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/
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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..
