icepick_trotsky 

The Allen fitting on my seat post binder bolt is stripped. What's my next move? It's the kind with a 5mm hex head on both sides. Only the drive side is stripped, but that's the one that matters.

Velognome 

drill it out

icepick_trotsky 

Just straight through? What size bit?

sloar 

Use one of those reverse drive bits that are made for stripped out screws.

RoadGuy

Use a new, sharp, reverse-threaded (if you can find one) bit made specifically for drilling metal. The largest size that will fit down into the ruined hex shaped without jamming into the sides of the hole. Use oil, with light pressure.

You only want to drill down to the bottom of the head of the bolt to break the head of the bolt loose from the threaded portion. Once the head of the bolt comes loose, you will be able to push the threaded portion of the bolt out with the nut.

This is basically the same process you use to remove pop-rivets, in case you have done that before.

sloar 

they work..

Soody

If you've got spare imperial keys lying around, try hammering the slightly larger size in?

BradH

Find a torx bit that is a tight fit and tap it in with a hammer. It's worked for me quite a few times but if the bolt is really bad drilling always works.

J T CUNNINGHAM

Because an Allen (hex-head) bolt is harder than a grade 5, I would first use an abrasive point to round-out the internal flats.

Not following the above and while especially using a 135 degree split-point drill bit, you may just find that you have destroyed the bit,

the reason being that the special configuration of the split point tends to require support. I would also recommend the purchase of a set of

Stubby, aka Machine Screw, 135 degree split-point drills, as drill length is usually not required but drill stamina at the point is always of main concern.

Again re split-point drill bits, take note that they require no centre-punching acting as a guide; they being their own, in that they immediately bite into the parent

metal; the conventional method causing them to hang-up on the centre-punched parent metal's displacement.

As usual, lots of high quality drill lube, medium RPM, heavy pressure. Why heavy pressure? you want to cut the parent metal; not polish it!


Regards,
J T

Lascauxcaveman 

And if you have a bench grinder, you can taper the business end of the hex wrench just a little so it will tap in easier. I've done this on stripped 6mm stem bolts twice. And hex wrenches are pretty cheap, so I don't mind messing them up.

3alarmer 

.
...they're not all keyed, and if yours is not it would be easier to go at it from the other side.


However, given the laws of bicycle repair, yours is probly keyed. You'll know pretty quickly.
But it would have to be one of the sort that has a hex on both sides, and lots of the newer ones don't.

icepick_trotsky 

I ended up hammering in a star shaped hex drill bit that was slightly larger than the hole, then turning that with a crescent wrench. Worked beautifully! Thanks all.