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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 11-29-06, 12:42 AM   #1
xren
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Crank puller tool has threaded the inside of the crank

Completly taking apart my mongoose front and rear suspension mountain bike I came accross no real problems except getting the chain wheel crank off on my two-peiece crank set.

I got the opposing side's lock-nut and everything else out fine but upon screwing the crank-pulling tool into the inside of the crank and then turning the bolt inwards resulting in griping onto the thread and de-attatching it from the axle it gripped onto the thread -and pulled it out.

Lots of metal shavings later I can't even screw the tool into the crank now, there's that little thread.

Now without having to buy specialised tools or whatever else what's the best way to get the crank off? Any help greatly appreciated.
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Old 11-29-06, 05:51 AM   #2
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Was this a hollow pipe bottom bracket? Is it possible that there was a crank bolt washer left in the bottom of the hole. This will result in the crank puller both pushing on and pulling on the crank, thus stripped out threads. If the threads are already stripped, then you might as well just pound the crank off with a hammer and replace it with a new one. Be patient and work at it slowly, you do not want to strip out the bottom bracket shell as well.
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Old 11-30-06, 04:55 AM   #3
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Take it to a bike shop and pay them to remove the crank. No tools needed!

There are (rare) specialised tools to rethread the crank and a ball joint remover or a bearing puller will probably let you remove the crank. Search the archive for details.
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Old 11-30-06, 06:22 AM   #4
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Once the crank is rethreaded, will a new larger crank extractor be required. As I read this post it appears that the threads have been pulled out the front of the crank and the hole is now too large to rethread at the current size? Sounds like the new threaded hole will have to be larger.
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Old 11-30-06, 07:12 AM   #5
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if its a 2 piece external BB unit you dont use a crank puller to remove the cranks. unless you have cranks im not familiar with.
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Old 11-30-06, 01:30 PM   #6
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Quote:
Originally Posted by The Great Stonk
if its a 2 piece external BB unit you dont use a crank puller to remove the cranks. unless you have cranks im not familiar with.
With a title like "crank puller tool has threaded the inside of the crank", I think it's safe to assume it's a square-taper that DOES require a crank puller. Unless of course OP was using the crank puller to file his nails, of course.

The suggestion of re-boring + threading the crank-arm assumes that the cost of this operation plus a new, custom crank puller to service this now-unique crank-arm is cheaper than a new crank-arm.

2 reasonable options:
1. Put the now problematic crankarm back in place, and assume that your ability to service the BB will be quite limited from now on (which may be ok for a while), or
2. Replace the crank arm.

You can do #1 for a long while, and then later #2.
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Old 11-30-06, 01:34 PM   #7
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Sometimes this happens if you don't screw the puller far enough into the arm. This happened to me the first time I removed a crank arm- the screw that torques the arm off in the end was keeping me from screwing the puller far enough in, and when I went to pull it, out came the threading. Really stinks.
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Old 11-30-06, 05:15 PM   #8
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They can helicoil the threads which brings them back to the same size, so you'd use the same puller.
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Old 12-01-06, 05:05 AM   #9
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Thanks for your help. As I wasn't sure of the mechanics I'm a little more clea on what I'm trying to do now.

Quote:
Originally Posted by matimeo
Sometimes this happens if you don't screw the puller far enough into the arm. This happened to me the first time I removed a crank arm- the screw that torques the arm off in the end was keeping me from screwing the puller far enough in, and when I went to pull it, out came the threading. Really stinks.
Hah, thankfully I'm not alone.

Well basically I've already had to replace the other crank and due to other advice tried to "bash" this crank off using a mallet, hitting against the chainwheel (yes this crank is now totally ruined and I'm willing to replace).

To those who asked, yes the end of the axle is square to which the crank is pushed onto, really hard. I have tried levering it and have hit the chainwheel so hard it's bent out on not far from a 45 degree angle.

Should this require this much force? It's kind of frustrating to be pounding the absoloute **** out of this and not be getting anywhere. I'm not just smacking the chainwheel either, the way I'm hitting it I'm still applying a huge ammount of out-ward force.

So what's the best advice when you have no regard for the condition of the crank? Is persistance the key, because I'm not sure if I've even moved it, I'm just trying to get a benchmark for how much force this is actually going to take.
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Old 12-01-06, 10:36 AM   #10
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When you hit it you rotate it against the taper and jam it. You may be able to drive it out eventually by hitting it alternately on opposite sides, making it rock on the taper.

But the best way to do it is to use an automotive gear puller.
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Old 12-01-06, 12:33 PM   #11
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Ouch, you've ruined the crank then?

Try this. Find a socket that just fits completely inside the square of the crank arm. Stand the socket on a concrete floor. Position the bike over the socket so the socket is inside the square of the crank arm. Have someone hold the bike in that position.

Use a long flat end punch and a 2.5 lb hammer to hammer the crank off. Be sure to hit the crank arm as close to the axle as you can. If you are worried about cosmetics, put a very large flat washer between the punch and the crank arm to prevent marring.
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Old 12-01-06, 01:55 PM   #12
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socket, punch and hammer sound like it would work. I had a fit one time when the threads were worn on one of my crank arms. here is what worked for me. clean both the crank threads and puller threads super good with a solvent like denatured alcohol. apply some epoxy to the threads and turn in the puller body. let it set a few hours. 24 is best. proceed as normal with the removal. gently heat the crank arm with a propane torch, the glue will soften and the puller with turn right out. Gentle is the word of the day. Unlike steel, aluminum doesn't get red hot as a warning before it melts. You shouldn't be getting it anywhere near that hot though. you should be able to hold the crank in your hand with a potholder and get the job done.
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Old 12-01-06, 04:59 PM   #13
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Quote:
Originally Posted by San Rensho
Ouch, you've ruined the crank then?

Try this. Find a socket that just fits completely inside the square of the crank arm. Stand the socket on a concrete floor. Position the bike over the socket so the socket is inside the square of the crank arm. Have someone hold the bike in that position.

Use a long flat end punch and a 2.5 lb hammer to hammer the crank off. Be sure to hit the crank arm as close to the axle as you can. If you are worried about cosmetics, put a very large flat washer between the punch and the crank arm to prevent marring.
+1

Back in the day we used to remove the bolt, and hit the crankarm with a hammer to get her it off. Put a towel or something over the crank arm to protect from cosmetic damage.
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