How to get rounded bolt out of a Thompson stem? – Page 2 – Bike Forum

tall_martin · 2019-11-30T17:34:59Z

Hi, 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 now

tall_martin

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Topic starter

Posted : 02/12/2019 10:48 pm

madmechanist

Posts: 0

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As mentioned cut through the gap..then drill from the stud side(NOT HEAD SIDE..this is under tension on the bike wont go through right..) then undersized drill the file out remnants if neccisary only if it doesn't unwind with a extractor..clean threads copper slip/grease new (4mm!!) Allen bolt or better a t20/25 then that almost certainly wont round out even when stuck..also try bashing it with a soft hammer(breaks the bolt thread tension a bit)..

Posted : 03/12/2019 2:11 pm

squirrelking

Posts: 11605

Free Member

As mentioned cut through the gap..then drill from the stud side(NOT HEAD SIDE..this is under tension on the bike wont go through right..) then undersized drill the file out remnants if neccisary only if it doesn’t unwind with a extractor..

Username checks out.

I know what to do and I'm having a hard time following that.

Posted : 03/12/2019 4:24 pm

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[Closed] How to get rounded bolt out of a Thompson stem?