As title really. What is the best way to remove a (broken) heli-coil?

I have discovered one in my forks where the brake caliper attaches.

The reason I discovered it is because it snapped when I was adjusting the caliper. I was torqueing up the bolt and it went snap and when I removed it there was half a helicoil attached. This has been there since new which is a bit annoying as I am going to have to take the bike back to the LBS where I bought it and ask why there was a helicoil in my fork in the first place…. Bike is 10 months old. No doubt they’ll say I put it there but we’ll see….

Anyway what is the best (cheap) tool for the job…?

Ta

Can you see the other part of the helicoil?

Odd for a helicoil to snap halfway?

Could it be just a short helicoil?

If the bike shop won’t fix it then you can buy a removal tool but they’re a bit basic and can damage the thread more.

Just be sure to get the right size.

A lot of aluminium parts have helicoiled threads as standard as it prolongs the life of the thread and if done properly is often a more secure fastening. You can normally pick the leading edge out of the thread and get hold of it with a pair of long nose pliers, then unwind it in an anti-clockwise pulling motion. I would leave it to your LBS because unless you have another helicoil and an insertion tool handy there is no point in taking the old one out. The helicoil thread may also be damaged and may need re tapping which requires the helicoil tap.

Drill (or screw extractor?) + new Helicoil?

Wouldn’t surprise me if fork/bike manufacturers weren’t either repairing threads damaged on the production line with helicoils or even fitting them from new (if you’re drilling and tapping anyway adding an insert takes seconds, it’s just a different tap), the magnesium alloy is pretty soft.

Run a normal M6 tap into it, it normally picks up on the helicoil when you try to unscrew it, and removes it in the process.

Is it there as standard, rather than being part of a repair? The base metal is pretty soft fo likely needs some form of reinforcement.

Either way at 10 months old I’d suggest pursuing the warranty route.

It’s absolutely common to use helicoil inserts in aluminium and magnesium castings. When fitted correctly it’s considered the better solution. They get a bad rep because they’re often badly fitted to bodge a repair in an expensive car part to avoid replacing it.

The problem isn’t that a helicoil has been used. It is a problem in that it sounds like it wasn’t fitted correctly.

Hmm OK then. I’ll see if the LBS can sort it. I swapped the top and bottom bolts over and it has screwed up to the correct torque now without spinning so safe to ride. I’ll take it out tomorrow after my ride and have a closer look at it. It was fitted as standard from new as I’ve had no repairs done on it.

Helicoils in soft materials are often factory fit by decent manufacturers.

I was torqueing up the bolt and it went snap

Torque wrench or tighten by hand till you fart type torquing?

Torque wrench. I’m thinking it might be the internal thread though now rather than a heli-coil as it is quite pliable. It’s just teh way it gave way was odd. There was zero sign that it was cross threaded as it went in and in fact I hadn’t taken it all the way out – just loosened it so the caliper would move and I could centre it. I was tightening it back up and it just gave way and started spinning freely.

One of these torque wrenches in fact https://www.wiggle.co.uk/effetto-mariposa-giustaforza-ii-torque-wrench-bits-1

doing it up to 7Nm as specified in the Shimano manual.

Very carefully with a scriber and needle nose pliers.

Are helicoils steel? If so you could see if it’s thread damage/helicoil with a magnet?

Just pop a new helicoil in – it’s knackered now anyway

IME brake mounting bolts are often quite short and don’t extend far enough into the fork, so they are really easy to strip. Obviously, you do not want it to bottom out in the hole, but you want it to reach to within 5 mm or so when it’s tightened. I would try carefully screwing in a longer bolt to see how much thread is left at the bottom of the hole. If there’s more than 10 mm or so, you might be able to fit a longer bolt. In that case, start with a bolt that is too long and thread it in by hand until it bottoms out (with the brake caliper fitted). Then measure how much too long it is and cut it so it’s a couple of millimeters too short and fit a thick washer to make certain it doesn’t bottom out.

Also, if you can fit a 20 mm larger rotor, you could try cutting the head off a long bolt, so you just have a threaded stud (do this for both mounting bolts). You will need an adapter to fit the larger rotor, so thread the studs right into the fork and Loctite them in place. Use locknuts to mount the brake adapter and cut the studs so they just reach the top of the locknuts. Then you mount your caliper to the adapter. This way, when you need to adjust your caliper alignment, you are only working with the bolts that thread into the adapter, not the fork. It’s cheap and easy to replace the adapter if you strip a thread. Much more difficult if the threads in the fork get stripped.

Helicoils are almost always stainless steel. That photo above looks like the remains of a stripped alloy thread.

If the helicoil thread is stripped a tappex insert can be fitted if there is enough room. They are better than helicoils but harder to fit.

What brand of forks? That does not look like a bit of a Helicoil.

They are Suntour forks. My thinking now is that it’s stripped thread. It’s too soft to be a helicoil. I haven’t dismantled it again yet (job for this afternoon) but assuming the thread is now knacked is fitting a helicoil going to be the solution?

Also, if you can fit a 20 mm larger rotor, you could try cutting the head off a long bolt, so you just have a threaded stud (do this for both mounting bolts).

It already has a 203mm rotor on it (with an adapter). It does only seem to have stripped a bit of the thread though as I did manage to tighten it up again – I didn’t dare touch it after that as I wanted to ride this morning so I will take it apart now….

Are helicoils steel? If so you could see if it’s thread damage/helicoil with a magnet?

Good shout – I’ll try that too but I’m 90% sure it’s thread damage now.

^^ Good luck with sorting it mate.👍 I never knew there was potentially one fitted on new forks. Makes sense I suppose but news to me.

That said, if it’s alloy stripped I wonder if it’s worth taking back to lbs anyway? Mind you id possibly take it down the road to a place near me that does car restorations and see if they could fit a helicoil, one never fitted one before.

You will need to fit a helicoil now, and probably a longer bolt.

Good luck with sorting it mate.👍

Thanks.

So in terms of fitting a helicoil do I just buy an M6 helicoil kit given that it is/was an M6 bolt or do I need to size up?

M6 kit will be fine, an M8 would be bigger than the fork mount and the bolt wouldn’t fit the caliper.

Whereabouts are you, I have a kit with plenty of inserts if your near Bournemouth/Poole

Thanks @jimmy748 – I used to be from Winchester but I am waaaaaay oop north now! – cheers though. I’ll get an M6 kit… I’m gonna need the tool to hold the tap as well so I can screw it in I guess as none of the kits I have seen have it..

one of these

and also one of these I suppose in case I have to do any others..

Are you sure it’s M6??

Pretty sure…

https://si.shimano.com/api/publish/storage/pdf/en/ev/BR-MT420/EV-BR-MT420-4544A.pdf

What are these forks people have seen Helicoils in as standard?

And yes 100% it’s M6.

Oops. 🤦‍♂️

So it seems that when I dismantled the caliper fitting previously to bleed the brakes I swapped the bolts over by mistake and put the shorter one at the top. It tightened up OK when I put it back together but when I tightened it up this time it has stripped the top few mm of the thread as the bolt was too short to take the load. 🙁 This explains why when I put the correct bolt in the top it tightens up OK as there is still thread lower down. There seems to be less than a third of the thread missing when I look into the hole and measure it against the bolt so I am hoping 🤞 that I can leave it like this without fitting a helicoil as TBH I’m not looking forward to drilling the fork and then tapping it in case I get it all crooked. I don’t have a vice or a drill press so it would be a manual job with it on the bench.

Thoughts anyone?

You are cleaning out the hole more than drilling, unless your not completely inept, it would be hard to mess it up.

It is pretty straightforward if you follow the instructions and take your time. You need to decide what depth of thread you want, and this is usually expressed in relation to the diameter of the thread so 2D means 12mm of thread in the case of M6, 2.5D means 15mm and so on.

Done properly helicoils are really strong. You don’t need a bench drill. As Jimmy says the drill will barely touch the sides. It helps to use a bit of lube when running the tap in. Taps can be brittle so if it stops turning stop, as a broken tap is a b**** to remove.

I sometimes find I can’t break off the tang at the bottom of the thread but it’s no big deal in this sort of application.

Go for it, it’s a great skill to have..

I dis my first helicoil a few months back after a similar ham-fisted episode, and it’s pretty straightforward. Take it slow, and clean out the swarf thoroughly after drilling and after tapping.

2D means 12mm of thread in the case of M6, 2.5D means 15mm and so on.

💡 Ah! Makes sense. I need quite a long one then – probably 3D at least (I’ll measure how far the existing bolt goes in). I was wondering how that worked as all the kits I have seen come with very short thread inserts…

Go for it, it’s a great skill to have..

I dis my first helicoil a few months back after a similar ham-fisted episode, and it’s pretty straightforward. Take it slow, and clean out the swarf thoroughly after drilling and after tapping.

OK then, I might have a bash at it – thanks for the encouragement… 🙂

Any recommended places to get the parts or is Amazon as good a place as any…?

In my experience they are much of a muchness, but probably best avoid the very cheapest. Once you have the kit the coils themselves are dirt cheap..

Let us know how you get on!

Just me personally here but I’d leave it alone.

The rotor is pushing the caliper towards the fork rather than away and the amount of thread removed doesn’t look massive. I’d use thread lock (ok, I do that anyway) and keep an eye on it.

That’s just me though (also a helicoil virgin.)

I’ve not fitted a helicoil but…

be wary of buying the longest helicoil that you think you can – the tapping tool will not cut fully formed thread right to the very tip, so you will not have as much length as you think.

The common rule of thumb is that 2 x D of thread is as strong as the bolt, so you’re unlikely to need a full 3 x D unless you think that is compensating for a poor quality of connection.

FWIW we use helicoils in nearly all aluminium threads when we design/manufacture stuff, it’s going to be used by spanner wielding numpties and makes a much more robust bolted connection.

Helicoils are a pain to shorten unless you can cut them with a small cutting disc. They come in standard lengths that are based on their diameter so a 2D m6 helicoil will be 12mm long and a 1.5D will be 9mm long when inserted etc. Choose one that is slightly shorter than the web thickness. Make sure you fully remove the little snap off tang used for driving it in. It is a great skill to have if you do your own spannering 🔧.

be wary of buying the longest helicoil that you think you can – the tapping tool will not cut fully formed thread right to the very tip, so you will not have as much length as you think.

The common rule of thumb is that 2 x D of thread is as strong as the bolt, so you’re unlikely to need a full 3 x D unless you think that is compensating for a poor quality of connection.

Thanks – Ive ordered one of these HELICOIL® plus kit recoil M6 x1.0 thread repair 6mm insert tap drill Bollhoff | eBay

Comes with various lengths up to 2D

Loads of sound advice here. Thanks a lot. 🙂