I deliberated for years over adding rivnuts for a water bottle cage to my Raleigh Gran Sport. The bike is no showboat, but I'm unaccustomed to drilling holes in 531 framesets. Well, I finally convinced myself it was the right thing to do, and after a couple test runs on a scrap piece of tubing, it was cake. The installation tool for rivnuts is costly for the occasional user, but I found the following method works very well. I ordered the rivnuts from McMaster Carr, pt. #95105A175.
Clearly there are frames I wouldn't drill, but for all the rest, this provides a nice and pretty simple alternative to clamps, handlebar cages or going thirsty, and does it with minimal damage to paint. I've read the horrors about rivnuts coming loose but my understanding is that most of those stories involve aluminum frames and probably aluminum rivnuts. I'm not expecting any problems from my steel/steel application.

Other than a drill, a small pilot bit, a 19/64" bit, and a little grease, this is what I used. That's an M5 bolt (I grabbed the clamp bolt from an unused brake lever), a 10 mm nut (you do NOT want the nut thread to fit the bolt) and a couple fender washers. The wrenches hopefully are obvious.

After applying some grease to both of the washers, the bits are assembled finger tight as shown prior to inserting the rivnut into the hole.

The 10mm wrench holds the nut while the bolt is turned to draw the rivnut tight. When it suddenly becomes more difficult to turn, it's time to stop.

The result is a well-crimped, solid attachment point for bottle cages. It might also prove useful for a chainguard-to-seat tube attachment. I wouldn't use them for smaller tubing, though - eg. seatstay rack attachment points.

What's your technique for drilling the holes on center?

I suppose I should say I made an elaborate jig and all that, but honestly I just taped a bottle cage on the frame, marked the locations and carefully drilled the pilot holes.

I measured a few frames with factory brazed bosses, and there didn't appear to be a standard location for bottle mounts on the downtube. You do need to be careful, though, to put the bottom hole high enough that you can get your drill in between the seat tube and downtube. My bottom hole is about 6" from the bottom bracket. A right-angle drill would be helpful but I don't own one. If you plan to do a lot of these you could cut off a drill bit and re-grind the edge; that would buy you some flexibility.

.. one more technique , a simple jig , drill a hole , or the 2 in the spacing you need
thru the corner of a piece of angle iron, drill press will get it straight .

then you can use the hand drill on the confined space in the frame.

That's essentially what the J.A.Stein bottle cage drilling jig is. I have one, and it works very well. A right angle drill is a handy thing to have too.

jiggy

Very nicely illustrated and described tutorial. Your M5 bolt, oversize nut and two wrenches can also be used to retighten an OEM Rivnut in a frame but loose.

Thank you. I ordered rivnuts, and am probably going to add a third water bottle cage to a more modern frame.

Thanks for your post. I need to replace a rivnut and this expedient method is what I'm going to use. I think If I was going to repair more rivnuts, I'd buy the tool for it. However, this one instance is the only one I've had ever.
Appreciate!

For anyone who might do more than a few rivnuts-

Cheap kits at Summit Racing, or Eastwood. I found Eastwood had the cheap prices for rivnuts in quantity. I bought packages for 5 and 6mm.

-SP