Tile – Cutting marble tile w/ an angle grinder

A diamond hole saw will do the job, use plenty of water and light pressure.

You will do better with a single hole, AFA breakage goes, compared to making 2 edge semi circles.

Update

If we are talking about a toilet flange, there are 2 methods, each with variations, depending on your equipment.

1. With a tile wet saw, raise and lower the blade such that you cut diameter lines edge to edge. Rotate the tile 10 degrees and repeat. Flip the tile over and repeat from below. Remove teeth with an angle grinder fitted with a diamond blade. If you are connected to a GFCI outlet, a helper can slowly spritz the cutting with a water bottle. It will keep the dust to a minimum. I would recommend a continuous edge (not segmented or stepped) diamond blade for this. The cheap table type tile wet saws actually excel for this cut, allowing fast and accurate cuts, all from below.
2. The whole cut can be made with an angle grinder setup described above, you just have to tip the blade at 45 to the surface of the tile and sneak up on the line from the inside of the desired cut out. With marble you have to go slow and minimize pressure. This method also works nicely for electrical boxes.

Electric angle grinders are very useful tools, they can also be extremely dangerous. First and foremost, select a tool with as many of the latest safety features as you can afford:

• an integral clutch that disengages the drive-line upon wheel bind
• a "slow-start" or "soft-start" feature
• NO "lock-on" button
• a "deadman" trigger or lever feature (shuts off if you let go)
• an easily adjustable guard (no tools required)
• auto-braking

Buy gloves, goggles and dust mask when you buy the tool

Amps indicate the power that the motor draws during use and generally indicates the size and power of the motor (higher is "better"). I personally think a well built tool with the features I want and which is comfortable for me to hold and use is more important than the amp rating. If you are routinely grinding and cutting thick heavy hard metal materials you might consider a bigger/more powerful machine.

Voltage should be whatever your household current is (220-240vt angle grinder would not be practical for home or general shop use, pretty much industrial only)