Helicoil... Update 17th Oct!... Need To Source Bolts

[Sponge]

'Afternoon guys,

just curious about the whole business of helicoiling. I've never done it before but looks like I'll need to. I searched previous threads on it, and they all offer the very vague amount of information. I want to get it right the first time around so as to not regret it in future. Perfectionism has its benefits you know

Anyways, to the point:

1. Mounts already tapped to M6, so all I need to do is screw the coil in with the tool right? I suppose it's a tight fit?

2. Any loctite necessary for the coil? Afterall... it's purpose is to stay in, but perhaps loctiting is a worthy extra safety measure? I have heard of helicoils pulling out you see....

3. What length coils do you use? I look on the internet and all the M5 ones are mostly 0.8cm, or 8mm. Which apparently is a little short to fit fully into the 4 bolt mounts. I've heard whispers that something like M5x10mm is the most ideal? I'm basically after whatever length fully inserts in, without any 'wiggle room' ontop or below.

I'm sure other people'd find this kind of specific info useful if ever they need coiling. Since the countless other topics seem to somehow miss these out!

Thanks !

Edited October 17, 2008 by Sponge

[Ash-Kennard]

pete wright set up a guide a while ago, but i cant find it, if anyone knows the one i mean, try and post it

[JonMack]

When you screw in a normal bolt i've heard it spreads the coils slightly, which is what helps keep it in. You don't need any loctite, they're not likely to come out.

Regarding the length of the insert, I just screwed mine in so it was about 1/2 threads below the top of the mount, then left it in.

Are you sure that you're talking about the length when you see M5x0.8 and M5x1.0? That last number is the thread pitch, not the length of the coil.

[Bionic Balls]

you can't use a standard m5 helicoil now that you've tapped it to m6 thread- that is slightly too large for the coil (13/64")...

just keep it m6 unless you really really need it done, in which case i think you'll need a specialist insert (EG: m8-m5?)

adam

[Sponge]

It was pre-tapped to M6 by the previous owner.

Surely it is possible still? I mean, how a helicoil works is that you get a tap included in the kit, which is designed to cut M6 threads into the balded/stripped hole (which was formerly filled with M5 threads), and then the helicoil screws in with use of the tool? Apparently having it tapped to M6 already, makes the helicoiling a lot easier since the tapping job is already sorted?

Unless i've got something horribly wrong...

Feel free to correct me!

[Bionic Balls]

m6 thread/tap is not the same as the tap required for an m5 helicoil insert...

taken me ages to find the numbers! an m5 helicoil needs a 13/64" (just under 5mm) hole and then tapping with a 10-24 thread...

whereas an m6 thread is a 5mm hole and an m6x1 thread...

IE: an m5 x0.8 helicoil (what you want) won't fit in the m6x1 thread..

just use a bigger bolt! not worth all this hassle..

[Luke Rainbird]

Are you sure that you're talking about the length when you see M5x0.8 and M5x1.0? That last number is the thread pitch, not the length of the coil.

Often coils are listed as M* x L, (* obviously depending on diameter and L being the coil length)

As has been stated, the thread won't be standard M6 pitch - though may be doable still - otherwise you'll need to helicoil it to M6 (assuming there's enough surrounding material)

[Dan6061]

I think the helicoil's sit in a 5.5mm hole, or something?

Definately smaller than 6mm anyway, so you could either get the holes filled, drill them, tap them, and helicoil them... or just use M6 bolts.

[Clownbike]

Hey Sponge

I myself have used a M5 hellicoil in a M6 size hole. The result was not bad but i only rode it for about 2/3 weeks. It did seem to hold under a lot of pressure. If you have M6 bolts i'd stick with them - If you do not have any i can throw some your way .

Next time you need to drill 5.5 then put in an M5 hellicoil.

BTW I'll get those pics asap!

Neil

EDIT - Pics in your email

Edited September 25, 2008 by Clownbike

[Al_Fel]

The helicoil kit I got came with a 5.2mm drill bit.

You might be able to screw a helicoil into the m6 threads but I doubt it would hold very well.

[Sponge]

The helicoil kit I got came with a 5.2mm drill bit.

You might be able to screw a helicoil into the m6 threads but I doubt it would hold very well.

Newbish question, but would it not work if i just epoxy resin'd or loctited/studlocked the helicoil inside the frame's holes? Or do helicoils work by expanding/unravelling inside the original alu threads?

if not, surely there must be other types of thread repair, like a simple solid M6 to M5 conversion thread piece... kinda like a modified grub screw if you get me?

[Jason222]

I used the tap that came with the m5 helicoil kit, and then I put an m6 bolt in, and it fit perfectly? I think the tap is actually a m6 tap

[Sam F]

I used the tap that came with the m5 helicoil kit, and then I put an m6 bolt in, and it fit perfectly? I think the tap is actually a m6 tap

Thats because they class the inserts as m5.. not the actual tap. I think?

[Sponge]

I think the point he was making was that the tap might be M6 instead of M5.5 or whatever? since... an M6 bolt fit, according to him?

I've got a few ideas two or three posts up, so please if anyone could correct me/tell me if it's workable/impossible, then tell me.

Cheers

[Bionic Balls]

Newbish question, but would it not work if i just epoxy resin'd or loctited/studlocked the helicoil inside the frame's holes? Or do helicoils work by expanding/unravelling inside the original alu threads?

if not, surely there must be other types of thread repair, like a simple solid M6 to M5 conversion thread piece... kinda like a modified grub screw if you get me?

pretty sure they expand once they're in...hence the special tool

get on google and look at inserts...like you say- they'res all sorts (but not m6-m5 as far as i know..too thin)

adam

[JonMack]

Could go M8>M5?

[Heatsink]

Newbish question, but would it not work if i just epoxy resin'd or loctited/studlocked the helicoil inside the frame's holes? Or do helicoils work by expanding/unravelling inside the original alu threads?

The Helicoils dig into the thread of the outer material. If these threads are Epoxy instead of alu, then the pull out strength will of course be much lower.

if not, surely there must be other types of thread repair, like a simple solid M6 to M5 conversion thread piece... kinda like a modified grub screw if you get me?

There is such an insert design: The "Keensert"

A "Keensert" - Solid barrel with thread outside & inside and 4 locking arms which you hammer down through the theads after it's screwed in

For the M5 size, the smallest outer thread I can find is M8:

Alcoa Website catalog

Just for comparison, here's the "Helicoil" insert (tradename) which is commonly used by Trials riders, generic name "Wire Thread Insert"

Wire Thread Insert - Like a coiled spring especially designed to mate with threads inside and out.

I hope this helps a bit! I have a helicoil kit around and will dig it out and have a look at the size of the tap which comes with it. If I have a stroke of inspiration to solve your problem then I'll pop another reply in

Steve

EDIT: The Technical info on my WTIs is here (PDF) They need a 5.2mm Dia hole to do their magic in (The same as Anal's set, and most probabily the same as other WTI sets out there)

[Luke Rainbird]

Could go M8>M5?

If there's enough surrounding material, it's the way to go - I've done it to 2 frames I've had and wouldn't hesitate to do it again if standard helicoiling wasn't an option

[Sponge]

Thanks very much Steve! that was a lot of help. The Keensert idea is the last resort I suppose.

As for helicoiling itself, I think someone else earlier above mentioned how they managed to fit an M6 bolt into a tapped mount (using the tap included in M5 helicoil kits), surely does this mean that M6 is in some way or form compatible? Perhaps a bit of blue loctite to fill any gaps? Would that work?

^Say that fails and the helicoil pulls out, I could always go to the option of M8--> M5 afterwards, right?

If anyone can find a smaller Keensert, like M7--->M5, or even M6--->M5, i'd greatly greatly appreciate it . So much so, I'll send out a pair of brand new Zoo pads to anyone who does

EDIT: just a quick question for Luke Rainbird, how much material was there once you drilled out and tapped to M8? Which frames were they too? Also, do you think loctiting/studlocking the Keensert in is a good idea?

Edited September 25, 2008 by Sponge

[Heatsink]

Thanks very much Steve! that was a lot of help. The Keensert idea is the last resort I suppose.

As for helicoiling itself, I think someone else earlier above mentioned how they managed to fit an M6 bolt into a tapped mount (using the tap included in M5 helicoil kits), surely does this mean that M6 is in some way or form compatible? Perhaps a bit of blue loctite to fill any gaps? Would that work?

^Say that fails and the helicoil pulls out, I could always go to the option of M8--> M5 afterwards, right?

All the solid info I've found on the WTIs says that you'll have a worrying insecure insert if you screw it into an oversize hole. Trying to fill the gaps with a weaker material isn't the way forward. I wouldn't advise it! If you have some inserts to hand then why not investigate & form an Engineering judgement for yourself.

If anyone can find a smaller Keensert, like M7--->M5, or even M6--->M5, i'd greatly greatly appreciate it . So much so, I'll send out a pair of brand new Zoo pads to anyone who does

They start at M8 is all I can find. Here's a UK supplier Speciality Fastners

EDIT: just a quick question for Luke Rainbird, how much material was there once you drilled out and tapped to M8? Which frames were they too? Also, do you think loctiting/studlocking the Keensert in is a good idea?

My Echo Control has M5 holes tapped into blocks which are 10mm square. So with an M8 hole tapped in it then that's 1mm wall thickness at the tips of the threads. I defer to Luke's first hand experiences on whether this is enough material! I suspect that he did the same on an Echo. I've noticed that the tapped holes on my Echo aren't actually in the centre of the blocks, maybe 0.5mm out vertically.

For questions about how to use Keenserts, check out the Tech info link here: June 2008 Catalog

Any road, the more people know about thread inserts the better. There's not much to it really, and you can't beat the manufacturer datasheets for the solid information to help you know when and how to use them. An excellent tool up the sleeve of any Mechanical Engineer

One thing to look out for - Keenserts are expensive! Definately give the Supplier listed above a ring to see what their prices are like.

Steve

[Luke Rainbird]

Yeah, I had it done on two '04 Echo Control frames and would happily claim they were the strongest brake mounts I've ever run on a frame

There was around 1mm of solid material all the way around the insert, which I wasn't too sure about at first, but after checking it all out and thinking long and hard I went ahead with it and certainly wouldn't look back

You could always knock up something just a touch larger than M6 to give yourself a little more surrounding material if you'd prefer/need to

The reason you won't find much smaller standard inner/outer pitch style inserts is due to the fact this'll lead to regions of very little material within the insert, making the stress distributions within irregular I would imagine (See Diagram)

You need to keep a tihck enough wall for this not to be much of an issue really

As you can see, the thinner the wall of the insert the closer the two threads are together, and the more likely this thin region is to become too small/impossible

A Helicoil style insert has the same pitch inside and out, so won't have this issue and is a coil sitting in it's own thread as opposed to a solid peice

[Sponge]

ah fair enough, thanks guys.

As for helicoiling itself, would inserting it into M6 work? Say, I loctited it, to tighten the space up? Or does the helicoil work by expanding/retracting like spring inside the alu?

[liam-pantera]

depending how good your engineering knolege is you could try this ,

get a m8 bolt and set it in a vice under a piller drill with a 4.5mm drill bit

center pop the m8 bolt so thast the drill bit will sit in the bolts thread

drill out the bolt making it hollow and then procede to putt a m5 thread in with a tap

then tap your damaged mount out to m8 thread and insert the hollow bolt with locktitght or a epoxy resin compound aplied to ensure the bolt wont work free.

if the bolt protrudesthen cut the bolt off with a angle frinder and retap the hole and that should be a permenent fix .

as well as using a piller drill you could use a horizontal lathe

[Al_Fel]

depending how good your engineering knolege is you could try this ,

get a m8 bolt and set it in a vice under a piller drill with a 4.5mm drill bit

center pop the m8 bolt so thast the drill bit will sit in the bolts thread

drill out the bolt making it hollow and then procede to putt a m5 thread in with a tap

then tap your damaged mount out to m8 thread and insert the hollow bolt with locktitght or a epoxy resin compound aplied to ensure the bolt wont work free.

if the bolt protrudesthen cut the bolt off with a angle frinder and retap the hole and that should be a permenent fix .

as well as using a piller drill you could use a horizontal lathe

I was just about to reply with a very similar solution.

Get an M6 alu bolt and glue it into your frame with whatever you think, Then grind the bolt flat. Get a proper helicoil kit and drill and tap it the proper way.

That probably wont work to be honest but its just a suggestion.

Maybe you should give screwing a helicoil into the threads you've got a go first?

[2sixstreet]

My two cents worth...

You have a frame tapped to M6 which is more than likely 1.0 Pitch (standard)

You want to go back to M5 which has a standard pitch of 0.8 (standard)

The M5 helicoil (named by internal thread) has to have an internal pitch of 0.8 to match the bolt

The external pitch has to match the internal pitch by design

So, you need to tap M6 x 0.8 to run a standard M5 helicoil. The M6 x 0.1 you have at the moment is not suitable.

Helicoils work by being compressed when they are being wound in. Once the tension is taken off they expand and lock in. Removing is possible but requires a bit more force and there is a special extractor tool available.

As has been mentioned and if there is enough material i'd go for M8 and then tap the internal back to M5. Those Keenserts look good too but have not used them.

Other methods

- 'cold welding' the holes with a filler rod. It can be used with butane, propane MAPP etc.

- Have it fully welded and re-tapped

- Theres a product called 'Metal Repair' which might work for a short time but I doubt it would be a long term solution. It's a paste you mix and once it's gone off you can work it (file, drill, tap etc)