Can I drill smaller holes in granite? I want to install aluminum shelves on a vertical backsplash behind the stove. I will need to drill 7 holes for screws and or mollies. If I can ascertain the studs I can use screws. Would there be an advantage of drilling a smaller hole in granite say 1/8" to 1/4"? Meaning less stress and risk of fracture? Could I use carbide or do I need diamond tip? I do have scrap to practice on.
Carbide works well on granite.
It's best if you can provide cooling by drilling under water. If you're stuck with vertical tiles, frequent squirting might keep the drill bit and granite reasonably cool.
For best results, when it comes to drilling into stone, always use diamond drill bits. Don't let the term diamond scare you away from buying one. They're readily available from such vendors as Amazon for much less than you might think, a 5 piece 5/32” – ½” is $8 there. As another user here posted, DO NOT use the hammer drill setting on your drill. Easy does it, with a water spray bottle if you can't continuously run water at the drill site. As for mollys, I think you'll get the best results using something like a Powers mini dropin internally threaded expansion anchor. They take a machine thread screw that you can cut to whatever length you might need.
depending on the weight loaded on the shelves and the thickness of the granite, drilling through the granite (and attaching the brackets or standards to wall framing) would produce the most stable and sturdy shelves. The wall anchors would work also, but using the wall framing is more reliable. Drill using a carbide bit slightly larger than the screw diameter. Carbide tipped bits last longer than masonry bits, but cost more. If there are many holes use carbide (they will also drill faster if the drill has an impact or hammer selection switch). If you find the bit spinning off the mark use a nail set (or masonry nail) to gently and softly tap a starting dimple for the bit. Drill at low/ slow RPM's to prolong carbide life. Heat will dull drill point. Spritz with aqua if needed. Retract bit occasionally when drilling to remove granite dust to facilitate drill speed. I'd just be sure that when you are tightening the shelves to the wall that you don't over torque the screws. If the granite is not supported (because the wall is bowed) or against the wall, it might crack from over driving the screw.
Diamond tip is the only way to go and yes you need to spray it with water while you drill it whatever you do do not use the hammer or impact function on your driver just let it nice and gently turn its way into the material you can run painters tape criss cross across the whole you're getting ready to drill sometimes that will prevent chipping on the surface. Going into studs is definitely your best bet there is a new type of toggle bolt now that goes in with a long plastic insert and then they break off and you can use them at different depths depending on how thick your granite is they are about a dollar a piece you can get boxes of 30 of them at Lowes I used them recently to put handicap rails up on some old thick ceramic tile they work wonderful and they can hold plenty of weight I have to agree with the one answer that says do not over tighten your fasteners but I definitely would go with the diamond bit and once again above all do not use the hammer function on your drill.