Bicycle Mechanics - Advice on retapping eyelet on sprocket side.

I've ruined the eyelet thread on my aluminium frame (Trek 8000 ZX series) on the sprocket side. There's no room to use a bolt+locking nut as suggested on other threads. I think I should to retap the eyelet, and I wish to make the repair myself.

I've read;
http://www.sheldonbrown.com/tooltips/taps.html
http://www.sheldonbrown.com/gloss_ta-o.html

but I'm not sure what tap to get, Sheldon satates that some of the information is obsolete. The eyelet was originally 5mm 0.8.

* Do you recommend I drill a non-metric hole (#9 or 13/64) and find a 6mm tap?

* Should the tap be of the 'taper' variety?

* Does anyone know of a small, affordable, and recommendable (electrician's?) tapping set suitable for 'everyday' use as well as bicycle maintenace.

* Finally, are there any special issues with tapping aluminium?

A million thanks in advance,
AR.

Should be no problem. I'd use a #9 drill. Use a taper or a bottom tap. Just make SURE you drill and tap strait.

A little WD-40 is a good lube for tapping aluminum. Not absolutely necessary but it doesn't hurt.

Try Enco for taps

http://www.use-enco.com/CGI/INSRHM

or MSC

http://www1.mscdirect.com/cgi/nnsrhm?KNC-T7L391316886

One alternative to drilling and tapping the hole for a larger bolt is to thread (or push through if the threads are really stripped) an M5x.8 bolt from the inside of the dropout toward the outside. Use a bolt with a button head or pan head so it has very little thickness on the inside of the dropout. File the head a bit thinner if needed. Then install your rack, fenders or whatever and use a nut on the outside of the bolt to fasten it in place.

That way the thickness inside the dropout is minimal and shouldn't interfer with the chain or small cog the way a nut on the inside would.

One alternative to drilling and tapping the hole for a larger bolt is to thread (or push through if the threads are really stripped) an M5x.8 bolt from the inside of the dropout toward the outside. Use a bolt with a button head or pan head so it has very little thickness on the inside of the dropout. File the head a bit thinner if needed. Then install your rack, fenders or whatever and use a nut on the outside of the bolt to fasten it in place.

That way the thickness inside the dropout is minimal and shouldn't interfer with the chain or small cog the way a nut on the inside would.

+1 :)

Thanks for the advice.

The outward pointing bolt wouldn't be terribly convenient because I attach my trailer via the eyelets, and getting a screwdriver in there every time...

Heli coil It will be stronger then the original threads and if you remove and reinstall the part alot in a
aluminum frame you may be better off using heli coils on all the frequently removed pieces!! Follow
the directions to the T and use the high strength lock tite on the heli coil. When you put a steel bolt
into a aluminum or anyother material frame You should always use silver antisieze to prevent
galvanic corrosion, A $3.95 tube of silver anti sieze will save countless headaches and money!!

Thanks for the advice.

The outward pointing bolt wouldn't be terribly convenient because I attach my trailer via the eyelets, and getting a screwdriver in there every time...

OK, can you point the bolt out and add a nut butted right up against the outside face of the dropout to hold it firmly in place? Then add the trailer hitch to the remaining bolt length and add a second nut outside of it.

IF you tap, I recommend finding the proper size tap drill & tap BEFORE you start.

ISTR that wax is used as a tap lube for AL???

It seems to me that a threaded aluminum hole is inappropriate for frequent attachment/removal. Add a dynamic load (as in a trailer) and I would think it would strip again in short order.
I'm not suggesting that you get a new (steel) frame or anything but It'd be nice to not have the same problem again, down the road, eh what?
Or maybe I'm not getting something.

Drill it out and put a steel sleeve in it and use the bolt from inside method as suggested by another poster

Hillrider: I'll seriously reconsider the inside-out bolt method. I might try and think of a way to modify the bolt head in such a way that the bolt doesn't rotate when the torque required to tighten a locking nut is exerted. Your extra nut suggestion would probably work but I don't have that much room to play around with on the outside. I expect people would scoff, but I might try and use 'cold weld' compound in the eyelet to fix the bolt.

toofastgt: I'll take a look at helicoils. Never heard of them until I found these forums. I'd have to tighten/untighten the bolt frequently, so I'm not sure the helicoil is the solution.

thechamp: The type of trailer hitch I made is very rigid and the load stripping the thread is not an issue; it probably exerts similar types of forces on the eyelet as does a loaded rack (i.e shearing forces). The thread was stripped initially by my manually overtightening the bolt. My next frame will probably be steel; a Gunnar Rock Tour.

Thanks for all the help.

Can't believe all this was a year ago.

Yesterday I was perusing the taps at the hardware store and bought a 1/4" tap and #7 drill bit (as the tap package instructed). Drilled hole, double-checked online for tapping instructions, tapped hole. Done in less than 10 minutes. Perfect fix.

Threads in aluminum SUCKS!

Tap it and install a threaded insert (Helicoil or other). Do them BOTH. Maybe I should say do them ALL, not just the one.

Threads in aluminum SUCKS!

I was rather surprised at how easy it was to cut the new thread. Fortunately it's only for holding the rack. The rack was on there for a year with only one leg and nothing bad happened to that eyelet. I'm sure it will be okay provided I don't severely overtighten it.

conclusion: despite the above proviso I'd still recommend tapping a new thread. At worst it brought the eyelet back to essentially its original working state.

One alternative to drilling and tapping the hole for a larger bolt is to thread (or push through if the threads are really stripped) an M5x.8 bolt from the inside of the dropout toward the outside. Use a bolt with a button head or pan head so it has very little thickness on the inside of the dropout. File the head a bit thinner if needed. Then install your rack, fenders or whatever and use a nut on the outside of the bolt to fasten it in place.

That way the thickness inside the dropout is minimal and shouldn't interfer with the chain or small cog the way a nut on the inside would.

I have done this with my Trek 7500FX which has an aluminum frame and I was mounting a rack for loaded touring. I ground the head of a stainless pan head screw (Phillips drive) to about 0.5 mm thick and screwed into place from the inside on the cassette side. The little tiny bit of the Phillips drive that was left helped to hold it still while I screwed the nut on tight.

I did this before the threads were stripped, thinking that the 40 lbs on the rack was going to wreck the threads if I didn't take some preventative measures.

Well, it held fine and 3 years later it's still there.