just recently i removed my stem on a look 595 for inspection. the stem was fine but when i went to tighten the top cap bolt i used a 3/16" instead of a 5mm allen. i want to remove the bolt and replace it because i forgot to put a shim on the headset.

If u stripped a 5mm allen head using a 3/16" wrench, uthat mrans u are applying way too much torque to ur top cap. Even using the 3/16" wrench (albeit not recommended) u could easily reach the MINIMAL torque necessary (1.5-2 Nm) to preload ur bearings. Here is a primer on how to properly adjust a threadless headset:
http://www.parktool.com/blog/repair-hel ... et-service

Try finding a crisp/new 5mm and try to fit into the stripped head or as a crude alternative a sharp edged flat head screwdriver that fits snugly withing the head might also do the trick.
EM3

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My 2011 Cervelo R5

The problem is that the bolt is recessed about 2 cm in.

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Tiny explosives

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Drill a small pilot hole. At the store ask for the section with the it extractors and ask what bit you need to drill with first.You shouldn't have to drill to deep. After that, use the bit extractor by hand, . Remember that it is reverse threaded so it will pull the bit out as it goes down.

the picture

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I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

...are you talking about your headset top cap or the compression plug/insert in your fork steertube?
EM3

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My 2011 Cervelo R5

Be careful using those screw extractors. I call them ez-breaks instad of ez-outs, because you're more likely to snap it off inside the stuck screw than you are to remove the screw. Once you break it you are really screwed, as the extractor is harder than your drill bits.


You should not be putting significant torque on a headset cap screw. Loosen the stem clamps before turning the cap screw.

If the extractor is harder than your drill bits why would it snap off?

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I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

Easier, get a drill bit thats wider or same width as the thread but narrower than the head and just drill down the head until it breaks off.

Remove top cap

Clamp Mole grips on remains of bolt and unscrew

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Nanobots ?

Hard steel is brittle.

Eric, extractors are made to extract bolts. This is a puny top cap bolt which is low torque. We are not talking about a rusted bolt that is seized. Please.

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I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

...

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Before all this try a less aggressive method,

Remove handlebar, loosen stem bolts and keep turning the stem - the top cap and it's bolt will most likely come loose for you to finish off by hand.