cutting a marble countertop

[paul]

    my wife bought a new vanity/marble countertop......story of my life-she didnt like the sink it came with and bought a differant one....it just doesnt quite fit into the existing hole(less than a 1/4 inch needs to come out total)  what is the best way to trim out the hole?

[TerryLaskiwski]

Hi there Paul,

One way you could go about this is using an inexpensive 4" angle grinder equiped with a dry cut blade - your local home improvement store should have one - they are metal with diamond grit embeded into the rim, they usually run about $15-25 depending on the size you buy,  Mark probably has some on the site as well, but I couldn't find them.  Anyways trace out on your counter top opening what you want to remove, and then have a go at it with the grinder - since a 1/4" isn't that much to remove it shouldn't take that long. Just work at it cutting from the inside of the opening outwards making small slices.   And you'll probably want to do this outside - since it will make alot of dust 

Terry

[Mark D.]

STOP!
Are these straight cuts? Are they curved cuts? I need more info. You can saw cut or grind it into the size you desire, but make sure you are using the right tools for this job.
If it is truly marble and not granite, you need to use a blade that will not cause the marble to chip or shatter. Marble is MUCH more brittle than granite. Use an electroplated or brazed blade if possible. Wet cutting on marble is best. After the cut and assuming that the newly cut/ground edge is visible you will need to polish the stone.
Then a good sealer is a must.
Mark

[paul]

hey....i should have been more specific......it is marble       it is an oval opening.....the new sink goes into the hole but starts to hang up as it is lowered.....i just need to whittle away a little bit of the hole to make the sink drop all the way down......it is a drop-in sink with a 1/2 inch lip....hope that helps

[Mark D.]

Good! Now I can work 

You can either use a diamond blade to cut the hole larger or a grinsing cup, unless the radius of the curve is very small, like 3" or less, in which case you should use a grinding drum. I prefer the grinding cup as it is quick and your chipping will be minimal (which really is not important as it is a drop in sink). The diamond blade when it is cutting through can always catch a vein producing a  large crack, chip or other problem.
Try This:
http://www.defusco.com/5811-brazed-concave-cup-med-p-2007.html
This grinding cup will screw onto a grinder. It has a medium sized diamond grit so while it is still plenty aggressive it is not so aggressive as to rip out a vein. Realistically you could enlarge a 10" circle with this tool to a 12" circle in 20 minutes or less on 3/4" marble.

When finished, seal this with Hydrex to prevent the stone from getting etched by chemicals. This sealer is impregnating and will stain-proof your stone also.
http://www.defusco.com/tenax-impregnator-and-sealer-liter-p-1436.html

Mark