Re: [CR]cottered cranks question

Example: Racing:Wayne Stetina

Date: Fri, 09 Feb 2001 09:39:41 -0500
To: "John Swarbrick" <>,,
From: Harvey M Sachs <>
Subject: Re: [CR]cottered cranks question
In-Reply-To: <>

Let's think about cotter pins, hammers, and tools for a minute or two. I have not doubt that Mr. Reid can get a good fit with a file (I do ok starting with a grinding wheel) for his cotters. I lack confidence that this will hold, and still require a robust method to remove the cotter. I recently acquired a VAR adjustable cam-over tool for this job, which is sort of equivalent to triple-sized vise-grips. Before that, I used a jig which was very helpful.

To me, the key is to avoid hammering on a cotter when the crank is not supported. If you do that, the impact blows are transferred through the spindle to the ball bearings to the cups, increasing the likelihood of pitting problems (I believe, w/o metallurical knowledge). So, I built a stand that sits on the floor. The "business end" is a vertical 2 x 2 board, with a shallow hole in the top to clear the end of the cotter or its nut. The top of the 2 x 2 is rounded a bit, and clamped with a radiator clamp to prevent splitting. to use it to remove a cotter, I loosen the nut till the nut is fllush with the end of the cotter threads, and have my trusty, lovely, assistant hold the bike over the stand, so the crank rests on the top of the vertical 2 x 2, with the butt end sticking down. Then, I hit the cotter with the hammer. It loosens the pin, while the stand holds the crank arm and keeps the impact from the bb bearings. An ASCII sketch:

|o o| crank | | | | | | | | |______________| base

Oh, well, my background is not in art. Add hammer and stir. Keep thumb out of the way.


At 13:59 2/9/2001 +0000, John Swarbrick wrote:
>Hi Bob,
>I have a cottered crank fitting session coming up soon.
>I'm using Durax cranks with a Baylis Whiley BB with english cotters
>My problem is that when I 'dry fit' the axle and cranks together. The
>cotter pin goes through the 'correct' ammount on the spider side and only
>needs a bit of filing for a perfect fit. However on the LH crank
>the pin barely goes through at all, with only a bit of the thread showing
>at the end. This is going to take lots more filing. I guess the more you
>file the more chance you have of altering the angle of the 'flat' and
>therefore the cranks won't be 180' apart.
>Is this normal or do I need to get some other cotter pins.
>swaping the pins I have around makes no differance. I'm guessing the
>differance lies in the BB axle or crank.
>Your right you can 'feel' quite accurately with a spanner.
>>From: Bob Reid <>
>>To: <>
>>Subject: Re: [CR]cottered cranks question
>>Date: Fri, 09 Feb 2001 13:08:18 +0000
>>If you get the 'fit' right first the amount of "drawing-on" you have to do
>>shouldn't mean running the risk of stripping the threads. I say shouldn't -
>>but this of course is dependant on just how hard and what's used to tighten
>>the nut. I got taught at college, that torque wrenches were just a more
>>accurate spanner - spanners then being uniformly of a length that the
>>"average" man would tighten it properly and yet not exceed the elastic limit
>>of the bolt/nut combination when applied correctly (i.e. no bars or tubes
>>involved), but this was for "standard" bolts where they were designed for a
>>specific clamping load tightened by "standard" spanners - and then there
>>were cotter pins, cycle threads and tools (engineering on a budget) and a
>>virtual thread war between B.S.A. and Raleigh.
>>When your faced with a cheap cotterless crank wedged onto the BB axle and
>>with no threads left for the extractor to grip on - you might just remember
>>how easy most cotter pins were to come out if done correctly.
>>p.s. I still have not came across "standard-man" (though we do have case law
>>who says who he is - the man on the Clapham Omnibus)
>>best regards
>>Bob Reid
>> > From:
>> > Date: Fri, 9 Feb 2001 06:58:25 EST
>> > To:,
>> > Subject: Re: [CR]cottered cranks question
>> >
>> > I don't see anything wrong with fine tuning the fit with a file, on
>> the other
>> > hand I thought you weren't supposed to draw the pin tight with the nut
>> > because of danger of stripping the threads on the pin and/or nut.
>> >
>> >
>> > Pete Geurds
>> > Douglassville, Pa