removing seized cranks - square taper

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removing seized cranks - square taper

Postby scottyj » Sat Mar 08, 2008 9:46 pm

If anyone has any ideas, I am all ears. I have acquired an nice old reynolds racing frame, but there are a set of shimano 600 cranks on it that refuse to budge. Have already stripped threads in crank arms.

I have tried using penetrating oil, freezing shaft and using a 3 armed puller all to no avail. only step left is to take a gas torch to the crank arms, something I was trying to avoid.

Please, someone must have the knowledge.

Scott J. Cairns
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by BNA » Sat Mar 08, 2008 10:50 pm

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Postby Whitz End » Sat Mar 08, 2008 10:50 pm

You might be able to fit a blade in between the BB shell and the crank arm and cut the spindle?
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Postby Kid_Carbine » Sun Mar 09, 2008 2:00 am

The chances of you cutting through a B/B axle with a hacksaw in a lifetime are somewhere between slim & none.

For tight ones I pour a lot of boiling water over the crank first with some tension screwed on. This makes the alloy grow a whisker, reducing the tension, or the grip, on the square shaft.
A hair drier with some restriction to the incoming airflow will also heat up the crank at the B/B axle, but it must be heated right through the alloy at this point to do any good.
I have no idea how one can freeze the steel B/B axle shaft, making it shrink, without freezing the alloy crank at the same time. Aluminium transfers heat more quickly than steel & reacts to changes in temperature much more, so it would shrink onto the shaft even faster & tighter. Freezing also kills the lubricating qualities of whatever might still be in there.

Unless you particularly want to save these now useless cranks, the only thing you can do is to destroy the cranks at the axle taper to make them release their grip.

Depending on the tools that you have, one method is to drill straight into the crank from the edge. The idea is to weaken the alloy crank arm at the boss & make it split, thereby releasing its grip on the axle. You can use one larger hole &/or several smaller holes across the boss, as long as it is weakened enough to split it right through to the square hole, even if it takes an assist from a cold chisel to split it.
If possible, drill straight into a point of the square shaft as this reduces the drilling distance & this corner is a high stress point, so it should split more easily. [we hope]

If this is done from the side of the crank & it still won't come, then it can be done from the other side as well allowing removal of half of the boss. Now THAT will do it.
At least this way you should be able to save the axle.
Carbine & SJH cycles, & Quicksilver BMX
Now that's AUSTRALIAN to the core.
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cranks

Postby scottyj » Sun Mar 09, 2008 2:22 pm

I am not quite ready to call it quits yet but will still keep working on the heating theory. I am far too tight to buy another set of cranks. Will try the hot water theory and the hair dryer today. Will use 3 legged puller with a backing plate to pull it off.

If that fails I will be off to the tool shop for a special heat applicator, as these do exist and I will sure as heck be using it again some day.

Will post the outcomes. Thanks very much for your help.

Scott J
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Postby Mulger bill » Sun Mar 09, 2008 7:53 pm

Try riding with the crankbolts out Scotty.

Shaun
...whatever the road rules, self-preservation is the absolute priority for a cyclist when mixing it with motorised traffic.
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crank solution

Postby scottyj » Mon Mar 10, 2008 1:49 pm

Please note that these cranks were really, really stuck on. I think persistantly worrying the joint did it in the end. Persistence!!

Well, I finally got one off (drive side) and expect other to follow soon. I didn't go with the riding them off approach (with bolts out) as I expect this would have resulted in rounding out the cranks anyway, unless you stopped to check all the time.

I went with the very helpful suggestion of hot water. One jug did the trick. Could not use crank puller because already stripped. Found that an old cold chisel worked as an effective lever, levering off edge of bottom bracked. Just kept working it around and then gave a bit push and Bang...of it came.
Scared the crap outa me. "what was that...oh..theres the crank on the ground...hooray".

I am going to try to reuse them and put in a kit to fix up the ruined internal threads. Just can't stand to throw away a pair of cranks.

Hope this helps someone else.
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Postby Andrew Grace » Tue Mar 11, 2008 12:52 pm

When I did mine recently, the drive side came off easily using a crank removing tool.
The non drive side was harder. I used a mini blow torch on the alloy crank, I kept moving the torch so as not to damage the crank. This combined with crank removing tool did the trick.
So you can use a flame on the crank, just be carfull.
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