bamacrazy 

Exactly what are the screw in grommets on bike frames called? I'm referring to the screws that mount water bottle cages and luggage racks. Also, can you order these in stainless?

curbtender

I'd call them mounting bolts.

Dan Burkhart 

The generic name is tubular threaded rivet. A couple of brand names are riv-nuts and nut-serts. They don't screw in, but rather are inserted and then compressed from behind like a blind rivet.
Riv-nuts are avilable in stainless or aluminum.

AEO

grommets are pieces that either reinforce a hole or protect something from sharp edges, kind of like a washer, but one piece will usually cover both sides.

the big difference is that they're never threaded. so calling the riv-nuts and brazeons 'grommets' is a misnomer.

tellyho

It depends on whether your frame is aluminum or steel. In an aluminum frame, the nuts are riveted in, in a steel frame, they're brazed-on.

Soil_Sampler

not always.

blamp28

For the OP:

Since we are trying to help here.

If you are referring to the threaded mounting points in your frame, they are called braze -ons by many as others have stated. If you are referring to the threaded fastener used to attach cages, racks etc. They are usually aluminum Socket Head Cap Screws or Button Head Cap Screws and are available also on stainless at any local bike shop or your local hardware store for less than a dollar.

bamacrazy 

Thanks for the help. I am talking about the threaded screws. This is for a steel frame Bianchi circa 1988. The caps have started to rust and I was hoping to replace them with stainless.

zzyzx_xyzzy

The actual screws are called screws

They're socket-head or button head cap screws, almost always 5x0.8mm threading, about 15mm length. Try your nearest fastener store.

bamacrazy 

The ones I needed were M5 Socket head screws. After 3 stops I was able to find them in stainless for 37 cents each. Thanks for all the help!

blamp28