I have sheared two bolts in the rack mounts of my tricross, by the drop out. Clean break, with nothing protruding. How easy a job is it to drill these out? It’s not something I’ve done before – do you just take an electric drill to it with it leant up against a wall? Also, do the threads stand up to this drilling procedure OK or do you have to make new ones?

Happy to take it to the LBS but thought it worth asking if it was a simple job.

trick is keeping the frame still, the drill at 90 degrees to the bolt and the drill bit from skating around.

personally I’d want to clamp the frame in something and use a pillar drill to ensure it’s straight.

Look at using a stud extractor type thing as yu drill a smaller hole and won’t damage the threads int he frame.

risky – the problem is the bolt is harder than the frame.

To do it with a hand drill you need a steady hand – centre punch it and start with a small drill.

there is a fair chance of damaging the threads – but helicoils or tapping to the next size will probably repair them

Try an extractor or drill in from the back and the drill will go in the right direction to unscrew it

If you can see the back of the bolt (bolt hole is open) then try with a small drill bit (2-2.5mm) from the opposite side as the screwing in of the drill bit will be turning in the loosening direction for the broken bolt and as the drill bites the broken bit it should un-screw it for you.

By using a smaller drill than the bolt you should not touch the treads and you should not need to worry about re-dressing the them for the new bolt to fit in.

Also, use a centre punch to guide it, plece the dropout on something solid and clamp it so you’re not chasing it around and use a new, sharp drill bit to give yourself a fighting chance.

Lastly, if it’s a precious frame, get someone else (a pro) to do it so you have some comeback if it all goes badly wrong.

Thanks for the answers – I’ll give it a cautious attempt and see how it goes.
Is it not going to be difficult to drill from the back because the other side of the frame is in the way? Not visualising how you could get the drill to go in straight on.

Centre punch from the front, pilot drill with a smaller diameter then use a long series from the back and it might twist out anyway. Drilled out a seized gear cable adjuster in my tricross frame and couldn’t get it square so progressively drilled larger sizes until the remains pushed out. Fiddly!

Pop down your local screwfix and invest in a set of these. Saved the day on many occasion. Threads left intact.