Well, I sheared the head of a bolt while trying to replace cranks on my cotterless hub…what’s the best way to get the rest of the bolt out?
Go to an auto parts store. There are things called “easy outs”. You drill a small hole in center of bolt (drill bit usually comes with) and then use the "easy out " to remove the bolt. Not to expensive and fairly easy to do. Make sure you tell them the size of the bolt.
The one time I faced this on a motorcycle the bolt came out with the left hand drill bit. Didn’t end up needing the easy-out.
Did you over-tighten it or is it seized up? If seized up its most likely gonna need the easy-out.
Just curious if you have any idea what torque the bolt took before shearing.
I had the torque wrench set at 50… I know, I should have had it at 40. Also, my torque wrench is old and I am not sure it’s accurate. I’m going to buy a new one today.
If it broke because of high torque then the axial load is probably gone. You may be able to rotate it with a punch. Sharpen a hard punch without getting it hot. An old drill bit can be sharpened to become a punch. Punch close to the outer edge of the broken piece then drive it in a circle. Cheapest solution if it will work.
I would second the recommendation to first try drilling it out, if you feel confident about doing that. You can also take it to an automotive machine-shop and have them remove it; it shouldn’t cost that much.
A punch on a small bolt is never going to work you can’t get far enough away from the center. I know I’ve tried that technique more than once and its never worked for me. It has only worked for me when I was an industrial tear-down mechanic working with large bolts.
The only problem I forsee is that I’m pretty sure the bolt is hardened. I tried to dril a small hole to use an extractor and barely made a dent in it. The drill was not very heavy duty so I may try again after a friend tries to get it out.
I guess I’ve been lucky 20 or 30 times but we usually use grade 8 screws in medium hard threads in our molds and other small tooling. Yes, odds are against you but never say never. Soft steel and stainless is really prone to galling and you might as well go straight to the extreme measures.
On the plus side…I’m having an ISIS wheel built up for meso I’ll only use the other wheel (with the broken bolt) as a spare and can take my time getting the broken bolt out. 
I’m a do-it-yourselfer and I do repairs on my cars a few times a year. Several months ago I was struggling to loosen a bolt. For the first time I used a propane torch to heat it up and I could not believe how easily it came out.
Of course it seems like most of time there’s a bunch of plastic or rubber or flammables near the part I need to heat, so I don’t. I need to get a more focused torch.
Not sure if heat could help the situation in this thread. Maybe heat and the punch technique? I imagine bearing seals would melt though. Maybe if the spindle was completely removed from the hub first? But I’m picturing a bike hub. I’m almost embarrassed to say I don’t even know all the parts of a uni hub. I haven’t been into it long enough to take one apart.
Buy a left hand drill bit (yes, they really exist).
Use a center punch to mark the center of the bolt and make the drill
stay on center.
Use a high torque drill (like a 110V one, not a weak cordless)
Push hard - when the drill bit bites in, it will grab and will spin the bolt out.
If it doesn’t grab hard enough to unscrew the bolt, at least you’ll have
a hole for the easy-out.
Here’s a start…
Use the links above to help find them.
I’ve heard that extractors and easy-outs can break. When that happens, then you’re really hosed, because the extractor itself is hardened, and it’s now in the way of the original piece.
That happened to me, although not on a uni. It is a real horror, the easy out thing is super hard.
Use the center punch, and as large a drill and as big an easy out as will fit. A vice and a drill press are great if you have them.
I’ll second the use of a left hand drill. They will remove material down the center and along with that material a lot of the radial pressure goes away. Then, as previously posted, it will grab and screw the piece out.
But,
Even though a center punch mark is required to keep the bit from drifting while starting, it can work harden the steel. This work hardened spot can ruin the tip of a cheap drill. The only left hand bits that I’ve seen were low grade. Maybe use a small regular drill bit after the punch and before the left hand bit to get the work hardened material out of the way. That will at least preserve the rarer left hand bit.
Actually, that’s a good idea.
Drill a smaller hole with a right hand bit (a pilot hole) part ways
and then chase it through with the larger left hand bit.
Drill bit usually cut aggressively when they are following a
pilot hole, so it will put a lot of torque onto the screw and
likely will break it loose and spin it right out of the hole.
Well thats odd because as an automotive technician for over 20 years, I use this method at least 3 times a year with an 85% success rate as long as it’s not corroded…
Small bolt? Use a smaller center punch, or my favorite is the corner edge of a chisle… Just tap it in till it grabs and start working it around… Problem with drillingit is if you break the hardened drill bit off in the bolt you’ve just tripled your work load unless you have colbalt bits or something just as nasty.
Take it to your local garage with a dozen doghnuts and maybe a cup of coffee or two, One of the techs will probably offer to do it on his lunch break.
I can’t think of a best way, several lucky ways though! always start with a reverse drill bit -you might get lucky! then try an easy-out, then try the square things like this you find at sears… is the thing rusted in? PB blast sitting overnight helps, so will heat… Stubbornness is usually what works!
