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Definitely a diamond bit for glass and ceramics. I finally bought a 1/2 diamond hole saw for around $20. After wearing out my arm and several masonry and/or carbide bits and ending up with ragged holes, I threw in the towel and found a place on line to buy a diamond drill. It was a joy to use.
Masonry drill bits are good for concrete and rock (get a hammer drill). Masonry and carbide bits can be found in most hardware stores. Diamond bits are a specialty and you will have to go elsewhere.
Check on line for diamond drill bits or hobby stores (stained glass area).
I love my Bad Dog Tools bits - they will drill anything. Great company, too. Their guarantee is "for-real". I sent in a broken 1/16" bit and also complained about the wobble in the quick change adapter - had replacements for both in 3 days -FREE!
Found them at The Woodworking Shows. Goggle both for more info.
It's been years, and we don't do this kind of stuff anymore (only stained glass, and don't have work area set up here yet), but...
Are you drilling into marble or granite? You can used diamond-tipped drill bits specifically made for marble/granite. They are not cheap, but depending on how many holes you are making, may save you $$ in the long run. If not doing that many, try the titanium bits at your local hardware store. Go slow, clean out holes frequently to avoid build-up of dust around bit, allow bit to cool more often.
CRL (C.R.Laurence) was supplier we used for glazier supplies. I haven't bought from them in years -- used to have $100 minimum order and had to have (resale permit) tax i.d. number. CRL stocks diamond-tipped drill bits specifically for marble/granite. You may notice that they have a much more "open" look to the grooves -- that allows debris to move out of the hole so that the bit stays cooler. This is similar to the "masonry bits" that you see for concrete. It will last longer if you pull the bit out and clean off the dust several times when making the hole. Remember when drilling into "harder" material to take it slower as it it also "harder" on your drill bits.
That type of bit can be used w/ glass drill (looks like drill press, but had tri-pod feet and is designed to be placed on top of sheet of glass to drill hole in it. Note: you need to keep drill bits cooled while drilling or you will ruin them. -- ditto for diamond "tube drills". You go slowwww, when cutting to not get break-out in back. There are special supplies for cutting holes into glass -- putty to make a "well" around hole to be drilled so that you can put a "coolant" in it to keep the bit cool. You can use the same technique on tiles before final installation, rather than cutting holes after install. If you don't have the heavy weighted rings with seals (like CRL sells) to hold coolant on surface, you can use plumber's putty (harder to clean off). You can get small quantities of the coolant from stained glass shops -- ask for the coolant for "glass grinders" (dilute as per instructions on bottle).
If they change their website, try main link below and follow links: http://www.crlaurence.com
>sealants and tools
>tools for cutting and drilling
>crl glass drilling tools and accessories
If you can't order from them, and you really want that type, you may be able to get a glass shop(window glass, not stained glass) in your area to either sell you one order one for you when they place an order.