Split Cotters

[whateg0]

I have repaired a few machinery pieces that used split cotters, making new parts usually. Somebody on a drill press thread was talking about making new "locking sleeves". When I asked if he was referring to the split cotter that locked the table to the column, he said he wasn't sure, but posted a picture which confirmed that it is.

When did split cotters fall out of favor? Obviously they are a costly option vs. a set screw, but it is my experience that they are excellent at locking a shaft in place. It's interesting that there is so little information about them on the web and very few are familiar with them.

Dave

[pete]

Afaik those split cotters haven't fallen out of favor, at least not yet. Cheaper equipment like off shore drill presses might now split the casting and use a rudimentary threaded shaft and lever instead to tighten the casting against the column. Today I think there mostly used where you don't want any damage done to the shaft or quill being locked. And the higher the machines quality or the older it is the more likely there found.But depending on where and what it is even some of the cheapest off shore machine tools will still use them. One of the Guy Lautard Bedside Reader books goes into a fair amount of detail about how to design and layout your own where ever one might be needed. But it's not that complex if you know enough about how they work. Researching a bit about each materials coefficient of friction and durability helps when deciding what to use. Obviously it's best to use a slightly softer material than the part being locked to prevent marking it. I've always thought they were a well thought out and quite clever system that only requires a properly placed drilled and / or reamed hole, some simple machining and a couple of small parts.

[KellyJones]

OK - I'll bite. What's a split cotter? Do you mean a split "collar"?
Thanks for the clarification.

[pete]

There used on most lathe tail stocks, mill spindles etc to clamp them at a set position. Basically two short sections of rod radiused to fit the shaft or quill being clamped with the lower one threaded. The hole they fit in very slightly bisects the shaft or quill bore. In use the two radiused pieces are squeezed together against the shaft and prevent it from moving. They may have other names depending on your location, but I know them as split cotters.

[jcfx]

Interesting, never knew what they were called, googling got a a lot of hits for cotter PINS.
Thanks Pete, for the explanation !

[Russ Hanscom]

The brits seems to love them for model work. If you want to see a bunch in one place, look at the Quorn grinding machine. Split cotters are actually quite easy to make and very effective.

[liveaboard]

I'm having trouble picturing this; can someone maybe post a picture?

[mklotz]

I'm having trouble picturing this; can someone maybe post a picture?

https://www.youtube.com/watch?v=DdHd0kJ2_3c

The description of the device starts right around 3:00 into the video.

[liveaboard]

Got it now, thanks.

[Lew Hartswick]

They aren't quite as "simple to make" if you cope the ends of cotter to the shaft your clamping. I've done that for the new ones I've made for a Bridgeport quill. I feel that is a better (less marring) thing. It does mean setting up and boring to the right radius.
...lew...