Mashed cotter: what now?
 

Hi. So, I totally know better than to do what I did, but I did it anyway. :mad: Using my BikeSmith cotter press, I got impatient and badly mashed a crank cotter. Now it's not straight, so I'm not sure how to push it out, or how to straighten it so I might be able to. What would you do next?


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Some penetrating oil, then brute force with a block of wood and a hammer.

Ooh...nevermind, just saw the pics..ouch

Drill it out.

Go slow. Start with a small diameter bit. Work your way up.

And hopefully obviously, drill it out from the non-threaded side.

Try straightening it with a hammer and drift punch. It may break off. If it does, drop a ball bearing or two in the hole so the press has something to push on when you extract the remains.

Grind the threads down to the crank arm (CAREFULLY) then whack it with a hammer and punch dead center. Often the heat of grinding is enough to break the bond. THis technique has worked with nearly every bent cotter I had to deal with. New cotters are available from J&B at your LBS. Most likely a 9mm "English" diameter.,,,,BD

+1 on the grind !!

If you go banging away with any lateral force to straighten, you may screw up more stuff....like bearings and races, and a slip/miss could be ugly !

Have patience and good luck,

Joe

I've had good luck drilling these.

+1, this is better than grinding I think, less chance of marking up the crank. Plus the bend looks to originates below the crank surface, so you'de only end up with a short bent cotter. A few blows from a drift punch will usually snap it off below the crank surface, than you can begin with the press again. If you resort to wacking it with a hammer, be sure to back it up with something so that the BB doesn't take the force of the blow.

I had this happen recently as well, and ended up just taking the hacksaw (I need to get a grinder!) to what was sticking out of the hole - left about 1mm between the end of the cotter and the crank arm, worked really well because they are super soft material. That gave a nice flat spot on the end of the cotter - which provided a nice surface to hit it with a punch a few times, then break out the drill. I ended up drilling to 5/16 before getting the pin to budge - but mine had also been in there since 1972 (or at least I am pretty sure it was anyway).

I just took my ride to my lbs because I was afraid of doing this very thing. Best of luck with the pins.

If you give it a few good smacks from the other side, tht should give you a mm or 2 to go in with the hacksaw and saw off the bent part. Then get a drift and give it one hard, hard hit with the hammer to drive it out.

Drill, baby, drill.

I'm betting that it's going to break off. Once it does, the ball bearing suggestion is a good one that I've also found successful.

Use a cutoff wheel in a circular saw to get through the spindle; throw heavy unnecessary weight away. Install a square-taper spindle and alloy cranks.

Haha! True CB!

Genius. I'll call it the DL-2.

If you *need* to preserve the cottered-crank character-- and I can see why one would, the cottered units are very elegant-- any bike kitchen or co-op has a plethora of spindles and cranks lying around for cheap or free. Not many people want to, or even know how to, deal with them. But if you can't get the old ones off easily, don't waste time. Finesse is fine, but sometimes brute force gets the job done with less hassle.

If you can't find new-to-you cottered cranks, they are a glut on eBay.

Sounds like a plan. Will a grinding wheel on a handheld drill be sufficient, or will this require heavier artillery?

Got here to late to offer the same excellent advice posted by others, but would certainly like to know how this turns out for you. Success stories are great.

-G

I didn't saw the spindle (thought about it though!), but I did install a square taper and alloy cranks to eliminate this problem in the future... and lose a nice little bit of weight too!

You can probably grab the bent end of the threads with a vise-grip and bend it back and forth enough to break it off. Then drill a hole into the center of it, from that end. Then get the Harbor Freight "Heavy Duty Chain Breaker" tool for about ten bucks and drill out the receiving end of that so it fits over the cotter head. Now screw the pushing end of said tool down and watch to make sure the thin pin of the chain breaker goes straight into the hole you drilled. Snug the coarse threaded part down as far as possible, then tighten the fine threaded part. Magic!

I know this sounds complicated, and some of my description won't make sense until you have the tool in hand, but this technique is guaranteed to work and will not damage your crank in the least. If you want to pay shipping, I'll even lend you my Harbor Freight tool, which has already been modified (but it'll be cheaper just to order one yourself).

Be sure to get your replacement cotters from the same place that you got your press. His really are better.

Such a fuss! My cotters just drop out once the retaining nut is removed. :rolleyes: