[Closed] Rounded off bolt - Thomson stem woes

I have an old torx socket set which I use to get rounded allen bolts out.
Just use one slightly bigger and tap it in, it will usually bite enough to crack the bolt.

Do you have a drill/driver with an adjustable clutch ?

You can use the clutch and set it to slightly less than it needs to be and use it a bit like an impact wrench. This will loosen the other bolts and should help with the damaged one ?

Only one bolt stripped? Get a high quality allen key in the other bolt and tighten it. This will reduced the force acting on the bolt with the damaged head and you will probably be able to undo it then. Then put another well greased bolt in and do the same to get the second original bolt out.

Or indeed use an impact driver.

Tim, yes only one bolt (left side) is rounding off, the other side took a bit of swinging on to get it moving. Had to get the socket set out and standard Allen key wouldn't do anything.

It was done up tighter than my cars wheel nuts 😯

Not got a impact wrench but the drill's got a slip clutch. So I'll try that with the other side tightened up.

Tish: when you say crack the bolt do you mean to get it moving or actually crack the head.

Thanks for the tips.

By crack it I mean loosen it, if it rounds again you can sometimes use the next size up.
It's a bit rough but it has got me out of a tight spot a few times.

Thought so, but thoght I'd better check.

Thanks Tish

I tried the methods above but they didn't work.

So I've got the drill the bolt out, I got some TiN bits, they started off well but aren't doing anything now, so can you recommend a decent set of metal drill bits?

take it to a shop 😐

Eyerideit

Doesnt matter what drill bits you buy if you swing off em like an orangutang they will blunt just like your current ones.

Get some cutting fluid or light oil and keep spraying it over the bolt as you drill to draw the heat out

When you did what Tim suggested, did you first remove the decent bolt and give it a good coating of grease? That bolt interface is pretty bad and I've seen various ones snap over the years. If the bolts are at least greased well, they will tighten up a bit further without seizing / snapping / rounding off and it might be enough to relieve the pressure on the other bolt. However you get the offending bolt out, take care to tighten the replacements up just enough so the stem doesn't move around on the steerer.

Ah, reading again you are already drilling away at the hardened steel bolt....have fun!

They are high tensile bolts, so you'll need a decent drill bit and take it steady or you'll drill the stem. I'd go with Tims suggestion above but maybe try and get some penetration fluid around it if you can.

Having done this myself and destroyed the stem, I'd be drilling as a last resort.

Drilling out bolts is something that most people will fail at. Not a criticism of you, but it's not easy, and here you've got a very hard bolt in a very soft alu stem too. It's a one-shot deal so I'd recommend a shop.

(it's something I've done quite a few times, due to owning a Suzuki, and even then, I approach it with a lot of caution it's much more easily done wrong than right)

can you use a puller to get the stem off the steerer? Would lossen the tension off the clamps so you could get them out of the stem and get into a proper bench drill.

Yes I did exactly what Tim suggested but the bolts are in so tight that the splines on the Torx bit started to distort.

The bikes second hand so whoever put the stem on used a superhuman amount of force and no copper slip/grease

I'll buy some decent Bosch bits and drill it out squirting in WD40 along the way. I'm about half way through the head so I'll keep on drilling.

These bits are quite a bit tougher than your common or garden Bosch ones from B&Q. My Bosch TiNi coated ones blunt as soon as they see something tougher than aluminium.

http://www.toolstation.com/shop/Power%20Tool%20Accessories/Cobalt%20Drill%20Bits/Cobalt%20Drill%20Bit%20Set/d80/sd1230/p40442

PS, use coolant, and ideally use a pillar drill with the stem clamped in a vice. It's blimmin hard to hold a handheld straight enough all the way through.

+1 for cp with the cobalt drill bits - just been drilling 316 stainless at work with some to good effect (HSS won't last).
Use a sharp drill, light pressure, and get someone to pour a steady trickle of cold water over it whilst drilling to keep it cool. HTH.

Ordered the bits and some cutting fluid. Thanks for the link and tips CP and Chives.

I just need to get the head off then the rest is easy, my TiN bits have done about half of it, so hopefully these will get the rest done.

I have an old torx socket set which I use to get rounded allen bolts out.
Just use one slightly bigger and tap it in, it will usually bite enough to crack the bolt

+1 for this works for me

I'm no meturllagist but would a period in the freezer or oven help at all considering the differing metals involved? I've no idea myself but interested if anyone could elaborate.

just drill a small hole through then torx the head it will shear off

Another Method

Get old 'Sacrificial' allen key and lightly weld it to the bolt (sounds like Glue would not be strong enough)
This will give you enough leverage to remove the bolt

it does mean you have to buy a new allen key and a new bolt but certainly better than drilling etc

Thanks to CP's rec for the cobalt drill bits and cutting fluid, finishing the job only took 15mins of drilling this morning using the garden bench and my cordless drill.

The amount of material coming away was impressive. I was using cutting fluid, applying minimum pressure and taking my time. Suddenly the whole thing made a bang and retaining plate shot out of the bottom, because the bolt was so that tight.

Thanks to all the advice above, you've saved me a lot of time and having to buy a new stem.

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Thanks again STW.

*pats on backs all around*

Not bad! Consider yourself in the elite group that can actually drill out a bolt without horribly destroying everything.

I had the same problem, got my neighbour with a mini machine shop in his shed to sort me out.