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Ruined allen socket head on a crank bolt. How to remove?



 
 
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  #1  
Old September 11th 04, 11:53 AM
Michael Slater
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Default Ruined allen socket head on a crank bolt. How to remove?

The bottom bracket of my Trek Liquid 20 is making a cracking noise. My
first guess, and the Barnett Guide's advice is that it's most likely a
loose crank. (This has happened to me before on other bikes).

Today I decided to remove the cranks and then re-tighten them. In
preperation, I even bought a torque wrench so that I can tighten the
cranks to the correct specification.

Not thinking clearly, I removed the cranks from the wrong Liquid 20.
Didn't really matter, I'll regrease and re-tighten them too. But then
I realized I'd made another mistake. When I bought the torque wrench I
forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key
is needed to remove the crank bolt that holds the crank tight against
the splines of the bottom bracket. This precludes me from retightening
the cranks to the correct torque.



Oh well, I might as well remove the cranks from the second (creaking)
bike. First one came off fine. The second one was a serious nuisance.
For some reason I couldn't get good purchase and it wouldn't budge.
Then I noticed that the allen wrench was slipping. Before long I can
see that the allen key head of the bolt is rounded off and I can't get
any purchase on the bolt. It's stranded. I'm screwed.

I took the bike to a local bikeshop that seems happy to get down and
dirty. After I refused the guy's offer to "do a total rebuild of the
bike -- take it all apart put it all back" (it doesn't need it) I
think he grew cold on me. And when I came back thirty minutes later
said it was impossibly stuck and my best bet was to chisel it out. For
heaven's sakes.

I've seen references to adjustable pin spanners, but the torque
necessary to break free the crank bolt from the bottom bracket is
immense. I can't imagine them standing up to the task.

So two questions?

1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.

2) Where do I find a replacement crank bolt?



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  #2  
Old September 11th 04, 02:49 PM
Mr. Bill
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Default

stuck bolt, yuck:

consider this as last ditch desperation advice, unless someone with more
than half a brain supports it:

take the bike to a reputable auto repair place, ( i would take it to
someone that specializes in bmw, but thats just cause i have found they
all seem to really know thier stuff )

have them use the mig welder and weld a nipple on the end of the screwed
screw. this will allow you to use a pair of vice grips to spin it with
the advantage that the heat transfer into the bolt will help break it
free from being seized.

this is comonly done in engine blocks and etc when you break a head
bolt. the heat transfer to the bottom bracket spindle and the crank
should be miminal, as MIG is used when welding heat treated metal
without taking the temper out of it.

Mr. Bill


Michael Slater wrote:
The bottom bracket of my Trek Liquid 20 is making a cracking noise. My
first guess, and the Barnett Guide's advice is that it's most likely a
loose crank. (This has happened to me before on other bikes).

Today I decided to remove the cranks and then re-tighten them. In
preperation, I even bought a torque wrench so that I can tighten the
cranks to the correct specification.

Not thinking clearly, I removed the cranks from the wrong Liquid 20.
Didn't really matter, I'll regrease and re-tighten them too. But then
I realized I'd made another mistake. When I bought the torque wrench I
forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key
is needed to remove the crank bolt that holds the crank tight against
the splines of the bottom bracket. This precludes me from retightening
the cranks to the correct torque.



Oh well, I might as well remove the cranks from the second (creaking)
bike. First one came off fine. The second one was a serious nuisance.
For some reason I couldn't get good purchase and it wouldn't budge.
Then I noticed that the allen wrench was slipping. Before long I can
see that the allen key head of the bolt is rounded off and I can't get
any purchase on the bolt. It's stranded. I'm screwed.

I took the bike to a local bikeshop that seems happy to get down and
dirty. After I refused the guy's offer to "do a total rebuild of the
bike -- take it all apart put it all back" (it doesn't need it) I
think he grew cold on me. And when I came back thirty minutes later
said it was impossibly stuck and my best bet was to chisel it out. For
heaven's sakes.

I've seen references to adjustable pin spanners, but the torque
necessary to break free the crank bolt from the bottom bracket is
immense. I can't imagine them standing up to the task.

So two questions?

1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.

2) Where do I find a replacement crank bolt?



  #3  
Old September 11th 04, 03:16 PM
Woogoogle
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Default

Would welding heat up and destroy everything in the area? How about
drilling out the bolt head, removing the crank and then using a
gripvise on what's left of the bolt. You probably would mess up the
crank a bit when drilling out the head.


(Michael Slater) wrote in message . com...

So two questions?

1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.

2) Where do I find a replacement crank bolt?



  #4  
Old September 11th 04, 03:24 PM
Derek Hodges
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"Michael Slater" wrote in message
om...
The bottom bracket of my Trek Liquid 20 is making a cracking noise. My
first guess, and the Barnett Guide's advice is that it's most likely a
loose crank. (This has happened to me before on other bikes).


I've seen references to adjustable pin spanners, but the torque
necessary to break free the crank bolt from the bottom bracket is
immense. I can't imagine them standing up to the task.

pin spanners are commonly used on cup and cone bottom brackets. I wouldn't
count that option out.

--
Derek Hodges
Toronto


  #5  
Old September 11th 04, 03:40 PM
Mr. Bill
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Woogoogle wrote:
Would welding heat up and destroy everything in the area?


MIG welding doesnt use any flame so the heat is extremely localized.
my guess is the crank wouldnt heat up much at all, and would not become
hot enough to burn your fingers

the heat will only to into the bolt directly, although some will be
transferred to the bottom bracket spindle and the crank but not that
much.

Mr. Bill


  #6  
Old September 11th 04, 03:48 PM
Sheldon Brown
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Michael Slater wrote:

Oh well, I might as well remove the cranks from the second (creaking)
bike. First one came off fine. The second one was a serious nuisance.
For some reason I couldn't get good purchase and it wouldn't budge.
Then I noticed that the allen wrench was slipping. Before long I can
see that the allen key head of the bolt is rounded off and I can't get
any purchase on the bolt. It's stranded. I'm screwed.


1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.


I once ran into one of these that had been wrecked by a worn-out Allen
wrench. In the end, I used a tool commonly known as an Ezy-Out, or
generically, as a "screw extractor." This is a tool that looks sort of
like a left-hand threaded tap, with tapered helical grooves.

The normal way to use an Ezy-Out is to drill a specific sized hole into
the bolt then insert the Ezy-Oyt. However, I didn't believe that an
Ezy-Out skinny enough to fit into the bolt shaft would be strong enough
to undo this particularly recalcitrant bolt. I also didn't relish
trying to drill out the bolt.

Instead, I used a considerably larger Ezy-Out, the biggest one that
could fit into the remains of the 8 mm Allen socket. (Sorry, I don't
recall the specific size.) The Allen socket is not so deep, so the
largest size that would fit in was too loose to even get close to
getting a grip.

I got around this problem by grinding the point of the Ezy-Out off. You
need a serious bench grinder for this, and it is important to quench the
Ezy-Out very frequently in water so it doesn't overheat and anneal the
hardened steel it's made of.

This took a while, but in the end it worked.

2) Where do I find a replacement crank bolt?


Any bike shop.

Sheldon "Sparky" Brown
+-------------------------------------+
| Don't drink and drive: you might |
| hit a bump, and spill your drink! |
+-------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

  #7  
Old September 11th 04, 07:44 PM
Zog The Undeniable
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Michael Slater wrote:

The bottom bracket of my Trek Liquid 20 is making a cracking noise. My
first guess, and the Barnett Guide's advice is that it's most likely a
loose crank. (This has happened to me before on other bikes).

Today I decided to remove the cranks and then re-tighten them. In
preperation, I even bought a torque wrench so that I can tighten the
cranks to the correct specification.

Not thinking clearly, I removed the cranks from the wrong Liquid 20.
Didn't really matter, I'll regrease and re-tighten them too. But then
I realized I'd made another mistake. When I bought the torque wrench I
forgot to get a 3/8" square to 8mm allen key socket. The 8mm allen key
is needed to remove the crank bolt that holds the crank tight against
the splines of the bottom bracket. This precludes me from retightening
the cranks to the correct torque.



Oh well, I might as well remove the cranks from the second (creaking)
bike. First one came off fine. The second one was a serious nuisance.
For some reason I couldn't get good purchase and it wouldn't budge.
Then I noticed that the allen wrench was slipping. Before long I can
see that the allen key head of the bolt is rounded off and I can't get
any purchase on the bolt. It's stranded. I'm screwed.

I took the bike to a local bikeshop that seems happy to get down and
dirty. After I refused the guy's offer to "do a total rebuild of the
bike -- take it all apart put it all back" (it doesn't need it) I
think he grew cold on me. And when I came back thirty minutes later
said it was impossibly stuck and my best bet was to chisel it out. For
heaven's sakes.

I've seen references to adjustable pin spanners, but the torque
necessary to break free the crank bolt from the bottom bracket is
immense. I can't imagine them standing up to the task.

So two questions?

1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.

2) Where do I find a replacement crank bolt?




Get a stripped bolt extractor kit ;-)

Basically a hardened screw with a left-hand thread. Drill a small hole
and screw the tool in. The bolt will come out.

Replacement crank bolts are widely available in aluminium, but these are
useless for actually fitting cranks (they work OK for holding them in
place once they have been torqued up with a steel bolt). Anyway, the
good news is that most bottom brackets use standard M8 threaded bolts,
so you can use one of those (with a suitable washer to protect the
crank), fit the crank, then remove and replace with the alu bike jewellery.
  #9  
Old September 11th 04, 08:24 PM
Werehatrack
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On Sat, 11 Sep 2004 19:44:58 +0100, Zog The Undeniable
wrote:

...Anyway, the
good news is that most bottom brackets use standard M8 threaded bolts,


Ahem. M8 fine thread. That's M8x1.0 The more common size of M8 is
the M8x1.25, which most hardware stores have. I have found few
hardware stores in the US have 8x1.0 stuff, but far too many of them
have brain-dead staff who will look at the bolt and incorrectly
identify it as 5/16NF, which it closely resembles. Buying this bolt
at the lbs is a good idea in my opinion.

so you can use one of those (with a suitable washer to protect the
crank), fit the crank, then remove and replace with the alu bike jewellery.


Eh, I suppose, but I figure that substance overrules form, so I just
go with the appropriate steel bolt and knock the plastic cap in to
cover it.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
  #10  
Old September 12th 04, 01:06 AM
Chalo
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Sheldon Brown wrote:

Michael Slater wrote:

Before long I can
see that the allen key head of the bolt is rounded off and I can't get
any purchase on the bolt. It's stranded. I'm screwed.


1) How do I get this bolt out? Currently my only idea is to have
someone weld a socket directly on the bolt that I can torque free.


I once ran into one of these that had been wrecked by a worn-out Allen
wrench. In the end, I used a tool commonly known as an Ezy-Out, or
generically, as a "screw extractor." This is a tool that looks sort of
like a left-hand threaded tap, with tapered helical grooves.


Another approach would be to drill out the socket with a drill at
least 8mm in diameter (preferably a little bigger) until the bolt head
comes off the thread. After the fastener's tension is released, the
stub remaining in the spindle should turn out with no significant
torque required.

Left-handed drill bits are especially good for this because they tend
to spin the fastener out as soon as the tension releases.

Chalo Colina
 




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