The drill whines!
A customer brought in a Shimano Dura-Ace left crank where
the hex socket of the fixing bolt had been stripped,
and they were completely stumped.
Apparently a nearby shop turned them away.
I usually try to avoid rough work, but
since the hole was so stripped that a 5mm Allen key wouldn't grip at all,
I quickly decided to go with blowing off the bolt head.
As you can see, I haven't damaged the aluminum on the crank at all.
↑Like this
So I've blown off the bolt head, but the real problem is
how to recover this stub bolt portion
from the threaded hole on one side of the crank arm split.
So I was rummaging through my special tools box when
I found a tool specifically designed for recovering
the stub bolt portion after grinding off the head of a Hollowtech II fixing bolt.
You insert it between the split like this,
grip the bolt, and turn it.
You can probably advance about 60° in one motion.
Since the bolt head is gone, the clamping surface pressure is lost,
and there's almost no risk of the stub bolt being stuck from corrosion or seizing,
so it turns fairly easily as long as the tool grip shape is good.
The thickness of the tool's gripping portion is
deliberately thinned down to fit into the crank split.
Nice!
It's loosening, it's loosening.
Got it!
A customer brought in a Shimano Dura-Ace left crank where
the hex socket of the fixing bolt had been stripped,
and they were completely stumped.
Apparently a nearby shop turned them away.
I usually try to avoid rough work, but
since the hole was so stripped that a 5mm Allen key wouldn't grip at all,
I quickly decided to go with blowing off the bolt head.
As you can see, I haven't damaged the aluminum on the crank at all.
↑Like this
So I've blown off the bolt head, but the real problem is
how to recover this stub bolt portion
from the threaded hole on one side of the crank arm split.
So I was rummaging through my special tools box when
I found a tool specifically designed for recovering
the stub bolt portion after grinding off the head of a Hollowtech II fixing bolt.
You insert it between the split like this,
grip the bolt, and turn it.
You can probably advance about 60° in one motion.
Since the bolt head is gone, the clamping surface pressure is lost,
and there's almost no risk of the stub bolt being stuck from corrosion or seizing,
so it turns fairly easily as long as the tool grip shape is good.
The thickness of the tool's gripping portion is
deliberately thinned down to fit into the crank split.
Nice!
It's loosening, it's loosening.
Got it!