[Closed] removing a sheared hex bit

Cut the seatpost clamp off

the seatpost clamp is an insert into the seat tube @murray, with the grub screw piercing the seat tube and pushing against that metal plate on the clamp

That sounds hard, cobalt drill bit perhaps to drill a pilot hole than left hand drill?

This kind of integrated seat clamp?

yep, that's the one @bigyan

LBS is about to try the cobalt drill bit approach @murray

My stock answer- Dremel a slot?

Mig a bolt to it?

a cobaltdrill will go through that no bother.

I'd be tempted to try buzzing it with a blunt masonry but on hammer first though

Is this one of those situations where you are supposed to hammer a torx fitting into the fouled bolt head?

Cut through the exposed bit of thread with a multitool or junior hacksaw blade.

I don't think many people have actually read the problem:-D

There is a bit of allen key stuck in the grub screw with nothing projecting out!

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"No, but between the two “halves” of the clamp is a small gap where the the clamp bolt is partially exposed."

Doesn't look like there is... Looks to be a very shitty design/solution to a problem that didn't exist...

I’d be tempted to try and free off the remains of the bit with a jewellers screwdriver or similar. If it snapped when you were trying to undo it, then presumably you need to try to tap it in a clockwise direction to free it off. Drilling would be a last resort for me, as then you’ve got the problem of getting the remains of the bolt out too.

Can you leave it in place and just buy longer or shorter cranks instead?

A Hex tool will be hard, so you might not have luck drilling a pilot hole in the stuck piece, then using an extraction bit, but that's what I'd try first.

Try adding heat? Soak in WD40?

Then I'd try finding someone with a welder - either might get the bit out or you might get the whole bolt out.

If you have a chisel, screwdriver or something pointy I'd also be tempted to just start hitting it to try and get it to turn or to loosen the stuck bit.

Good luck and report back!

No, but between the two “halves” of the clamp is a small gap where the the clamp bolt is partially exposed.”

Doesn’t look like there is… Looks to be a very shitty design/solution to a problem that didn’t exist…

Yeah, my bad, I didn’t notice the pics and that it was a posh bike.

A Hex tool will be hard, so you might not have luck drilling a pilot hole in the stuck piece, then using an extraction bit, but that’s what I’d try first.

Thats not my experience, hex bits I've cut and adapted no bother with files and hacksaws which probably why its no lammed in, its been smooshed out and created an interference fit.

Which is why hex bits don't go anywhere near my bikes or anything with torque over finder tight.

Is the tapped portion of the hole exposed, ie can you see the non- head end of the bolt, the end youd start a nut on?
If so, you can drill through from the non head end, and the bit might catch and spin it out of the thread. This will push the bolt anti clockwise and back it out of the hole. Only attempt this if youre confident that the you can drill pretty much dead central on the bolt end and bear in mind if the drill wanders you might trash your frame.
The bit will take the path of least resistance so if it isnt on centre it will want to burrow into the (presumably) softer wall of the frame.

*make sure the drill bit is smaller than the tapping hole or else youll drill the threads out.

Can you tap the sheared hex (gently) anti clockwise with a screwdriver or chisel? If you can do this and not cause a burr on the bolt socket, you might relieve the tension on the hex and be able to pull it out with a strong magnet . Might only wrk if the bolt socket is bigger than the hex bit though, ie that any attemots you have made so far havent peened the edge of the socket over and basically trapped the hex inside the socket.

@joshvegas been boozing already?

Thats not my experience, hex bits I’ve cut and adapted no bother with files and hacksaws which probably why its no lammed

in, its been smooshed out and created an interference fit.

Which is why hex bits don’t go anywhere near my bikes or anything with torque over finder tight.

I wouldn't try to drill it.  I would get something welded to the bolt head.  The heat will help loosen it and it gives you something to remove it with

What about the heat Vs carbon

If it's not a dropper, cut the post out and hope it relieves tension so you can undo the bolt with the broken bit in it?

Or how about getting some proper industrial component epoxy and gluing the broken bit back onto the stub, glue it to the bolt too.

Or both...

an update...

LBS cut the seat clamp insert out (it's mostly plastic), and removed the dropper, so now have access to the back of the grub screw, although the angle is awkward so it doesn't help

we've used a bunch of cobalt and other hardened drill bits, but not managed to make any progress getting the piece of hex bit out

it's not looking very hopeful

Holy moly OP - I came to this thread for a bit of light relief from Ukraine 😀. Good luck!

an update…

LBS cut the seat clamp insert out (it’s mostly plastic), and removed the dropper, so now have access to the back of the grub screw, although the angle is awkward so it doesn’t help

we’ve used a bunch of cobalt and other hardened drill bits, but not managed to make any progress getting the piece of hex bit out

it’s not looking very hopeful

Could you post some pictures please. Difficult to visualise without seeing what's left.

as spooky mentioned above the tension will be off it now so instead of trying to get the remains of the allen key out can you use a tiny chisel or screwdriver and hammer/something to hit them with and try and back out the screw instead.

I'd love to know the make of those allen keys though so I can avoid them in over 30 years in maintenance I've never broken one, twisted plenty mind you

I’d love to know the make of those allen keys though so I can avoid them in over 30 years in maintenance I’ve never broken one, twisted plenty mind you

I broke a Snap-On Torx bit once, snapped the tip off trying to get the chuck off a drill. Luckily it didn't jam itself in the bolt like the OP. Even the posh stuff breaks sometimes

The only sensible option I can think of now is finding a small pointy Dremel grinding bit and trying to remove it that way.

we're going to try a grinding bit today...

the industrial adhesive approach might also have legs - i have the back end of the sheared hex bit, so if i could glue that either back on to the end of the bit, or in to the grub screw, then we might be able to remove the hex bit or even unscrew the grub screw

does anyone have any experience of what a suitable metal-metal adhesive might be ? it would need properties like:

- viscous - will not flow out of application area
- room-temperature cure
- high stress resistance

Hmm. I'd be surprised if that worked tbh. The glue would have to be stronger than the original hex bit wouldn't it? Is it not possible to get a stud extractor on it?

If your bit has sheared off & the fixing was tight enough to cause this using adhesive isn't likely to work.

In the absence of more information I'm suggesting spark erosion by a local engineering firm. This will remove the offending item if they can get the electrode near the bolt. Large work-pieces can be blighted by broken studs/taps/reamers & drill bits. Spark erosion/disintegration is a proven & reliable technology.

Good luck.

we’ve used a bunch of cobalt and other hardened drill bits, but not managed to make any progress getting the piece of hex bit out

If you can't get a pilot hole in it, the easy-out won't work.

In the absence of more information I’m suggesting spark erosion by a local engineering firm. This will remove the offending item if they can get the electrode near the bolt.

That had occurred to me too, but doesn't the 'workpiece' have to be submerged in some kind of electrolyte? Very dim and distant memory of snapping a drill bit in a hole at technical college here! If I'm right, that might be a sticking point with a bike frame.

Portable EDM is the answer to broken 12.9 fasteners/stud extractors/taps etc. Find a decent engineering company

What is corrosive to the bolt but not to carbon?

Portable EDM is the answer

I didn't know that was a thing, looks very cool

I didn’t know that was a thing, looks very cool

Neat - although tricky with a metal bolt in carbon...

What is the grub now screwed into? If the plastic condom thing in the first image is out, is it not possible to remove the wedge from the frame?

Portable EDM is the answer

EDM. Electronic Dance Music might work| :o)

this is the allie version of the bike, not the carbon - the grub is screwed into the seat tube... there may be something welded inside the seat tube for additional thread depth - i haven't had a look since LBS got the plastic clamp assembly out

spark erosion/EDM looks like it would do the trick though

I think this is the bike - exploded view - link

Looks like it's tapped into the seat tube. EDM or welding an extension on sound the best bets. Welding an extension on often works just because of the heat.

Looks like this with a hex bit snapped off flush?

I have a TIG so would probably weld onto the end to remove.

If I was going to drill the hex bit I would use carbide. Solid carbide drills are easy to snap by hand, but you can sharpen a carbide tipped masonry drill. Would be a pain to drill though. If it wont center punch I have used a dremel to grind a crater to start in.

Welding would be faster/easier for me. (as long as I can get the tungsten in)

currently trying to find someone with a portable EDM machine near me (brighton)

i've found some places with tank-based EDM machines, but the tanks aren't big enough to take a frame, so no good

i've talked with a supplier of portable EDM machines who is going to try some of his customers to see if they can help

What is the grub now screwed into? If the plastic condom thing in the first image is out, is it not possible to remove the wedge from the frame?

grub is screwed into the (ally) seat tube - the plastic clamp assembly and seatpost are removed... it's just the grub screw remaining

Right, assuming that you don't come up trumps with the EDM machine, most good garages will have an induction heater for removing stuck bolts. Oxy-Act used to be the go-to solution for heat. Induction heaters are light years ahead when it comes to removing stuck ferrous fixings. Instead of trying to remove the snapped bit you could get lucky & loosen the grub screw enough to remove everything at once.

If you do track somewhere willing to give this a go, don't go mental with the heat. You could heat that bolt to melting point if the settings are incorrect. Might be another avenue worth trying. If your frame melts in the process remember not to swear \o/

How are you planning on turning it @Davesport once you've warmed it up?

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Steel grub screw into aluminium alloy does put a different perspective on it. It's probably stuck with corrosion. If the EDM solution doesn't come off, heating and cooling should still have a chance. The alloy will expand and contract significantly with heating and cooling, enough to crush some of the corrosion product and allow penetration of fluid into the interface. I've used a 'freeze and release' spray which combines the freezing agent with penetrating oil to take advantage of that. You might also find a weak acid will attack the corrosion with minimal effect on the alloy.

If the induction heater gets a few cycles of heat into the grub screw there are a few options depending on how hard the remnants of the sheared bit are. Its possible that the heating/cooling cycles free the screw enough for it to be moved using a small chisel or punch.

The other alternative would be to knock up a small sharp chisel out an old machine hacksaw blade and see if it's possible to cut a slot in the screw big enough to get a flat screw driver in.

The other thing that occurred to me is that heating the sheared bit could reduce its hardness to the point where a cobalt drill might be able to cut through it. Bit of a gamble drilling things like this as if the drill wanders it could nadger the threads in the frame. Not the end of the world but best avoided.

I did this on a torque bit.
Quite a big head, I got a stainless drill bit the same size as the head, drilled to the end of the head and it popped off, pliers then turned the remaining thread out.

How about drilling a hole in the rear of seat tube directly opposite the grub screw. Then you could drill into the grub screw from the rear hole. The grub screw should be drillable as it's relatively soft (ideally you want a centre punch in the screw). When the drill goes through the grub screw, drilling will stop when you hit the harder hex bit. Then pass a punch through the hole and knock the hex bit out.

The screw can then be removed by a decent hex bit or allen key.

The additional hole in the frame will not significantly weaken the tube and it can be plugged with a bit of silicone or a nice sticker.

Right, I see. None of the commenters in the last hour or so have looked back at the photo's clearly.

It's a bolt head in a pocket with a bit snapped off flush. There's nothing to cut, grip or turn even if heated or otherwise ****ed up. 🙄

Right, I see. None of the commenters in the last hour or so have looked back at the photo’s clearly.

I looked and the solution I've outlined is workable.

You've given me an idea Fruotbat

How about drilling a hole in the rear of seat tube directly opposite the grub screw.

Do that, and then tap in another thread for another grub screw or a collar with said thread if the frame isnt thick enough. File the inside of the stuck one smooth with the inside of the seat tube. New clamping thingy on the other side?

Do that, and then tap in another thread for another grub screw or a collar with said thread if the frame isnt thick enough. File the inside of the stuck one smooth with the inside of the seat tube. New clamping thingy on the other side?

Presumably the seat tube is thicker at the front to allow a grub screw to fit. It looks like the rear is too thin for a thread.

Try my solution first and if it fails then your solution using an external collar would maybe work.

Find somebody competent with a tig welder.

Build out with a filler rod or tack a small bolt on it then you can get a purchase on it.
Extractors are crap, that grub screw and Allen key will be toughened and it will split or crack before it comes out. My worry is it will damage the thread it’s in. The only drill hard enough to drill a hex Allen key is a carbide drill. It’s too brittle unless it’s held in a chuck or collet in a milling machine. It’ll more than likely snap if doing by hand.

Oh.....and throw the rest of your crap Allen keys in the bin.

Wera or Bondhus only.

None of the commenters in the last hour or so have looked back at the photo’s clearly.

I looked at the photo but the OP commented that the plastic assembly had been removed. I assumed that had some relevance to the problem. Not being familiar with this type of seat post I assumed the black area around the grub screw was part of the plastic. If it's not then I agree I wasted my time posting.

None of the commenters in the last hour or so have looked back at the photo’s clearly.

TBF some pictures of the actual bike would help, we are guessing a bit from what it should look like, rather than what it does look like

I'd be wary of putting any heat on a heat -treated alu frame, especially on an area which is exposed to significant leverage forces like a seat tube. Not a frame builder tbough, so happy to be corrected here. My experience of heating alu components almost always leads to ending up with dodgy grain structure and premature failure.
From the photo it looks like the front section of t he seat tube is thickened in the front, to accept the clamping thread. Is this the case? Youve removed the plastic insert already, i believe. If so, can you drill out the clamping bolt from the rear , then if it doesnt spin with the drill, retap the next siz e up, say go from M6 to M8? Im assuming tbe square black section with the i nscribing on it is just a painted effect, not any kind of insert into the frame.

We've had all the sensible suggestions so here's my 'out there' one:

The head of the key is only stuck in there because it's at an angle due to being turned trying to release the bolt. You 'could' get an impact gun and any old bit a suitable size, and try and just shock the head back into position so it can just fall out? Daft but miiiiiight just work. Failing that, a jackhammer!

I would get the bike out of the LBS and take it to a proper engineering shop.  Welding something onto the grub screw / bit of allen key is by far the best answer IMO and you can take steps to prevent heat getting into the frame

Looking at the photos of (not the OP's) orange bike that looks to have a bucket load of blue loctite on the grub screw.

If that's as it came from the factory it'll need a lot of heat if it's stuck. Even then turning it will [now] still be the problem.

When a bolt snapped on me and was buried inside I used a dremel with engraver bits to make a slot on the sheared end, then used a flat bit in a socket wrench, mine was more work though as i had to apply a couple drops of superglue desolver then a soldering iron to heat up the threadlock and managed to undo it. A snapped hex bit should come out easier.

 bucket load of blue loctite on the grub screw.

Good point, worth heating it with a soldering iron to break any thread lock

it's fixed!

spark erosion looked like the best solution, but i failed to find anyone local with a portable spark erosion machine, and my frame wouldn't fit into the tank machines i found

but LBS managed to use a diamond tipped grinder to grind through the grub screw from the inside of the seat tube until they could knock out the hex bit

the steel on allie grub screw (great idea canyon!) was thoroughly corrosion fused in place, so once they'd gotten the grub screw out they drilled and tapped a new hole into the old grub screw, and now i have a slightly smaller steel grub screw in steel, so hopefully it will do better in british winter slop

thanks for all the suggestions!

Congratulations OP.

Pics of it now?

Well done LBS!

Great news! Put some thread lock on it too - that will help prevent corrosion…

Well done LBS!

+1

What was the bill in the end?

but LBS managed to use a diamond tipped grinder to grind through the grub screw from the inside of the seat tube until they could knock out the hex bit

Glad you're sorted & its great that the LBS had the skills to carry this out. When things go wrong the rule book sometimes has to be ignored.

bit more drama... turned out that the M5 retap wasn't enough - the seatpost slipped, and then the thread stripped

so back to LBS for a re-tap at M8 and i'm good to go again. also, the old dropper was kinda shagged, and i've got a new one with 20mm more drop and the collar sitting directly on the seatpost clamp

@weeksy https://photos.app.goo.gl/wkFrNwG8tUXMCcSp6

@footflaps £400 including new dropper. LBS was totally awesome though, and zero-rated quite a lot of (reportedly extremely sweary) hours

by this point, LBS has earned my undying loyalty!

The gift that keeps on giving! Might also be worth using some assembly paste too. That should help keep it in place at a lower torque figure..