For the second time this year, I found several of these small cotter pins in a bicycle clean out, this one was an old shop that had closed down years ago, the guy ran it out of his basement. Much like another shop I cleaned out about four months ago these were in a small drawer along with a bunch of tapered pins. The pins go from about 5mm down to about 3mm. The cotter pins are short, about 1/3 the size of a normal crank cotter pin. They are 8mm in diameter and the threads are 5mm. The barrel part is about 14mm long. The cotter and nuts are steel, each one is used and slightly bent from removal.
The first time I found these I figured maybe it was some oddball older bike that used something like this for a seat post or something but someone else said maybe they're off a kids bike or tricycle of some sort?
The long pins are very hard steel, I can't scratch them with a hacksaw blade. Each one though appears turned on a lathe and parted with a cutting tool.
My first thought was that these were pins often used to repair casting cracks by a machinist but now that I again found these among bicycle parts, I figured I'd ask here. They are too hard and brittle to use as a punch or drift, they chip and break like a hard drill bit. At both places the both the pins and cotter pins were in the same drawer. The assortment of parts from both places ranged from the early 1900's to the early 70's.

Your hardened pins look like a partial set of well worn shop made transfer punches, generally a really fine point indicates that the punches were used for sheet metal. Shop made fransfer punches are generally made from drill blanks.
The punches follow drill bit sizes exactly and are available in fractional, number, or letter sizes. Somewhere in the world I'm sure someone make a metric set.



: Mike

The long pins are tapered, the tip is spiral cut, as if it was cut and sheered off. All are similar but not identical in length as if each one was cut by hand on a lathe without measuring. Not all have the nib on the end, many are cut smooth. A transfer punch is straight sided for alignment reasons.
I would also think they'd be longer if they were punches, at just under 4" long, they're a bit short for a punch type tool.

Both places had a bin full of these, with the small cotters mixed in. They're extremely hard, so much so they chip or shatter when hit.

darn, thought we had found a vintage thingamabob. rare.

Someone might have been experimenting with turning their own cotters?

-Kurt

^^^^ I would not choose high carbon brittle steel for cotter pins. They sure look like a tool of some sort vs functional bike part.

I agree, but consider where they were kept. Someone might have DIY hardened them too.

Come to think of it, these might be drill bit blanks.

-Kurt

I found a set of those "drill blanks" at a garage sale some years ago. Coincidentally, just last week I finally used them for something, pushing the hollow locking pin out of the drive gear on my old Isuzu's distributor. Amazing how sticky that an old distributor's vacuum and centrifugal advance mechanisms can get after 32 years, steel-on-steel mechanism with zero remaining lubrication in evidence.

I thought about drill blanks but what about the taper? They're too hard to turn the way they are, so they had to be hardened after the machine process.
I wouldn't have given these a second thought if I hadn't found nearly identical drawers of them at two different old shops, hundreds of miles apart.
The fact that both were mixed with the oddly tiny cotter pins also got me thinking.
The cotter pins are too small to be for cranks, at least not on any adult bike, they're less than half size, plus the threaded portion is super long. I'm thinking they must have been for some odd ball seat clamp set up. Also the fact that the majority of all the parts from both shops were pre-war, it really made me wonder what they were for.
I was sort of thinking these were some sort of locking pin for something, or a wedge of sorts. Both guys had dozens of them in a drawer, combined with the same tiny cotter pins, and both drawers contained several of these pins that were broken or cut short, as if the tip had been hammered in and snapped off.

Those are likely antique tricycle parts. Back in the day many tricycles with forged cranks that connected to the front axle or wheel were secured via a wedge pin or small cotter like that. I'm talking 20's and 30's or maybe even earlier. In order to remove the crank, one or both ends would have a wedge pin hammered in place and peined over on top. They would be removed either with a long punch or another pin. from the opposite side. I also seem to remember similar pins holding the right crank arm to the crank axle on early boneshaker models, forming sort of what resembled a Thompson BB set up but with the left crank arm being threaded in place with a captive nut that was either pinned or held in place via a set screw.

I'd pay close attention to a lot of parts containing older bits like that, you never know what you may find. Those old shops like that are getting fewer and fewer these days, if there's any even still left at all.

The use of pins to secure things to shafts is still used in some machinery, https://www.grainger.com/category/fa...ns/taper-pins#

I think this may be it, there's a few boxes of really old cranks, some have the crank axle attached to the right side and there's threads on the left end of the crank axle.
A good bit of this lot is pretty early, I've never found a whole box of old Corbin and ND model A hubs before. None in rims, just old hubs. Both these places were guys who were in their 90's when they passed over 45 years ago, so chances are they dealt with some of this stuff when it was still current or at least 'recent history' to them.