el forestero

I cross threaded a 6 mm screw into a hole in my bike frame when trying to mount a bottle cage. Was barely able to get the screw out. The hole is now messed up such that it won't allow me to drive a screw in fully. The steel screw is fine, whereas the aluminum hole is chewed up inside.

Any suggestions for a fix? I don't have major power tools at home, just an impact driver. And I live in the middle of nowhere so no LBS or repair shop is gonna fix it for me.

Kovkov

Tamiya

Rootman

I'd get the right sized tap and use it very slowly and carefully to straighten out the threads as best you can. If it holds a screw then use it, otherwise put a few slivers of course steel wool in the hole. Since this is not a structural bolt and has another one in the cage to back it up, it might just work. A helicoil of that size is going to be tough to put in, there usually isn't much 'meat' there to hold it. Back the cage up with a clamp if in doubt.

Le Mechanic

You might try tapping/cleaning up the threads first. The tap size you need is 5mm x .08 If the threads are too far gone, you'll need to replace the rivnut. You don't necessarily need any power tools, but a dermel tool makes quick work of it.

Andrew R Stewart 

And others would never use a brittle tap to straighten threads. Talk about potentially jumping out of the pan and into the fire, if the tap should break. Taps remove material, that's their job and what they like to do. If the hole is miss aligned then use a bolt to straighten it, well greased bolt that's long enough to extend well out to see the miss alignment and top lever that back. Rivnuts are soft for a reason and their threads are easily molded with a harder bolt, for the better or worse Andy

Rootman

Break a tap in an aluminum frame? I guess it's possible, I've never broken a good tap in aluminum. I suppose if you were clumsy you could snap it off by pressing it sideways. A bolt could do it too but I'd rather chase the threads with a tap than force a greased bolt (screw actually) into it. A rivnut will work fine, if he wants to go to that expense.

Andrew R Stewart 

Sorry but I thought you references straightening the threads, not chasing them. Andy

sch

Standard bottle cage hole is 5mm screw with threads being 5Mx0.8. Are you sure it is 6mm screw? If it is threading is probably 6Mx1.0, but this is unlikely.
Dunnoh about web ordering in Japan or auto repair supplies, but taps for either of these should be in the 200-400 yen range. Then you need a tap holder
which would be in the 300-600 yen range. A drill chuck will work in a pinch but you really really don't want to go more than a few rpm for this and it would
be best to use a block of wood with a 5 or 6mm through hole in it 2-3 cm deep clamped over the hole you wish to tap to keep the tap normal to the hole.
It should take very little torque to re-thread Aluminum and it will be easy to remove so much metal from the damaged threads that you end up with a
useless hole which will need a new rivnut.

el forestero

Thanks for all the info and suggestions, folks. It's been a good start to my education on rivnuts, something I'd never heard of before.

My mistake: The rivnut takes a 5 mm screw, and that's what I was using when I cross threaded it.

I mounted the bottle cage onto the one good rivnut that remains and went for a ride. It turns out the base of the bottle cage has a protrusion that blocks the motion of the front derailleur when trying to shift to the smallest chain ring. The cage will need to be mounted higher on the seat tube to clear the derailleur, so even if I fix or replace the damaged rivnut I'll have to attach the cage to the frame some other way. For now going to look into clamps.

Thinking of plugging the damaged rivnut with one of these to help keep water out of the frame and prevent rust, but open to other ideas: https://www.amazon.co.jp/gp/product/B074TGRQ2R

Photos of the bottle cage are here: https://www.amazon.co.jp/gp/product/B004Y69QX8

jp911

Follow the steel bolt advice. A tap is designed to cut threads, not repair them. Ideally, a thread chaser would be used, but not easy to find...

Andrew R Stewart 

Would a more traditional wire structure (no plastic) cage provide clearance for your ft der? Would using a stand off between the cage and the boss provide the clearance?

Without seeing the situation it's hard to give more specific suggestions. But if the cage needs repositioning there are a lot of various cage attaching designs, some work better then others. The plastic and/or Velcro strap on ones tend to move about more. My decades old fall back is a cage with tabs and radiator hose clamps.

As far as covering the no longer used holes- Do what Click and Clack suggest for when your engine light stays on, a piece of electrical tape covering the offender. Andy

dsbrantjr

Cage mount alternatives
recklesscognition.wordpress.com/2009/01/13/methods-for-attaching-water-bottle-cages-without-screws-and-bosses/
Adding Water Bottle Cages to Bicycles without Braze

Dan Burkhart 

And don't drive like my brother.

el forestero

I ended up trying to fix the rivnut and succeeded. I grabbed its flange with needle nose pliers to keep the rivnut from turning and screwed a bolt into it using more force than usual to cut through the chewed up threads. That fixed the threads enough that a bolt screws in and out of the rivnut ok again. Probably not the recommended procedure, but it worked.

Then I followed the procedure in a number of youtube videos that show how to tighten a loose rivnut, and that worked as well.

Now that I have a functioning rivnut again, I'm thinking of going with this QR mount that will provide clearance between the bottle cage and FD: https://www.topeak.com/global/en/pro...8-qr-cagemount

Thanks for the suggestions and the heads up on the inspiring range of options. Helped point me in the right directions.

Andrew R Stewart 

I wasn't aware of this Topeak mounting/release device. This is the type of item every shop should have one on hand. It's what I call a "getting out of jail" device. It can make all the difference in solving a customer's problems quickly and without much cost.

What I note is that it places the cage somewhat higher/lower on the tube with it's offset, from the tube bosses. cage mounts. I have done much of this same relocating using hardware store Al 1/2" x 1/8" strip. Here's a shot of our tandem, after some braze ons changes and respray, that show the strips also angling the cages for easier access. Andy

el forestero

Those are some excellent custom mounts, Andy. Great to see what's possible with a bit of aluminum and some ingenuity.

RGMN

I usually use either 3mm or 6mm spacers to get clearance between the bottle cage and FD.

Andrew R Stewart 

If you like then cage mounts check out these two items. Andy

el forestero

Great idea. Gonna see if spacers will do the trick.

Nice work. I just happen to be looking for a way to mount a mirror too. My bike has straight handlebars but my mirror's attached to a short stem and a ball and socket joint with a range of motion that only works with drop bars, so I can't plug it directly into my bar ends as it was designed to be used. Was working on a far more primitive solution to mirror mounting than you have there. Gonna research what kind of aluminum pieces I can get online here.