Re-tapping a stripped 5/16" hole

[Deadeye]

I had to drill out a broken bolt. It didn't go easily. I used a 7mm bit and then re-tapped 5/16" BSF. The bolt is sloppy in the new hole - and the tap wasn't hard work as it is normally, so I suspect my hole is over-sized and I'll need to re-do it larger.

I don't think a 10mm bolt will work (it's one of the clamping bolts for a planer block and 10mm starts to make too much hole in the clamping bar); other suggestions?

Thanks as always

 

[MikeK]

Will a 5/16-inch BSF insert work?

https://www.amazon.co.uk/V-Coil-16-inch-BSF-Thread-Repair/dp/B00EO4O9AK

 

[MusicMan]

Helicoil insert. Easy to do, works perfectly, sometimes better than the original.
https://www.amazon.co.uk/V-Coil-16-inch-BSF-Thread-Repair/dp/B00EO4O9AKthough you might find it cheaper elsewhere now you know what to look for.

[edit] sorry, just seen MikeK posted this before me, so +1 for him.

 

[NickM]

Yes, helicoil should be a good solution. They work really well and you often end up with a stronger thread than the original.

 

[Deadeye]

Thanks all. Well I never! Not seen those before; brilliant. Thank you

 

[Deadeye]

Update - I bought a thread repair kit from Chronos. I admit to being a bit skeptical - but it's done, and it's absolutely brilliant! Thank you so much for the pointer, it's turned a headache into a success.