OP
Garage ReNew
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Yes. I did it one time using a buffer with diamond tabs. Epoxied the floor with **** stuff from home depot and then for practice I tore that out with the cup wheel. It took be about 4 hours...can't send a pic from this machine. The garage floor is 15 years old.
hh76
Well-known member
I had pretty much the same setup. Takes a little practice, but you have to really let the grinder float, and don't let it stop moving. might have helped as the cup wheel got worn a little. It will never be perfect, just not really the right tool for the job.
OP
Garage ReNew
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Thanks hh76. What is the "right" tool?
OP
Garage ReNew
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Thanks, Jevoy.
wssix99
Well-known member
If you are doing the entire floor, you will be glad you went out and rented a shotblaster: http://www.concretenetwork.com/surface-preparation-buyers-guide/shotblasters.html
I can't imagine grinding an entire floor with a hand-grinder... Particularly the larger 7" - they are beasts.
On my concrete house, we used the 7" wheels to tear up large thicknesses of materials. (Walls, parapets, etc.) I used a 4.5" diamond wheel/grinder to profile a few areas of my floor (1/4" and less) before epoxy and was able to control the marks and get a nice finish. (My coating company then came in with their shotblasters for the broader surface.)
OP
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NitroShark
Well-known member
I did 1685sq ft with a 7"grinder with no problems.
Does not sound like it's shimmed correctly, shim the wheel "in/up" more. Also be sure to get the Optional top Bail Handle for control.
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Garage ReNew
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I adjusted my grinder. Will try it tomorrow. Just ordered the correct vacuum. I have have a "system" similar to NitoShark.
hh76
Well-known member
Right tool is probably a rented floor polisher with a diamabrush pad. Check out the flooring section, and you will find dozens of pages of info about this process.
wssix99
Well-known member
That is really impressive!
It's hard to see in the pictures, but keep in mind that some roughness will help your epoxy adhere. For my flaked floor, the shot blasting created ridges 1/32"-1/16" in depth and it looks and is holding up great.
For my non-flake floor, the company I had doing the job F'd up and it looks like ****. As relations there blew up, they admitted the mistake - that the smooth epoxy should have gone down on a smooth floor. (I should have done Terazo for my interior floors and we'll be going that way when I can afford to tear up everything and renovate...)
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OP
Garage ReNew
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Thanks, wssix99! I'm going to "smooth out" some of the kisses this afternoon with my flap disk. I agree, the full flake application (next weekend) should cover these. Pics to follow!