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Old 05-04-08, 03:27 PM   #1
thekauz
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Am I screwed??

I was taking the pedals crank arms off my bike to service the bottom Bracket. While using the pedal extractor tool I boogered up the drive side threads where the extractor screws in.
The other side is fine and I can get all back together but I wouldn't mind being able to get that crank arm off at some point.

Its aluminum but can it be rethreaded?

Any tricks to get the crank arms of the bottom bracket spindle??

Thanks
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Old 05-04-08, 03:48 PM   #2
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It can't be rethreaded to the same thread to fit the crank extractor again so you are hosed as far as restoring it to it's previous state. There are gear pullers and similar devices that will pull a crank arm with bad extractor threads but they are a pretty crude approach.

Reassemble the crank and bottom bracket now and plan on a new crank when you have to take it apart in the future. Sorry.
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Old 05-04-08, 03:56 PM   #3
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Based on my own personal rich experience, "YES, you are screwed".

You can try to use some gasket tape from the hardware store that they use on threaded pipe, but the best you can hope for is to get the crank arm off. I wouldn't put it back on and expect to be that lucky next time. I suppose you could have a good welder build up the aluminum, drill, and re-thread it, but unless it is a tech-school project with great tools and free labor, you are better off buying a new crank arm.

So, what to do next? You don't want to try to hammer the crank arm off. That is very likely to damage your bottom bracket.

The best solution I found was to use a disc cutter on my hand-held drill and cut the crank arm off. It isn't too difficult. You want to make sure that you don't cut the BB spindle (axle) when you cut the crank arm. I just cut down until it was very close and then use a big fat screw-driver wedged into the cut groove and a tap of a mallet to crack the remaining uncut aluminum near the spindle. Once you do that and spread the crank hole, she should slip of easily.

Does it suck? Ooooh Ya!
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Old 05-04-08, 04:11 PM   #4
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Borrow a gear/wheel puller from a buddy who works on cars. It is a crude approach, but it will work. Far better than hammering it off, or cutting it off.

Depending on what the future holds for this bike (how many miles you plan to put on it, how expensive it is), you could put it back on. But the next time will present the same problem.

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Old 05-04-08, 04:36 PM   #5
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Here's something you may want to try, especially if it's a square taper spindle, before resorting to a puller-type tool: turn the bike on its side and dribble some penetrating oil between the spindle and crank arm. Tap on the spindle to help it penetrate. Let it sit for a few hours. Next, partially install the crank bolt leaving about 1/8" unthreaded. Go for a ride. If you're lucky, the crank will break free while you're riding.
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Old 05-04-08, 05:06 PM   #6
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Next, partially install the crank bolt leaving about 1/8" unthreaded. Go for a ride. If you're lucky, the crank will break free while you're riding.
Next step: discard the now removed crank. This approach will indeed remove a crankarm but it will hog out the square taper recess in the crank arm which will NEVER stay tight on the bb spindle again.
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Old 05-04-08, 05:39 PM   #7
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Next step: discard the now removed crank. This approach will indeed remove a crankarm but it will hog out the square taper recess in the crank arm which will NEVER stay tight on the bb spindle again.
I thought the crank arm was already buggered and the OP was merely trying to remove it for replacement. If this method works it saves you from using a gear puller which can mar up the arm pretty bad. If your goal is to salvage the crank arm without going through the same ordeal the next time you want to remove it, I can't think of a non-desctructive method.
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Old 05-04-08, 06:11 PM   #8
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How did you "booger up" the threads. It's important. Did you not thread the nut section of the tool all the way in resulting in stripping the first one or two threads on the crank, did you cross thread? Please explain.
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Old 05-04-08, 06:46 PM   #9
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How did you "booger up" the threads. It's important. Did you not thread the nut section of the tool all the way in resulting in stripping the first one or two threads on the crank, did you cross thread? Please explain.
I don't know how the OP buggered up his threads, but I can tell you that I have done it too.

I was VERY carefull to get the threads lined up correctly and put the crank puller into the crank threads as far as it would go. I guess the crank was just on the spindle way too tight (maybe steel/aluminum bonding?). Anyway, I turned the crank puller handle slowly, slowly, and it got harder to do, and I put a little more muscle into it.... and it started to feel like the crank was pulling off as it should - you know the feeling when turning the puller handle gets easier and easier. Then you see the shiny aluminum on the threads of the crank puller and you say to yourself,.... "I'm screwed!"
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Old 05-04-08, 07:54 PM   #10
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Quote:
Originally Posted by Toyman991 View Post
I thought the crank arm was already buggered and the OP was merely trying to remove it for replacement. If this method works it saves you from using a gear puller which can mar up the arm pretty bad. If your goal is to salvage the crank arm without going through the same ordeal the next time you want to remove it, I can't think of a non-destructive method.
The OP has stripped the crank puller threads but the square taper is still ok. If he can get the crank off with a gear puller or "pickle fork" the square taper can be reused at least once more even if the exterior is a bit messed up.
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Old 05-04-08, 08:01 PM   #11
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+1 borrow/rent a pulley puller from an auto mechanic, it can pull the crank with no problem.
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Old 05-04-08, 09:03 PM   #12
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I don't know how the OP buggered up his threads, but I can tell you that I have done it too.
Yup, when I first got into C&V bikes. I was removing a crank to clean and lube a 1980's BB. I turned the Park crank puller handle at the same rate as the nut part of the tool that screws into the crank. When I felt everything snug up, I started cranking on the bolt section to put pressure against the BB and pull the crank. Sure enough, I did not have the tool fully inserted in the crank and stripped the two outer threads. I decided to clean and re-install the tool, this time I put the section that screws into the crank in all the way, you know, the way your supposed to do it. Between the inner threads and what was left of the two outer threads on the inside of the crank, to my relief, I had no trouble pulling the crank. That's why I posted. I wanted to find out if the OP stripped all the threads, most of the threads, or just one or two of the outer threads. I know its an outside shot, but its worth a try.
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Old 05-04-08, 10:00 PM   #13
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Man, I hope it's not as stuck as the one a friend and I ran into a while back. The gear puller started threading itself into the crank bolt threads. The taper part never budged. This was after the threads
pulled out of the crank. He finally ended up leaving the crank on the bike. We think it may have been put on with an impact wrench.,,,,BD
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Old 05-05-08, 06:04 AM   #14
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...I can't think of a non-desctructive method.
I can. Aluminum expands and contracts more than steel for a given temperature gradient.
  • Remove the bolt.
  • Lay bike on side, damaged crankarm up.
  • Pack the end of the crankarm in dry ice (any ice cream shop will have it, use heavy gloves to handle it).
  • Let sit for 10 minutes.
  • Heat the end of the crank arm. (Not hot enough to burn yourself, but significantly warm to the touch.)
  • Lift on the crank and tap a few times on the end of the spindle (not hammer, tap).
  • Repeat.

The cyclic contraction and expansion will walk it off, or get it loose enough that a few light taps will free it. You will probably have to repack the bottom bracket bearings, becasue the heat will tend to make the grease flow out.
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Old 05-05-08, 06:39 AM   #15
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Maybe the problem is just with the first few threads...if you clean and correct the first threads maybe the extractor will find a "bite" on the back threads. You need to be sure to back the bolt out of the extractor all the way to be sure you get all the access possible before trying to remove the crank.........
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Old 05-05-08, 03:19 PM   #16
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I'll Try the Easy way first

Thanks for all the advice guys, I'll try the easiest way first and go progressively "tougher" until it come off (so good).
Any one know who has a good hybred bike crank with 175mm cranks and a square taper?
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Old 05-05-08, 06:37 PM   #17
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Any one know who has a good hybred bike crank with 175mm cranks and a square taper?
Here's a good one:

http://www.sheldonbrown.com/harris/cranks/11074.html

Here's a cheaper one:

http://www.biketoolsetc.com/index.cg...em_id=SU-FCM32
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Old 05-05-08, 08:34 PM   #18
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Similar situation

I just bought a used MTB frame and got the still installed XT crank arms and BB for just $20. The person I bought the frame from was trying to strip the frame down and was trying to take the crank arms off and couldn't do it. When I took it home I clearly saw that he had left the crank arm BB bolt in. It wasn't obvious to him because both the BB and the crank bolt are hollow. Anyway I thought that since just the first two threads are ruined maybe I could get a bottom tap (flat ended tap) and run it down into the crank arm to clean up and rematch the threading. Has anyone done this before? Does anyone know what the threading is for the crank arm removal threads? I could go to the hardware store and try to match the threads using the removal tool but I thought maybe someone here already knew the thread sizing??? I'm of course hoping to restore the full usability of these bargain cranks.
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