Stuck Cotter Pin - Idea Help Sought
 

I just saw the most recent beater challenge and thought back to the star-crossed 1970 Raleigh Record that I picked up for $20 last summer. I was inspired and motivated. I have a fine cotter pin press that I've made good use of on other cranks.

This one bent in the channel - on the drive side naturally. I've tried pushing it back. I've tried putting a ball bearing between the jaws of the press and the butt end of the cotter pin, I've tried a punch and hammer. Reluctant to try a drill, as I don't have a vise or a drill press. Does anyone have a brilliant idea that will get this unstuck, so that I can finish the refurb and get it placed in a new home?

Is the other crank arm still there? Can you ride it? I've read that doing so without the nut dislodges the cotter pretty quickly. Haven't done it myself. The one bike for which I removed cotters did so pretty easily with the socket and huge c-clamp trick, but that won't work with a bent cotter, I suspect.

Air hammer? ;)

I would give the hammer another try. Improvise a way to rigidly support the opposite side of the arm so that the energy is not attenuated. Thread the nut back on a few turns if you can. Give it a good hard blow with the hammer.

One can heat the affected area to several hundred degrees F without doing any damage, even as grease residue is starting to issue a good amount of smoke.


I've removed a few stubborn cotters where heat made the difference. This has never failed me.


Another good way is to drill through the fat end of the cotter with a 3/16" drill bit, this method also has never failed me even after a cotter previously got smooshed from hammer blows.


Some old-time mechanics routinely cut off the cotter's threaded stem with a chisel and then proceeded with a thick drift punch and hammer to get the remains of the cotter out. It requires that the crank be supported above a rigid cement surface with a length of pipe centered on the fat end of the cotter to allow the hammer blows to generate sufficient force.

Riding a square taper crank off is a fairly reliable method.
Never had it work on a cotter.

My normal series of cotter removal...

• Cotter Press (Got the current one from BikeSmith Designs)
• Hammer and punch
• Heat with a torch then try the press
• Heat with torch then try the BFH
• Drill it out from the blunt end

I have been pretty fortunate that I can usually get it out by step 3, I can only recall one in recent years that had to be drilled out. I have never "ridden" one out. Rode one old 3 speed with a sheared off cotter for several years and it never came loose.

Aaron:)

I had my boss' Raleigh with a stuck cotter. Drive side. 3 weeks later, a half a bottle of Kroil, oxy-acetylene heat, air-in-a-can cold, I wound up using a hand drill.

Good luck.

I always used to enjoy a cotter pin challenge (afterward, if successful).

You say that you tried pushing it (the bent part of the cotter) back. If you haven't already done so, try threading the nut part of the way on and giving it a sideways whack with a hammer to straighten the bent section. (If you can't get the bent section sufficiently straight, neither the cotter press nor the hammer and punch will work and you're probably doomed to drilling the pin out.)

Edit: as a last resort before drilling (and only if you've given up on the cotter press), try cutting off the threaded part of the cotter so that the remaining portion is flush with the crank surface and then using the hammer and punch.

If the cotter press doesn't work, it's still worth trying the hammer and punch approach (but don't leave the bike sitting on the floor while hammering; otherwise, the tires absorb a significant amount of the hammer force).

By the way, I always found that pointed punches were unsatisfactory for cotter pin removal: too small a contact point. A solid axle from a rear hub always worked better for me. (For maximum impact, it's best to leave the nut threaded on so that its upper surface is flush with the end of the cotter.)

Supporting the crank arm can help if you happen to have an appropriate small-inner-diameter pipe lying around.

However, since that can still result in a significant amount of the hammer force being absorbed elsewhere than at the end of the cotter pin, I always preferred the opposite approach: hanging the bike from the repair stand's clamp by the tip of the saddle nose so that the bike dangles freely.

Or, if you don't have a repair stand, do what I do and hang the bike from a hook in the ceiling using an inner tube. (It can help to position a couple of chairs against the wheels to keep the bike from swinging around.)

This approach might seem counter-intuitive, but you want to ensure that the absolute minimum amount of hammer force is being absorbed elsewhere than at the point of impact.

I've had success removing the drive side crank with the fixed cup and spindle still attached. Remove adjustable side first. Then carefully remove fixed cup with a wrench behind the crankset.

Once you have the drive side removed (with the fixed cup and spindle still attached), use a drill press to drill out the cotter pin.

I also have a nice cotter press, but it doesn't always work.

The remove first method always works as long as you can remove at least one side of the crank (drive or non-drive side).


Once it is removed, you can also apply brute strength at will.

My Binford impact drill driver air hammer grinder would make short work of that.

Thanks for the constructive ideas.

I am tempted to try riding it off as my preliminary measure (he says looking out the window at snow falling). That said, the bike is otherwise completely disassembled. I forgot to mention that I have sort of a catch-22 situation with the bottom bracket. The crank arm is swaged to the ring, and that makes applying significant force to either use a hammer (to beat out the pin), or a spanner (to get the cup off) an operation that could result in significant lacerations.

If it won't ride off, I think I'll have to puzzle out the removal of the BB as a preliminary step.

Use a large drift (4-6") held over the pin with a pair of vise-grips. No danger to anything but the chainring, if you miss.

FYI, an engineer's hammer has a knurled face, to reduce slipping when it hits a metal forming tool.

Drift Punch.. ball peen hammer.. a carpenters hammer is hard , because nails are soft ,
machinist hammers are softer steel, because the Punches are hardened.


& back up the crankarm against something solid , not sitting on it's tires..

Let us know how it goes!

I'm thinking for those of you with the nice press tool, hindsight being 20/20 perhaps pressing a pin
"in" can be over done. Cotter pins are soft steel and will snug in nice & tight with a couple hammer taps then nutted to spec.

.
...I don't think you'll have much luck riding it off. A cotter, stuck like you describe it, is seated in there well. All the nut does is keep it snugged down, and you've accomplished an alternative to that by bending it.

That said, drilling one out is not a big deal, just PIA, If you can, cut it off even with the crank arm at the threaded end, then center punch it to get a starting point for your drill, Choose a drill bit that is slightly smaller than the cotter itself, and drill it down far enough that you have a nice empty hole to seat a drift or pin punch with an end that is a litle smaller than the hole. Then drip in some ATF/acetone mix on both ends of the cotter, give it a chance to wick in there, and whale on the punch with the crank arm supported on something like a pipe or a notched 2X4 that is supported on a solid surface like a concrete floor. The pin itself is much softer than the the crank arm or the spindle, and you don't really need to go past the spindle intersection with the cotter anyway. Just be careful not to bugger up the hole in the crank arm, which is clearly visible.

I have done six or ten of them this way. LIke I said, PIA, but not all that difficult once you resign yourself to it as the solution.


As a bonus, you can turn the remains of the cotter into a lavalier or a keychain fob. :)

...pulling in a cotter with the nut is a good way to strip the threads. It's almost impossible to "overpress" them on installation if youi want them to stay seated under normal use.

Stuck cotters rank alongside stuck seatposts as the worst of the worst. I had one of these, worked on it for two weeks, every trick I could come up with, and in the end, it still came down to drill, baby, drill. Hard to stay in a zen place when you're swearing so much at the dang thing.

Ditto on a ‘72 UO-8 I just did.

Once you drill it though, stand on both cranks and the drilled pin will shear off.

I've fiddled about with stuck cotters for the last 50 years, and there is no truly foolproof way, but the way that always works for me is to:

1. Remove the mashed, bent, and otherwise unusable threaded end of the cotter. I typically give it a couple swacks with a punch and it breaks off.

2. Take a Dremel and grind a small divot into the approximate center of the thread-end of the cotter.

3. Drill a 3/16' hole about 1/2" deep into the cotter.

4. Punch it out with a 3/16" punch. Use a brass hammer. Always.

This method takes some time, but it has never failed me.

Wait 'til you tackle a rust-welded bottom bracket.

I've never heard this. What special property does a brass hammer have?

I think this is answered in post #14
Better purchase between hammer and drift?

I brass hammer is soft. When you strike cold chisels and punches, you do not risk the chance of shattering the steel. Brass grips. Steel deflects. Its one of the common laws of metalcraft. FWIW, a copper, zinc or lead hammer will do the same, but brass is the most common.