Rounded / stripped allen bolt - cylinder head

[XT GIRL]

Learnt something new an amazing today and thought it might help someone somewhere:

When removing my cylinder head cover, I encountered a rounded / stripped allen bolt.

Since all the other bolts were INCREDIBLY INDESCRIBABLY difficult to remove and I broke ALL my fingernails in the process, I thought I was stuffed, since the allen key just twirled round in the bolt head.

(and yes, a feeling of deja vu did overcome me... re the xt girls' famous bolt breaking reputation)

I tried to use a slightly bigger (imperial) key by tapping it into the hole, but the key was too big, and the stupid allen key just bends if you use any impact force on it.

I thought of SLICING the head, to make a slot, to get some purchase, but I was really scared of completely wrecking the bolt and then having to drill it out. (that would have seriously messed up my lunch hour!)

IMPACT DRIVER to the rescue!

On the BRILLIANT advice of a bike whisperer, I used an IMPACT DRIVER with a hex bit that was MILES TOO BIG FOR THE HOLE. In fact, the bit was as big as the bolt head itself.

By tapping square on TOP OF THE ROUNDED HEAD with the oversized bit on the impact driver, the impact caused the bolt head to FATTEN OUT (sorry, best term I can think of to describe it) - which caused the stripped hole to SHRINK!

AND - using an impact driver, means you are not damaging anything else. (I think.)


THEN, I could use a bit that FITTED in the shrunk hole, and used the IMPACT DRIVER to turn the bolt out!

IMPACT DRIVERS RULE!!!