mparker326

I am terrible at this and would like to know some pointers/techniques.

1. What file do you use?
2. What do you hold the pins in and what orientation?
3. How do you know what angle you need?
4. How do you measure the angle?

Signed, one whose crank arms are not 180 degrees apart or one who has given up and converted to a 3 piece crank.

Salubrious

If the cotter pin needs filing, the first thing you will notice is it does not go all the way through the hole on the crank so that you can properly pick up the nut on the other side (don't forget the washer when checking this).

So that is where you start- to change the angle of the flat spot on the cotter, such that you get the appropriate amount of threads exposed once installed. Keep in mind that to install the cotter, a press should be employed. The nut is not to be used to apply the pressure of installation. Its there to keep the cotter in place once installed.

So its handy to use the press to see how much thread you actually have exposed when fitting it to the crank because you will likely have to install and remove the cotter pin a few times to achieve a proper fit.

Now the problem with this approach is that you don't get exactly 180 degrees out of the crank, but you can get really close such that you can't tell if you are simply careful. So how I would do it would be to file one cotter such that I get a good fit, then measure from the fat end (the end opposite the nut) to see how much you had to file the part, and then mark the second cotter such that you file it in exactly the same way. If you are careful and have a good machine scale it will work fine. A dial caliper is nice but not mandatory.

I just mount the cotter pin in a small vise and have at it. A medium bastard (flat) file should do the trick. Best to file too little rather than too much

Really, the thing you want is that cotter press. If you have one, you will really wonder how you got along without it. Bikesmith makes a pretty good tool at a reasonable price and I have used it on British three speeds, but also nicer cranks like Chater Lea, Stronglight and Campagnolo:

New Crank Cotter Press

Good Luck- have fun!!

auchencrow

Starting with the appropriate (English, French, Italian) cotters, I do an initial assessment of how much I need to file by seating the cotter in the crankarm/bb assembly. Depending on how much protrudes, I resolve to file more or less.

I use a large (12") good quality Mill file with a bastard cut (excuse my language! ) and a bench vise with good square jaws, such as will allow a good grip on the cotter.

My objective is to effect a completely flat face, maintaining the same angle as was extant on the cotter from the manufacturer. This will yield full faced contact to the bb, and maintain alignment of the crank arms to each other.

I try err on the conservative side filing less rather than too much, but generally going back at it with the file a second time is where I mess up, in which case I have to start over with a new cotter.

After you mess up a lot, you'll get better at it too.

photogravity

If you can find one of these, they are even better:


Park CR-2 Cotter Press Tool by Sallad Rialb, on Flickr

FBinNY 

Filing should br the rare exception rather than the rule. Cotters come milled in various diameters, and the standards ahven't changed all that much over the years. The key is to replace BOTH cotters with a matched pair from the same box. Replacing a single cotter is purely a crap shoot even if you try to match the angle.

Years ago (many years ago) they used to offer cotter filing jigs which were basically a clamp with a long shallow bore. They allowed filing to a consistent angle, and you controlled the depth by how far along the sloping hole you positioned the pin. Once the pin was clamped you filed flush to the top of the jig.

Here's a sketch of an improvised jig you can use to deepen the flat. With some creative improvisation you can do something similar to set a different angle (should you need to)


Minor correction, you don't have to match the depth of the angle cut, only the angle itself.

photogravity

Pretty much the way that auchencrow and Salubrious describe the process is the way I try to approach installing new cotters. The only other thing I might add is that if you have the cotters that came out of the arms, they can, though not always, be useful for making a comparison on the replacement cotters. As already mentioned, it's better to be conservative and not take too much material off the cotter.

BTW, where do you get the idea that need to have your cranks 180° apart? I would venture to say there are plenty of folks with cottered cranks that are a couple degrees apart and don't even notice it. I'm probably even one of those people.

auchencrow

The problem these days is that good quality cotters are like hen's teeth and the cheap cotters don't have flat faces.
The so-called "flats" are rounded such that so they don't seat well, and tend to allow just point contact with the bb.
This is why I always reface/file cotters - even if it's only a little to reface the flat, to get a better bite with the bb.
(Of course maintaining the same angle as was extant on the cotter from the manufacturer is still essential for the aforesaid reasons).

FBinNY 

Back when cotters were SOP (an era lasting almost a century), most pros, and just about all non pros, installed cotters by hammer. It's an easy job requiring nothing more than halfway decent hammer skills (can you drive a nail without bending it?) and the awareness of the need to support the crank arm, which is the key to success. Testing the angle is especially easy with a hammer, because you'll only TAP it home (no need to support the arm yet), and can easily tap it back out undamaged.

For my part, I have never failed to remove a cotter cleanly and easily with a hammer. In most cases I could even get them out without damaging the threads.

photogravity

That's why I get mine from Velo Classique. He sells high grade cotters, not the cheap junk others sell.

randyjawa 

Hard to explain, but here goes...

Use a magnet to hold the flat of the cotter. Clamp the cotter, still held by the magnet, into a vise. Before snugging the vise, ensure that there are two spacers, one each side of the cotter and flat to the top of the vice jaws. The shims should be roughly ten thousands of an inch thick.

Once clamped in the vice, remove the magnet and the shims. Now the flat of the cotter pin will be sitting, parallel to the top of the vice jaws and ten thousands of an inch high. Simple file the cotter flat even with the vice jaws and, voila, control angle and amount of cut (removed portion) completed. NOTE: Your file will do little damage to the hardened vice jaws and you will know when you are done filing.

Try the cotter, and, if necessary, repeat the above procedure. You will end up with two identical angles and parallel crank arms, with the cotters properly fitted. Now, press them into place with that fancy press, or build up what I use for next to nada...

rhm

To measure the angle, I place two cotters together, flat to flat, threads opposed, and measure the total thickness at various points. If the angles of the cotters are complimentary, the outer edges will be perfectly parallel. It doesn't really matter if the angles are exactly the same, as long as they are complimentary.

ursle

9.5 mm pin with a flat side, if there's no flat side try a different supplier, you don't file them unless reapplying
(someone mentioned magnetic, I always thought they were led)

FBinNY 

Referring to the sketch in post No.5 (above) makes it easier to understand.

auchencrow

A picture tells a thousand words!
@FBinNY - I am a Bikesmith Cotter Press advocate - but not because using a hammer (with adequate crank arm support) is not effective: You are, (as usual) 100% right-on about the efficacy of using a hammer, and you are certainly one of the most knowledgeable guys on this forum, so I would not presume to contradict you, but the real reason why I no longer use one (a hammer) is because I'm a little eye-hand uncoordinated when it comes to swinging a claw hammer in close proximity to a valuable, or virtually irreplaceable, 70 year old chain ring.

More people than are willing to admit would be far better served by using a cotter press for that said-same reason.

FBinNY 

Probably true, and the tool might make sense for someone working on cotters on a regular basis. BITD many shops used the Var monster shown here even though it wasn't cheap.

There's nothing ever wrong with having and using tools made for the job, but I'm a believer in skill building, not tool shopping, so I post about how to do jobs with tools at hand.

Keep in mind than many who post here might not have $66.00 to spend on a tool they'd rarely use. If they did they might not be dealing with cotters in the first place. So I'm not saying don't buy the press, just that you don' have too.

BTW- those who can't drive a nail without bending it can hammer cotters using a drift punch, and if they're nervous about hammering their hand, can hold the punch with a pair of vise-grips.

Grand Bois

Mostly good advice here, but the point is not to change the angle of the cotters as one poster suggested..

rhm

This comes up every time we discuss the subject of cotters. Someone recommends the hammer. Someone else recommend the BikeSmith tool. Someone else reluctantly points out the shortcomings of the BikeSmith tool. That last one is usually me.
Look, the BikeSmith tool is great for the cotters on your garden variety three speed, especially one with a chain guard. But the finer cranks that came on lightweight bikes, with no chain guard, are both thinner and more delicate. I have two Williams cranks, and one marked Constrictor, on which the cotter is too close to the spider to fit the Bikesmith till. On these I use the modified Harbor Freight chain breaker, or a vise. These are cheap tools ($10-$15 depending on what's on sale) and are both easier and safer to use than a hammer.

I know many people have good luck with the Bike Smith tool. I'm not disagreeing with them. But many others do not.

mparker326

Thanks for the good advice.

It was mentioned on here that filing should be the exception. I never had to file until I came across a Peugeot cottered crank. Original cotters were the "Peugeot" cut as mentioned on the Bikesmith site.

My LBS only had half cut French cotters. So I figured I would try my hand at filing. It was a terrible experience and I ended up converting it to a three piece crank. I acquired another bike with a unique BB that requires only a single cotter so conversion is not an option.

FBinNY 

I avoid filing by replacing with matched pairs of cotters, but this doesn't seem to be an option for you.

Clamping in a vise and filing flush to the tops of the jaws assures a flat wedge area.

Your problem won't be filing, it'll be determining and duplicating the angle you need. You might do this trial and error, by estimating the angle, and filing it steeper (short wedge area) then testing the angle. Then you can make it longer and shallower by degrees until the angle is right, and finally using a guide or the magnet-and-shim technique to clamp it higher and file the same angle to the right depth.

FWIW- the depth isn't critical as long as it's within the range that allows the nut to thread on properly, yet not so deep that you run out of thread.

Reynolds 

OP, surely you knew this already, but remember the cotters must be inserted opposite each other, otherwise your crankarms won't be at 180.

mparker326

I have made that mistake before, but this wasn't the case on the Pug.

I hope to get my one pin out without destroying it so I can just reuse.

@FBinNY, I did find it funny that in the VAR catalog scan you posted, that a hammer was also available as a second option.

Salubrious

Re the hammer thing: a brass drift or one made of hardwood is recommended, especially if its your first go and you don't expect to get a press. The problem will be that of smashing the threads on the cotter pin, rendering it scrap. A Brass drift is usually a bit softer which helps in preventing damage to the threads.

Blocking the crank arm is also essential- there are often a nice set of bearings, BB axle and bearing cups that don't deserve the damage a hammer blow can bring. Block the arm in such a way that the finish of the arm is intact once the blow has been administered!

For this reason, if in a pinch, I would try a 6" C-clamp and a nut from a large bolt such that you fit the nut over the head of the cotter pin to provide space for it to move while applying pressure to the threaded end with the C-clamp in the same way as a cotter press (which is essentially a specialized C-clamp anyway). You might want to use a large crescent wrench to convince the threads of the C-clamp to turn.

Quite often corrosion is an issue- if this is the case and efforts with a C-clamp have led no-where, a shot from can of Kroil (Penetrating-Lubricating Oils) can be really helpful. The stuff stinks IMO, so I prefer to use it outside, but its about 1000x more effective than WD-40 and about 100x more effective than Liquid Wrench. You do have to give it time to creep into the area you want to loosen though. In a cotter pin, perhaps about 3 minutes. Since there is some possibility that the cotter pins were filed (and so have been rusting) upon initial installation, Kroil can really save the day. A small amount of heat can be judiciously applied- keeping in mind that a vintage paint finish is only inches away.

FWIW dept: a very respected mechanic in this neck of the woods (St. Paul) is Steve Hamel, and I am sure some of you on this forum know who he is (even though he is more likely to be working on a 1937 Miller race car or a '47 Vincent). Kroil is a thing that is never missing in his shop.

FBinNY 

Even if you can't reuse it, you want to preserve the angle, so it's easier to duplicate with less trial and error.

Use the Vise method, putting something with a hole over the head end, and use the vise to press the threaded end into the recess you provided. You can also get them out intact with a hammer, but it's iffier if you're not spot on using this method.

Reynolds 

If you remove the wheels and get a helper, a bench vise + 1/2" nut can be used as an extractor.

jwarner

Another for the hammer crowd (I will go so far as to say I use an old carpenter's claw hammer for this purpose due to the rounded face on the hammer head). If all else fails, big brass drift punch and dead blow hammer. Granted, this all depends on comfort level, and the safe bet is likely the press. The C-clamp method described ^^^ also seems like a perfectly valid way to go.