Bicycle Mechanics - M5 bolt broken in threaded eyelet: best way to remove?

i recently got a frameset back from the powdercoater's which i've been building up. i tried threading an M5 bolt into the fork-monted fender stay threaded eyelet, but the threads hadn't been properly chased. the bolt threaded in about half-way before it started to feel tight. i didn't think i was applying too much torque, but it eventually snapped! it was a stainless steel bolt. i'm guessing i have no option but to drill it out.

what is the best approach/what is the best type of drill bit to get this sucker out?? i need to preserve the integrity of the eyelet threads, and i don't want to damage the powdercoating around the eyelet. this is a reynolds 531 fork (from a raleigh competition, link in signature to pics) and i *really* don't want to damage it. i know i will have to be careful. i've been toying with several options: first, drill a small hole in the center of the bolt and thread a self-tapping screw into it from behind (since the eyelet is open in the back!). hopefully the clockwise threading of the self-tapping screw into the broken bolt will drive the bolt to thread back out the same way it threaded in. second option: use a larger drill bit closer to the diameter of the bolt, causing it to more or less disintegrate inside the eyelet. there is more risk of damaging the eyelet threads this way, but the first option may not work.

what are everyone's thoughts? any other ideas? any special tools that i should consider?

You might have luck with a screw remover. Any decent hardware store should have them. They're basically a left-handed self-tapping screw type thing that as you thread it into a hole you drilled in the broken screw it unscrews the broken one since they're opposite-handed threading. This would be better for the threads in your frame's eyelet than trying to drill out the broken screw completely.

Center drilling a 5 mm bolt to allow use of an EZ-out is tricky at best. Is there any stub still sticking out of either end? If so you could slot it with a Dremmel and a cut off wheel and try to remove it with a screwdriver.

Center drilling a 5 mm bolt to allow use of an EZ-out is tricky at best. Is there any stub still sticking out of either end? If so you could slot it with a Dremmel and a cut off wheel and try to remove it with a screwdriver.

If there IS a stub, try using a pair of locking vice grips on it before slotting it . Then do what hillrider says. If that fails, your only option is drilling it out. If the drill fails you may still be lucky enough to get a tap through it and have the threads hold. I've never had much luck using easy-outs on high torque m5 snap-offs like that.

When drilling out a bolt/screw, you always start will a small pilot hole as centered as possible (perfect centering is not as critical as you might think). From there, step your way up until the drill breaks through the minor diameter of the bolt/screw at which point it will be relatively easy to remove. If your pilot hole was off center, this will only happen for a partial section of the circumference but breaking that hoop will still greatly weaken the screw's grip. With a cross-threaded/seized screw like yours, I would avoid trying to force it the rest of the way through as re-threading will be very difficult. I would also avoid an EZ-out (screw extractor) at all costs. You are way more likely to break off the hardened steel extractor in the screw stub than be successful. Trust me on this. BTDT. It's not fun. Screw extractors have their place but a small, seized-in-place fastener is not it.

I highly recommend the step drilling method then retap from the inside of the fork. This will help guide the tap through starting with the hopefully good threads. Starting a tap straight in a cross-threaded or otherwise damaged threaded hole isn't easy without a fixture.

Drilling a stainless screw will be difficult. The SS work hardens. Get a carbide bit to drill a small hole then use an easy-out.

If there IS a stub, try using a pair of locking vice grips on it before slotting it . Then do what hillrider says. If that fails, your only option is drilling it out. If the drill fails you may still be lucky enough to get a tap through it and have the threads hold. I've never had much luck using easy-outs on high torque m5 snap-offs like that.



Center drilling a 5 mm bolt to allow use of an EZ-out is tricky at best. Is there any stub still sticking out of either end? If so you could slot it with a Dremmel and a cut off wheel and try to remove it with a screwdriver.


it did have a stub, but i didn't think of dremmeling out a slot for a screwdriver. i used the vise-grip method, and it wore away the stub without any luck. however, i think if i had made a slot with the dremel, the slot would have broken under the torque of a screwdriver.


I highly recommend the step drilling method then retap from the inside of the fork. This will help guide the tap through starting with the hopefully good threads. Starting a tap straight in a cross-threaded or otherwise damaged threaded hole isn't easy without a fixture.

good idea. the bold did not reach the back half of the threads. i should be able to get a good tap going from that side of the eyelet once the old bolt is removed (and if i've damaged any threads in the process).

. I would also avoid an EZ-out (screw extractor) at all costs. You are way more likely to break off the hardened steel extractor in the screw stub than be successful. Trust me on this. BTDT. It's not fun. Screw extractors have their place but a small, seized-in-place fastener is not it.
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Oh please.

Just because you have ****ty ez-outs doesn't mean everyone does. http://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443290988&FOLDER%3C%3Efolder_id=1408474396672926&bmUID=1261073082532

Can you see the back of the hole and access it? If you can, it will be easier to drill out from the back, and the drill will probably catch and turn it out anyway.

or drill it through from the front side then put a small self threading screw in from the back side. This will unscrew it.

Can you see the back of the hole and access it? If you can, it will be easier to drill out from the back, and the drill will probably catch and turn it out anyway.


or drill it through from the front side then put a small self threading screw in from the back side. This will unscrew it.

i mentioned in my first post the answers to both these questions: exrunner, yes, the eyelet is accessible from both sides. cyclist, this was my idea #1. it seems like my ideas are meshing with everyone elses, so that's good!

For future reference: always chase threaded fittings after paint/powdercoat before trying any fasteners! It takes but a moment, but can save hours of grief.

Oh please.

Just because you have ****ty ez-outs doesn't mean everyone does. http://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443290988&FOLDER%3C%3Efolder_id=1408474396672926&bmUID=1261073082532

Did you read that comment in context? I've used EZ-outs successfully several times and been very happy with them. In his situation, an EZ-out would be my last choice. There are easier and safer methods for what he's trying to accomplish.

For future reference: always chase threaded fittings after paint/powdercoat before trying any fasteners! It takes but a moment, but can save hours of grief.
yep, you're right. i should have, but didn't.

okay, now i'm f***ed. joejack was right on the money. i went ahead and bought a bolt extracter. i drilled a perfectly centered hole in the broken stainless steel bolt, got the extracter in, applied some torque (much less than was required to break off the original bolt), and it snapped!!! and now it's worse, when i try to drill the extracter out, it's just too hard. my bits can't handle it. i am going to have to bring the fork to a frameshop and have them drill it out. damn. and i was so close. if i had chosen the alternative method (joejack's method: drill a sequentially larger hole) i could have gotten this bugger out, easily. now i have to pay someone else to do it. :mad:

Sorry for the trouble.

I never actually broken an EZout, but then I've never been able to remove a bolt with one either. I did manage to drill out a bolt once, but I damaged the threads a bit doing this. Either way, it's a pain.

okay, now i'm f***ed. joejack was right on the money. i went ahead and bought a bolt extracter. i drilled a perfectly centered hole in the broken stainless steel bolt, got the extracter in, applied some torque (much less than was required to break off the original bolt), and it snapped!!! and now it's worse, when i try to drill the extracter out, it's just too hard. my bits can't handle it. i am going to have to bring the fork to a frameshop and have them drill it out. damn. and i was so close. if i had chosen the alternative method (joejack's method: drill a sequentially larger hole) i could have gotten this bugger out, easily. now i have to pay someone else to do it. :mad:

A small grinding bit used with a Dremel tool will eventually remove the remains of the screw extractor. To machine it out. only a solid carbide end mill will cut that hardened extractor. At least your fork is easily set up on a milling machine if it comes to that. Actually, you might try drilling through the opposite side of the screw then knocking the broken extractor out with a punch.

Whatever you do, don't try another extractor in the screw after you get the first one out, not that someone here has ever done something THAT stupid :o

A small grinding bit used with a Dremel tool will eventually remove the remains of the screw extractor. To machine it out. only a solid carbide end mill will cut that hardened extractor. At least your fork is easily set up on a milling machine if it comes to that. Actually, you might try drilling through the opposite side of the screw then knocking the broken extractor out with a punch.


hmm... it didn't even occur to me to try to just punch it back out since the thread pitch is so steep, essentially like a drill bit's. the tapered tip of the tool is actually sticking out of the back end of the eyelet by about 4mm. it threaded all the way through the broken bolt before grabbing. i may try tapping that back out first. if that doesn't work, i'll try a dremel grinding bit.

if i can just get this damn extractor out, i'll be golden. it was easy drilling through the SS bolt dead center, and it should be equally easy to drill larger bores until the bolt collapses.

I broke an extractor off in an engine block. It was hard enough that I could just break up the broken end with a hammer and punch. Your situation is a little more delicate so breaking it up may not work but it wouldn't hurt to try to knock the extractor out from the backside with a punch.

You still have the back side.

hardened steel tools like extractors and taps can be removed very easily with a punch and hammer. The qualities that allowed them to break so easily also allows a punch to shatter them very easily, you just have to be careful. I have done it many times.

Once you get the stuck bolt/extractor/etc. out, if the existing threads are damaged beyond repair you can:

1. Drill the hole to to 5mm clearance diameter for and use a nut and bolt to fasten the fender stay.

2. If there is enough metal around the current hole you could drill and tap it to M6x1.0.

Once you get the stuck bolt/extractor/etc. out, if the existing threads are damaged beyond repair you can:

1. Drill the hole to to 5mm clearance diameter for and use a nut and bolt to fasten the fender stay.

2. If there is enough metal around the current hole you could drill and tap it to M6x1.0.

good ideas. there is plenty of clearance at the back of the eyelet for a 5mm nut, and cosmetic-wise it wouldn't look bad to have a nut on both L/R eyelets for symmetry. i'd rather do this than retap to M6. but let's hope i don't destroy the M5 threads!

i will look for some dremel grinding bits tonight!

If you can't get the extractor out,find somebody around you that does EDM work and let them take the whole mess out.They will preserve the 5mm threads also.Should run you about $50.00.

update: i had success!!

plan A: failure. i bought a dremel grinding bit that was supposedly suitable for hard metals, and tried it. no go. it wouldn't grind through the hardened extractor. all it would do is polish the exposed stub of it.

plan B: failure. i tried tapping out the extractor from the few mm sticking out the back side. no go.

plan C: success! i used my cotter press to press the extractor out! this is illustrated below:

broken bolt with broken extractor stuck inside:
http://farm3.static.flickr.com/2530/4201459216_b097547d3b.jpg

backside of eyelet showing tip of extractor poking through by a few mm:
http://farm3.static.flickr.com/2439/4201457546_f6d814bc07.jpg

cotter press on eyelet. press was too large, so i used a hollow sturmey archer axle nut to take up the slack. extractor popped out without effort:
http://farm3.static.flickr.com/2749/4201586526_6af464cd2f.jpg

next step was to use the dremel grinding bit to route out the hole originally drilled in the bolt for the extractor. i routed all the way to the eyelet threads without destroying them. i was then able to squeeze and collpase the bolt with needle nose pliers to reduce the pressure on the eyelet threads. then i was able to thread it back out! this is how the bolt looked after removal:
http://farm5.static.flickr.com/4046/4200712723_bb4f6e4c96.jpg
http://farm5.static.flickr.com/4007/4201463970_00aa700527.jpg

and finally, the eyelet after major surgery:
http://farm3.static.flickr.com/2509/4200719299_c540c77b46.jpg

the eyelet is a little scuffed now, but it won't be noticeable once the fender stay clamp is bolted in place. the threads are fine, i chased them and a new M5 bolt threaded in perfectly!

thanks to all for your advice!

Congratulations on success.

A little black nail polish will hide the small scuff marks even if the fender stays don't cover everything.

Nice work, your patience paid off.

Hope you were using a good penetrating oil while you were going through the exercise...Magic Mystery Oil is a good candidate. I used to use this on my sail boat in similar circumstances. Sounds like you were trying everything dry. I have removed rusted bolts from friends' bikes and seatposts frozen in place.