The drill is screaming!
A customer came in with a Kuwahara Kevcel bike.
The screw hole that holds the cover on the back of the BB (bottom bracket) had gotten stripped,
and they asked if I could do something about it.
↑They brought it in with this M5 screw attached to the dedicated cover.
After putting the cover on, they'd wrapped it with clear packing tape,
which made sense because if you push the screw (without turning it) from this state—
↑this happens.
The threads are completely stripped.
↑With the M5 screw hole enlarged beyond its original size,
I decided to use a helicoil insert to restore it so we could use an M5 screw again.
I drilled a 5.2mm pilot hole for the M5 helicoil
and cut the helicoil thread.
I installed the M5 helicoil.
This is now the new M5 screw hole.
Once the screw engaged properly with the threads,
I did this bit of performance theater in front of the customer—
grabbed the screw with pliers and lifted the whole bike by it.
That's how solid it is now.
In reality, since it only holds the cover in place, there's not much force involved.
All done.
I switched to a truss head screw because
I wanted a wider bearing surface under the head without a washer,
and I wanted the screw head to sit flush with the cover.
I'm pretty sure the original fastener was also a truss screw, not a cap screw like the one at the beginning.
For more on helicoils, (→see here).
A customer came in with a Kuwahara Kevcel bike.
The screw hole that holds the cover on the back of the BB (bottom bracket) had gotten stripped,
and they asked if I could do something about it.
↑They brought it in with this M5 screw attached to the dedicated cover.
After putting the cover on, they'd wrapped it with clear packing tape,
which made sense because if you push the screw (without turning it) from this state—
↑this happens.
The threads are completely stripped.
↑With the M5 screw hole enlarged beyond its original size,
I decided to use a helicoil insert to restore it so we could use an M5 screw again.
I drilled a 5.2mm pilot hole for the M5 helicoil
and cut the helicoil thread.
I installed the M5 helicoil.
This is now the new M5 screw hole.
Once the screw engaged properly with the threads,
I did this bit of performance theater in front of the customer—
grabbed the screw with pliers and lifted the whole bike by it.
That's how solid it is now.
In reality, since it only holds the cover in place, there's not much force involved.
All done.
I switched to a truss head screw because
I wanted a wider bearing surface under the head without a washer,
and I wanted the screw head to sit flush with the cover.
I'm pretty sure the original fastener was also a truss screw, not a cap screw like the one at the beginning.
For more on helicoils, (→see here).