How to get rounded bolt out of a Thompson stem?
Like an idiot I’ve rounded one of the steerer bolts in a Thompson stem.
I’ve tried torx bit- to big or to small, no purchase.
I’ve tried a different size allan key, no purchase.
Next option (s)
Cut a slot. this will involve cutting a signigificant amount of stem- difficult and unlikley to work as the bolt head is so small.
Drill it out. Last time I tried to drill an steel bolt out of alloy, i made a right hash of it.
Cut the bolt through the gap? Might lead to damage to the fork steerer.
Take it to the bike shop.
Any better suggestions? Its soaking in wd40 nowPosted 9 months ago
LBSPosted 9 months ago
Easiest way to get it out without further damage to the stem is to drill it. All the other options damage it anyway so may as well try it. Make sure you have a sharp bit just a bit smaller than the bolt diameter.Posted 9 months ago
My approach would be to drill the head off with drill bit slightly smaller diameter than the head, drill stump of bolt from behind (with a drill bit smaller than thread core diameter obviously), if it isn’t seized it should catch and spin outPosted 9 months ago
Forgot to say, once head is drilled off you will be able to get the stem off and put in a vice which will raise your chances of drilling the the stump out squarely significantlyPosted 9 months ago
Tighten up the other bolt to reduce the tension on the knackered bolt an use something like This on the stripped head.
Or take it to a bike shopPosted 9 months ago
If you’re drilling it out, use a left hand drill bit – might get the bolt out in the process.Posted 9 months ago
As Phil H says, tighten up the other one, then try the torx bit method again.Posted 9 months ago
If you fail, drill.
Can you get a clamp on the outside of the stem where the rounded bolt is? Tightening it (while you still have access to the bolt) would take the load off in the same way as tightening the lower bolt, but more directlyPosted 9 months ago
Agree with Phil h.. Be careful doing the other bolt up further but never had it fail on me yetPosted 9 months ago
Per Phil H – just ordered one of those hex bolt extractors – there was a similar one for just a tenner – looks pretty useful…Posted 9 months ago
Thanks for the suggestions!
I’ll clamp up the other bolt, try and get it in the vice and drill it with a fresh bit. Then drill from the other side.
I can’t get anything to catch as it is now.
I’ve got a set of bolt extractors from my last adventures in drilling a stripped bolt out of a crank.
I’ve mentally written the stem off. So if it’s ok, That’s a bonus.
Photos tomorrow 😀Posted 9 months ago
Impact driver?Posted 9 months ago
I’ve seen an impact driver remove a fair number of frankly unlikely looking bolts. Bit pricey for one bolt, but a great tool to have.
id cut the bolt through the gap in the stem, top half should fall out. then a left hand drill bit from the back should get the bottom bit of bolt out as it wont be tightPosted 9 months ago
When i say impact driver i mean something like this one, not a battery or air powered tool btw.Posted 9 months ago
Tighten up the other bolt to reduce the tension on the knackered bolt….
Would never have thought of doing that.👍Posted 9 months ago
Can you use the greater thermal expansion of aluminium to help, eg by putting the stem in some boiling water or using a hair dryer on it.
Also, get some proper penetrating oil rather than wd40.Posted 9 months ago
I had the same recently, also in a Thomson stem.
Didn’t think about tightening the other bolt and easy outs didn’t work.
Ended up cutting it with a dremal through the gap. Very easy to do and causes no damage to the stem of your careful, but beware of the tension it is under.
The bolt head went with such a force that it made quite a clatter as it hit the garage door – wouldn’t want to be in its path.
Still leaves half a bolt on the thread which I haven’t yet got out as the stem is only used on an indoor trainer so 1 bolt will suffice.Posted 9 months ago
Cut the face plate off, mole grips on the bolt. Then buy a new face plate.Posted 9 months ago
Also invest in a torque wrench – they’re not too expensive from eBay or similar….and thread lock can be your friend here. It’s not just to stop bolts coming loose, it will also stop them seizing in place. That’s why I always use it on cleats.Posted 9 months ago
Cut the face plate off, mole grips on the bolt. Then buy a new face plate.
That’s great but doesn’t help much with the rounded steerer bolt and seems a waste of a faceplate 🙂Posted 9 months ago
<Cut the face plate off, mole grips on the bolt. Then buy a new face plate>
My understanding is its the steerer bolts not the handlebar bolts that he needs out>Posted 9 months ago
This is STW. Proving solutions the OP didn’t ask for. Should think themselves lucky I didn’t go straight to victim blaming.Posted 9 months ago
Another thought – drill it with a bit which is slightly smaller than the thread size, then try the torx bit again. This can work if you have a torx bit with a taper on it. The drilled hole allows you to hammer it home further and get a better interference fit.Posted 9 months ago
Flat head screwdriver. Bang it in til it grips or if bolt protrudes enough cut a slot across top of bolt for it to grip.Posted 9 months ago
Nah, no victim blaming, Thomson bolts aren’t much cop tbh.Posted 9 months ago
As mentioned above, use an EZ out or damaged bolt remover. I got mine from Screwfix years ago. One of the best tools I have ever bought. Will be out in less than a minute.Posted 9 months ago
And buy some decent hex keys.Posted 9 months ago
I used a dremmel to cut the top bolt.
It went with a bit of a ping!
Ran out of garage time to drill the other half of the bolt out.
I’ve gouged the gap between the two sides of the stem slightly. Perhaps doubling the size of the gap.
Would you ride a stem like that? This is assuming I can get the other half out.
MartinPosted 9 months ago
The problem was caused by a slightly under sized hex key on the multi top that lives on my bike. Used that,felt the bolt go a bit.
When I got home and tried a park tool one it rounded completely. The same park tool one has now twisted getting the other bolt out. 🙄Posted 9 months ago
Worth loosening and retorquing your other bolts I’d suggest to prevent a recurrence.
Oh and I’d probably use the stem but get a new one for Christmas or birthday!
My mate has a habit of putting a ‘farmer’s nip’ on all his bolts, thus ensuring they are impossible to remove again!Posted 9 months ago
Second the suggestion to invest in good Allen keys(wera) ones are very goodPosted 9 months ago
Thomson bolts aren’t much cop tbh.
Thomson bolts are fine. They are speced to round when a punter ramps up the torque beyond the design torque……Posted 9 months ago
I still find them very delicate (using a torque wrench with decent allen key head).
And all very well designing them to round if over torqued but how do Thomson then expect the ham fisted person to get the rounded bolt out. Other stems don’t resort to silly little sizes do they?
I like Thomson stems and have one on my bike but the bolts are a pain.Posted 9 months ago
+1 dodgy small bolts. I think the idea that Thomson fitted bolts that intentionally round above a certain torque is laughable. They just specced silly small bolts, that’s all.Posted 9 months ago
A few reasons:
1. We think they look nicer.
2. Serrations have been removed to lessen corrosion.
3. Most importantly, the Allen socket has been dropped from 4 to 3mm. This will act as a torque limiter as in most cases you cannot get the bolts tighter than 55 inch pounds. The 4mm socket bolts could get as high as 150 inch pounds. This should help riders without torque This should help riders without torque wrenches avoid damage to stem, bar and steerer.
55in-lbs is 6.2nm – the spec for the x4 is 4nm and the x2 is 5.1
people were overtightening them and splitting the faceplace across the middle – as folks still do with hope stems.Posted 9 months ago
I found the bolts to be as soft as cheese and rounded too easily. That’s using a torque wrench. And every time I hit a pothole, my Ritchey bars would rotate. I eventually binned a 120mm stem for this reason. Still have a 110 mm stem on another bike, but I haven’t needed to adjust that.
They also scratch more easily than any other stem I own (and I own over 25).
Ritchey also spec small bolts on some of their high end carbon stems. I have yet to round one of those bolts.Posted 9 months ago
Good allen keys and i also pop a bit of copper slip on the bolt ends for aiding when i come to remove/adjust stem months/years later.Posted 9 months ago
Bolts are soft as cheese and rounded too easily, even used with a torque wrench. for the remaining bit of bolt you try pushing it out from the other side with a small screwdriver – it should turn easily now (that’s how we got the rest of the bolt out of katie’s stem)
Issue we were having before is that the lower torque they’re speccing wasn’t enough to keep the stem straight – even a very minor low speed off would turn the stem on the steerer. All very well using a torque wrench in the workshop but it’s not going to happen at the trailsidePosted 9 months ago
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