Best way to remove stripped bolt
 

I bled my brakes and went to align the caliper but the hex slot on one of the bolts is rounded out, so I need to drill it out. I've successfully removed stripped bolts before but never on one stuck in a carbon fiber frame, so I'm a little concerned about doing damage to the threads. Any special info or technique I should know?

Thanks all in advance

Joe


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The best way is any method that works.

Can you not grab the head of that bolt with some small needle nose vice grips and get it turning?

You could also just drill the head off the bolt and try grabbing the shank with vice grips once the brake body is out of the way.

You'll need another bolt to replace it with.

Any damage to the carbon fiber you'll just have to deal with after the fact. Just like you would with a steel or aluminum bike. Though the techniques you use won't be the same if you mess the CF up.

Don't see any reason you should damage the carbon fiber. The head of that bolt conveniently has ridges that will make grabbing it with pliers or needle nose vice-grips easy enough and then you are just unscrewing as if it wasn't stripped. I have also had good luck wedging a Torx bit into stripped hex bolt and getting it to unscrew that way. You will need to replace the screw, when you get it out. good luck

You can use inverted thread tools set as in the picture below. You carefully drill a small hole in the damaged screw. Then you screw the inverted thread tool in that hole by rotating counter clock until it blocks, then continue rotating counter clock to unscrew the damaged screw.


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Dremel, or chisel. And a screwdriver.

https://www.bestlife52.com/img/tool/...s-on-bolts.jpg

That situation calls for a very small slip-joint pliers, sometimes called "ignition pliers".
Often a needle-nose will slip off - the mechanical advantage is so low that you can't keep the jaws gripping.when you try to turn it.
Needle-nose vicgegrips will work, if they fit (and you have them).

There are special pliers designed to help with that, but sometims you just have to drill the thing out.
https://m.media-amazon.com/images/I/...AC_SL1500_.jpg

https://cimg4.ibsrv.net/gimg/bikefor...584fdae37.jpeg
This is what he's talking about.

Left handed drill bits, frequently coupled with screw/bolt removal tools such as pictured by Red Bullet above can be helpful
as well as they turn/cut in the direction that removes the bolt. So a reversible drill is needed, not hard to find. The pliers
from Neji-Saurus are 8' long so the jaws may be too large. A 5-6" long slip joint might work such as sweeks pictured but
the only one I can find at 5" is Knipex ($35), most are 7-8" at the small end but grinding the top part to thin it down might
work.

Hex extractor bits

8 Piece Metric Zeon Hex Bit Socket Set

https://shop.advanceautoparts.com/wc...5_pri_thmb.jpg

4"
​​​​​​https://www.mcmaster.com/5392N12/

I think the proximity of the caliper body to the bolt head will interfere with using pliers. If it were me I would try extractors first. If that doesn’t work I’d next try slotting the head with a Dremel.

This would work well. Vise Grips come in many sizes. I rarely use on my bikes - mostly other projects.
Make sure your replacement bolt is in your hands before extracting. My preference involves replacing with a hex-head bolt, if you can find one.
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have you tried putting a dab of Valve Lapping Compound in the socket, and/or fitting a torx or american allen wrench in there?

the lapping compound acts as TRACTION for the wrench in the socket. It WORKS, in many cases!
tip from Hot Rod Magazine, in the late 1960s... i've used it countless times over the decades.

the threads are a threaded insert, commonly called a "Rivnut"(there is more than one design of rivnuts)... the worst case is that the rivnut breaks free in the CF frame, and begins rotating with the screw/bolt.

i'd try the lapping compound/torx bit first, followed by the reverse drill and extractor.
i'd also consider looking at the end of the allen wrench you're using... they get worn out, especially my 5mm allen, and the 4mm too... i freshen up the working end on the side of my grinding wheel, making sure to quench it in water frequently.

None of the listed (1/4" drive) tools will fit--the caliper screw in that position will prevent anything wider than 5.5 millimeters from turning without damaging the caliper paint/body.

You should start by center-punching the socket, and use a small bit to bore a hole 10mm deep. If the head breaks/is otherwise damaged, it will become invaluable. When/if visegrips or pliers fail, drill the head off, remove the other screw, and remove the caliper (taped out of the way). Enlarge the hole to ~1/8", and use a #2 extractor to back the stub out. You may find some help in applying a hot soldering iron to the screw for a few seconds, to help break the extremely heavy threadlock that Shimano puts on the screws.

Thanks for all the help - it is much appreciated.


The bolt is set too deep in the body of the caliper for needle nose vise grips, already tried that. Even if you get a bite, the caliper body knocks the pliers off the bolt once you start turning. Im gonna go with the extractor probably, that's what's always worked in the past... and I like the lapping compound idea, may try that first.


Lyk how it goes...

make sure there's a nice crisp edge on the allen wrench too... the 5mm always wears out first.

Is there room to remove the head of the bolt with a dremel cutoff disc? Then you can grab the bolt remains with vise grips after the caliper has been removed.

Just drill the head off with a bit that is as close to the dia of the bolt (not the head) as possible without being any larger. You'll be left with a stub that can be grabbed with some vise grips. This will also leave you with a pilot hole left from the drilling to use a smaller drill bit for a bolt extractor if needed.

If you're going to drill it use a left-handed drill bit - sometimes a bolt will just unscrew when the drill grabs.

Don't do any of the things other people told you to do here. Here is what you do - Take the other screw off. Now rotate the entire caliper counter-clockwise around the stuck bolt. All you need to do is swing it outwards roughly 30 degrees. That will expose the 2 caliper mounting screws under the adapter piece. Loosen those two screws and remove the caliper from the adapter. Now you can go to town with the adapter and the stuck screw.

Brilliant - gonna try this first. Hope it works!

This working beautifully, caliper came right off so I could get the pliers in there onto the stuck bolt, no drilling. Thank you!