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I've picked up a 27"x27"x2" piece of marble countertop off the street. I'd like to clean it up and use it, but I'd also like to trim it down.

I don't mind doing it myself, but want to make sure I'm doing it right. I've seen posts saying a diamond blade for my circular saw will do the trick.

Am I correct that the following approaches are reasonable?

  1. Marble/masonry continuous rim diamond blade
  2. Multiple shallow passes
  3. A trickle of water from a hose (plus a GFCI outlet or extension cord)
  4. Protecting the surfaces of the slab from chip out with tape/foam board

Anything not right there? Anything I'm missing? Should I not attempt this?

Thanks!

Tim
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  • Is your cut edge going to be visible/touch-able? Your ideas are sound (but for the fact that you'll do harm to your circular saw), but they won't get you a nice finished edge. – Aloysius Defenestrate Apr 20 '20 at 18:53
  • what are you trying to cut? – DMoore Apr 20 '20 at 19:01
  • @AloysiusDefenestrate do you mean harm to my saw or the blade? Should I scrounge up a cheap circular saw I don't mind sacrificing? (I expect to have to do a lot of polishing, fwiw.) – Tim Apr 20 '20 at 19:10
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    @Tim -- the saw bearings suffer from both dry dust and slurry. They just aren't made for that kind of abuse. So, yes, I'd use a saw you aren't very fond of. (And the blade will probably survive a few more cuts like this, but they are consumables.) – Aloysius Defenestrate Apr 20 '20 at 21:54

2 Answers2

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I have cut one inch granite and it went very well with one exception to your list. Make the cut in a single pass or you will have lines on the cut face. You can use a good circular saw because the small water flow will stop essentially all dust; there will be some water spray that contains fine particles but no problem. I have cut cinder block dry and that needed a "sacrificial " circular saw. Breakout was not a problem when going slow at the end of cut. What I did for water was use a gallon bottle with a 1/4 vinyl (aquarium) hose with a clamp or valve for control; then you can make the mess anywhere.It requires little water and it will run down the cut groove to the blade.

blacksmith37
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  • I really suggest using duct tape in the middle of your cut line to reduce chipping and cracks on the top. – DMoore Apr 21 '20 at 20:08
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Marble is fairly easy, both to cut and to clean up after cutting (basically wet-sanding to remove marks) as it's a comparatively soft stone.

People do use water with saws not made to be used with water - I tend to think that's a bad idea, but you make your choices. Dust control is important for your breathing and your saw's bearings if using a power saw - depending on the cuts you actually need to make, a "grit-edge" hacksaw blade (manually driven) offers a low dust/noise/expense approach, or you work outside with a shop vac sucking up a much of the dust as possible, or you rent a wet saw for a few hours...

Personally, I have cut a lot of tiles (harder than marble) with a dry diamond blade in an angle grinder. My "nice" circular saw managed to die anyway (time for new brushes, OK! Wait, not the brushes - you want a new armature? Have you looked at the price of a whole new saw?) without being abused that way, (the angle grinder is still kicking) and my "new" circular saw came from Habitat for Humanity's "Re-Store" at a price were I'd not be so worried about replacing it if need be. You make your choices.

Ecnerwal
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