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Hey guys so I just welded up a table and now I am going to make a table top. So here is the problem. I welded the table up and looks square but is off about 2 degrees here and there from heat warpage. So I want to make a tabletop that is flush with the steel bar I have. Going for the modern look. I'm afraid that no matter how closely I measure the concrete will overhang in some spots. How hard will it be to grind down the sides of the table to match? Also is there a cheap way to smooth out the table top without having to spend a few hundred on wet sander and multiple special pads? I have a grinder and sander and different types of disks but no specialty concrete tools.

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You can always use a masonry grinding wheel and a level, but be warned, there will be a LOT of dust! You'll want to seal off the room from the rest of the house, open the windows, put fans in the windows, wear goggles and a respirator. They sell shrouds that you can hook up a shop vac to the grinder to get a good bit of the dust, but it's still bad. And at that point, it might take you 2 to 4 hours. I leveled some high spots on my basement floor and man, what a time waster! You may be happier if you rented something bigger than a grinder, or used something like below - the bonus being, if you used aggregate, it'll shine through after grinding.

You could also rig up a sled if you would like, where you attach something flat to the back of your grinder and then run it along something flat and level independent of the table surface, like below. Unfortunately, I don't think they make diamond cup bits for routers, but you might be able to use a diamond hole saw with a 1/4" shank if you want to use a router/sled method.

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  • Agree, dust will be a huge issue. In my experience, it would be nearly impossible to accurately control how much material you remove with an angle grinder and such a cup. It just chews through concrete soooo fast at that RPM. – bobfandango Oct 8 '14 at 23:00
  • Ill be doing this in my garage so dust wont be a huge issue. Can I use a sander if not a grinder? – John Dangerous Oct 9 '14 at 1:07
  • The dust-buddy.com, when connected to a shopvac, reduced the amount of dust to a much more managable amount. You can improve the polishing vs grinding action by wet-grinding and using the masonry grinding wheel rather than the diamond cup wheel -- I got a pretty nice polish on a part of sidewalk. While the result is likely to be good enough for a work table, you'll really want to rent a concrete polisher for something that gets shown to the guests. – gbronner Oct 9 '14 at 15:07
  • You could use water to keep the dust down. It'll reduce the wear on the grinding wheel too. Obviously, take appropriate care with regards to water and electric power tools... – John Oct 9 '14 at 18:36
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The classic way to get a great finish on a concrete tabletop with minimal tooling is to pour it (upside down) on a glass sheet. If your table is smaller than a patio door, you can generally find a free patio door that someone has removed if you look for a while on craigslist or other classified ad sources, or check at the local recycling center. The main trick (depending on size and thus weight) is getting it back upright afterwards.

This method does tend to assume that you are not trying for a "terrazzo" look to your tabletop (with things embedded in the concrete and the surface ground down to expose them) - if you want that, find a tool rental outfit that has terrazzo grinders for rent, and rent one. Though you may still want to start on a glass sheet so that the surface is flat and your grinding needs are minimized.

  • Thanks for the advice. I think the glass sheet is a good idea. I'm going to give that a shot – John Dangerous Oct 10 '14 at 18:26

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