I want to cry - threaded bolt woes

[Mr Gear]

So on Sunday, I replaced the front brake caliper on my mountain bike, and bled it nicely. It was all going so well until I had to do up the caliper retaining bolt that screws into the fork leg. The final little twist of the ratchet and I felt the bolt go loose. Another turn, and I was sure the thread had gone!

Nightmare... it was the thread in the fork leg that had failed. What do I do?

I think the bolt is an M5. Can I get it bored out to take an M6 bolt? Can I get a helicoil insert so I can carry on using M5 bolts?

Both Evans Cycles and Cycle Surgery say I need to get new fork, but I won't take that as an answer, especially since that will cost me at least £200. I have a feeling they are offering this advice purely because they don't have the tools or knowledge to make the repair.

Where can I find an engineering firm that would take this on for me?

[47p2]

A picture of the damaged area would help

[Mr Gear]

47p2 said:

A picture of the damaged area would help

In all honesty, you can't see much. The damage is to the thread inside the fork leg.

If you look at this picture:
http://static.bike-components.de/cache/Rock-Shox-R...
you can see the lugs where the caliper attaches... the lower one of those is the one that is threaded.

[agentnomad]

As I read it 3 easy answers

Drill it out 5.1mm and buy a longer bolt and a nylock nut and bolt it back in place

Helicoil it and use a 5mm bolt is it is/was now

Buy a new set of forks

Other option not keen on it, drill and tap it out the next size up 6mm this weakens the surrounding area

If you are in the DN..... post code area I may have a 5mm helicoil and the tool to fit it.

It is easy to do if you can drill and tap a thread you can helicoil a new thread

http://www.machinemart.co.uk/shop/product/details/...

http://www.amazon.co.uk/Silverline-127589-0-8-Thre...

Edited by agentnomad on Monday 30th December 17:21

[agentnomad]

As I read it 3 easy answers

Drill it out 5.1mm and buy a longer bolt and a nylock nut and bolt it back in place

Helicoil it and use a 5mm bolt is it is/was now

Buy a new set of forks

Other option not keen on it, drill and tap it out the next size up 6mm this weakens the surrounding area

If you are in the DN..... post code area I may have a 5mm helicoil and the tool to fit it.

It is easy to do if you can drill and tap a thread you can helicoil a new thread

http://www.machinemart.co.uk/shop/product/details/...

http://www.amazon.co.uk/Silverline-127589-0-8-Thre...

Edited by agentnomad on Monday 30th December 17:56

[rustandoil]

Could you drill the lug through 5mm and use a longer bolt and a nut?

[47p2]

Reason for a picture was to assess whether there was enough metal round the hole to drill and fit a Helicoil

[WinstonWolf]

M5 helicoil will give you a steel thread which is stronger and avoid the need to drill the caliper, it's an easy job for an engineering shop.

[gazza285]

It's scrap, you had best send it to me for disposal.

[Ray Luxury-Yacht]

Can easily be repaired, don't suffer the worry-merchants.

Helicoils are usually pretty good - but my tried and tested methods for repairs are 'Wurth Time-Sert inserts'

Tested on racing motorcycles by me and my team - never had a failure yet!

[Justin S]

Buy a helicoil kit, thread will be stronger than the alloy one. They are also stainless inserts. Done a few and never had a failure yet.
Cheapy one here
http://www.ebay.co.uk/itm/like/190785574119?hlpht=...

[Mr Gear]

Thanks for all the replies guys, especially the links to the various repair kits. I'm not familiar with all the different brand names, so that has really given me something to work with.

Thanks also for the offer of the loan of the repair kit - although I'm not local to you the gesture is much appreciated.

If this is a reasonable job to undertake at home, I'll get one of these kits ordered, or is it best left to an engineering firm?

[Rolls]

M5 helicoil... I've done the same before!

[Justin S]

99.9% It will be an M6. The only M5's on a bike are bottle cages and some stem pinch bolts.

[agentnomad]

You could buy the helical kit and then take it to an engineering company and if it is a small one the fitter may let you watch/show you how to do the job it is easy but I am an engineer of 30 plus years That way you have the kit for the next one and an experienced fitter/engineer does the job for you.

Hopefully for beer money

[fausTVR]

As agentnomad says, go to a small local machine shop, take the bolt with you to check which thread it is, ask if they could do it for you, there and then for a tenner say. No need to buy your own kit. As said, the result will be stronger than original and be careful in future not to over torque ally' threads.

[Mr Gear]

Indeed, I just had an email back from a small engineering firm nearby who have said they can definitely do it for me and it will be "easy". So I have started today with lifted spirits!

Thanks again for the responses.

[Mr Gear]

Happy ending! These guys helicoiled both caliper bolts for just £20: http://www.precisionengineers.me.uk/

Brakes finally sorted!