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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 10-05-10, 02:39 PM   #1
Dylansbob
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Advice on a removing crank with rounded bolt

I don't have an attachment to saving the crank arm, so I'm wondering if it would be easier to cut through aluminum than to try to drill out the bolt.
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Old 10-05-10, 03:01 PM   #2
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If you are also not attached to the BB spindle, you could remove the other crank arm and avoid that bolt altogether.

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Old 10-05-10, 03:03 PM   #3
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A picture would go a long way toward fully explaining the situation but you may be able to drill the bolt for an Easy-Out. That might be easier than cutting the crank off.
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Old 10-05-10, 03:09 PM   #4
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You might be able to use a dremel to cut a slot in the bolt head and remove with an impact driver. That is, if you have those tools, and the patience to grind the slot.
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Old 10-05-10, 03:14 PM   #5
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Cartridge BB and unfortunately not a hollow spindle. Everything else on the bike has come out pretty easily. I accidently put my 15mm peanut butter wrench on the bolt before I realized that it was a 14mm bolt. Now it slips with the 14mm socket on it. I started drilling a couple of holes in from the side of the crank arm hoping that I can at least get some WD40 to the actual threads instead of just on the bolt head.
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Old 10-05-10, 03:32 PM   #6
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Originally Posted by Dylansbob View Post
Cartridge BB and unfortunately not a hollow spindle. Everything else on the bike has come out pretty easily. I accidently put my 15mm peanut butter wrench on the bolt before I realized that it was a 14mm bolt. Now it slips with the 14mm socket on it. I started drilling a couple of holes in from the side of the crank arm hoping that I can at least get some WD40 to the actual threads instead of just on the bolt head.
Are you using a six point 14mm socket or twelve point?

Don in Austin
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Old 10-05-10, 03:45 PM   #7
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hammer on a slightly smaller socket, try an sae size. also try 6 or 12 pt
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Old 10-05-10, 04:08 PM   #8
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Take a hammer and mark the center of the bolt with a punch

Drill a hole in the center

Use an extractor to remove the bolt:
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Old 10-05-10, 05:50 PM   #9
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I had a similar issue and found these locally. As long as there's enough space to fit the tool, you can get plenty of leverage on the bolt without concern over tool slippage or breakage.

http://www.mysears.com/Craftsman-Bol...er-Set-reviews
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Old 10-05-10, 05:56 PM   #10
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Also, instead of WD40, use PB Blaster, Kroil, or similar penetrating oil designed to loosen fasteners.
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Old 10-05-10, 09:41 PM   #11
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Ask around and see if any of your friends have a set of 'Metrinch' brand spanners.
They are unique in that they drive on the flats and not the angles of a nut or bolt, allowing you to remove rounded bolt.

Regards,
Roger

Last edited by ramjet1953; 10-05-10 at 09:41 PM. Reason: typo
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Old 10-06-10, 01:17 AM   #12
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Quote:
Originally Posted by Asi View Post
Take a hammer and mark the center of the bolt with a punch

Drill a hole in the center

Use an extractor to remove the bolt:
With the 14mm bolts that are on the cranks. I really doubt that extractor will be able to remove it.

OP: We've removed cranks at the shop where the crank didn't need to be saved - 1 minute with an angle grinder on an AL crank is all that is needed to remove it.
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Old 10-06-10, 10:31 AM   #13
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With the 14mm bolts that are on the cranks. I really doubt that extractor will be able to remove it.

OP: We've removed cranks at the shop where the crank didn't need to be saved - 1 minute with an angle grinder on an AL crank is all that is needed to remove it.
That is just an example.. they come in sizes for removing bolts from M4 (smallest) to M30 (this is some serious stuff!). They have tapered left hand thread that as you turn them into the loosening way it will bite into material of the bolt, wedge itself in, lock into place and for sure it will at some point turn the bolt loosening it. The size of this thing is accordingly to the size of the thread not of the head.

Works every time, I have used it numerous times especially in broken bolts to remove the rest of the bolt still inside. Well that's why it's called a SCREW/BOLT EXTRACTOR
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Old 10-06-10, 10:39 AM   #14
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Extractors are good for removing broken off pieces off pieces of bolts stuck in a tapped hole for some reason, not for removing bolts with stripped heads.

My advice: Drill through the head of the bolt working your way up to a size at or near the diameter of the bolt (5/16" or 8mm) and the head will pop right off as the tension exceeds the strength left in the small amount of bolt cross section left. Don't go any deeper than necessary and you will likely salvage the bottom bracket along with the crank arm. The remaining "stud" in the BB spindle will likely unscrew by hand. Attempting to use an EZ-out on a fully tensioned bolt is a recipe for breaking an EZ-out that offers zero benefit over drilling the head off.
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Old 10-06-10, 10:50 AM   #15
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Either an angle grinder or what Joejack said.

I'll add to that and say if you can find left handed drill bits, use those. They work great for this kind of thing. I've used them at my buddy's shop on numerous car bolts that were stuck.
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Old 10-06-10, 11:25 AM   #16
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Quote:
Originally Posted by Asi View Post
That is just an example.. they come in sizes for removing bolts from M4 (smallest) to M30 (this is some serious stuff!). They have tapered left hand thread that as you turn them into the loosening way it will bite into material of the bolt, wedge itself in, lock into place and for sure it will at some point turn the bolt loosening it. The size of this thing is accordingly to the size of the thread not of the head.

Works every time, I have used it numerous times especially in broken bolts to remove the rest of the bolt still inside. Well that's why it's called a SCREW/BOLT EXTRACTOR
I've used the larger sizes to remove freewheels whose bodies have been damaged so the standard pronged remover no longer engages. You remove the axle, jam the extractor into the freewheel body, clamp in a bench vise and go at it.
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Old 10-06-10, 01:58 PM   #17
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Quote:
Originally Posted by joejack951 View Post
My advice: Drill through the head of the bolt working your way up to a size at or near the diameter of the bolt (5/16" or 8mm) and the head will pop right off as the tension exceeds the strength left in the small amount of bolt cross section left....
This is what I'd do.
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Old 10-06-10, 02:09 PM   #18
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Quote:
Originally Posted by JohnDThompson View Post
I've used the larger sizes to remove freewheels whose bodies have been damaged so the standard pronged remover no longer engages. You remove the axle, jam the extractor into the freewheel body, clamp in a bench vise and go at it.
Do you remember which size(s) you used? I'll have to pick some up in case I run into a similar problem some day (which with my buying habits I'm very likely to). Thanks for the tip!
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