Repair Shimano Crank/BB threads?

spikebike

I have a shimano XTR crank with the integrated bb axle.

My Shimano FC-M960 XTR Crank arm fixing bolt was lost, I replaced it with an offbrand part, and after a few years said part split along a thread around the middle of the threaded section. It was tough to remove the broken half of the part and I slightly damaged the threads. Here's a representative picture of the part that broke:
http://noblesports.com/index.php?l=product_detail&p=3273

The threads look good, and I can put a thin screwdriver in the thread and follow the thread in and out without it catching or getting lost as I cycle the crank. Alas, I can't get a new end cap on. I bought 2 new caps and I can't get either more than 2-3 threads in and gets stuck. Part of this is the limited amount of torque I can apply to the TL-FC16 tool. When forced I end up destroying the threads of end cap (which are softer than the threads on the bb axle.).

So I was hoping to find/buy/borrow either a tap or even just a steel bolt that matches the thread on the inside of the bb axle. One that matches the thread of the bb/crank arm fixing bolt, but is made of steel instead of plastic or aluminum. The LBS examined the BB, tried a new crank carm fixing, and said I should try to find a tap or steel bolt with the right specs.

Thus my question. What is the thread of the crank arm fixing bolt/Shimano XTR axle? I'm guessing it's a M19 diameter (19mm), but no idea on the specifications for the thread. Anyone?

Any other ideas on fixing it so I don't have to replace the crank?

mrmonkfinger

FWIW those bolts are not meant to be done up very tight at all

nicklouse

it is only a preload bolt. just get another and read the manual before fitting it again.
EG undo the pich bolts first.

sloppycowpat

if the threads are a bit ruff try inserting the new bolt half turn in then quarter turn out etc until it gos in again properly, this should help to 'clean' the threads

nicklouse

sloppycowpat wrote:

if the threads are a bit ruff try inserting the new bolt half turn in then quarter turn out etc until it gos in again properly, this should help to 'clean' the threads

except for the fact the preload bolt is softer than the axle so it would do the oposite.

Normally it feels rough when the clamp (pinch) bolts have been done up incorrectly. IE first.