Vocabulary: Collet or Cotter 3

[ivymike]

Hello,

I'm in the middle of a discussion at work about whether a particular component should be called a collet or a cotter. I'm of the opinion that if the other parties involved feel strongly about the name, they can call it whatever they darn well please, but I still think that there is a proper name for this particular component.

Does anyone have good "engineering" definitions of collets and cotters that would highlight differences between the two?

My own experience has been that collets are single pieces of material that wrap all the way around something and clamp it in place, while cotters are wedge-like devices that are usually combined in groups to hold something in place. (The biggest difference being collet = 1 pc, cotter = 2 or more pieces)

 

[MintJulep]

From Dictionary.com

col·let
n.
A cone-shaped sleeve used for holding circular or rodlike pieces in a lathe or other machine.
A metal collar used in watchmaking to join one end of a balance spring to the balance staff.
A circular flange or rim, as in a ring, into which a gem is set.

cot·ter
n.
A bolt, wedge, key, or pin inserted through a slot in order to hold parts together.
A cotter pin.

Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

 

[clun]

Collet-
A split, coned sleeve to hold small, circular tools or work in the nose of a lathe or other type of machine

Cotter-
A tapered piece that can be driven in a tapered hole to hold together an assy of machined or structureal parts.

 

[Kapitan]

Just think of it in simple terms :- Collet as Female, Cotter as Male.

 

[drgauf]

Collet is a manufacturing tool

cotter is a manufacturing component

 

[ivymike]

Collet is a manufacturing tool
cotter is a manufacturing component

Um... they're both machine components. Collets are used in many applications that couldn't be considered "manufacturing tools." One example would be the eraser holder on certain pencils.

Collet as Female, Cotter as Male.
Aren't many collets simultaneously male & female (they go into a hole and have a receiving hole as well)?

In the case of a valve cotter, which holds a valve spring retainer to the top of a valve, the parts look and act a whole lot like a collet. The valve spring retainer has a conical recess with a hole at each end. The valve tip passes through both holes, and has a circumferential groove near its end. The valve cotters are a couple of conic sections, each with a lip at the top. The lip interfaces with the groove on the valve top, and the retainer smooshes the cotters up against the valve. As long as the retainer has an axial force acting on it, there will be a substantial radial force to hold the valve in place. The cotters are, in this case, basically a collet that has been split into two pieces for easy installation. This is the particular situation that sparked the discussion initially - one person wanted a pair of "valve collets" and the other wanted a pair of "valve cotters." I happen to think that the second person was correct.

 

[EnglishMuffin]

There are some chucks which have physically separate segmented jaws similar to the retainers on valves described by InHiding, which are commonly referred to as collet chucks. I have never heard them referred to as cotter chucks. And I have frequently heard people refer to conical valve retainers as collets, but never as cotters. I have a feeling that common engineering parlance is to refer to multi-part or one piece multi-segmented frustro-conical devices as collets. And ultimately, it's what most people call things at any given moment in time that appears in contemporary dictionaries, even though it often originates from ignorance and careless usage. However, there appears to be little doubt that single tapered retaining pieces are often referred to as cotters, such as the cotter pin commonly found on bicycle cranks.

 

[ivymike]

I have frequently heard people refer to conical valve retainers as collets, but never as cotters.

Here are some examples of catalogues referring to these parts as cotters:

http://dratv.com/valcotsoleac.html

http://www.minimania.com/web/CatPage/2-31/Chapter/2/Page/31/MiniCooperCatalog.cfm

Here are some examples of people calling the same parts collets:

http://www.mbpducati.com/4v/colletoverview.htm

http://www.2wf.com/articles/bike_tests/6CAB6F3A-7BB9-4B50-9364-B3B36ADDA072.asp

I guess that there really isn't a "correct" term in this case.

 

[EnglishMuffin]

InHiding: Don't get me wrong - I suspect that you are technically and historically correct. But virtually every word we use once meant something slightly different. I rather like these "definition" questions, of which there are dozens on Eng-Tips, but ultimately they always seem to end inconclusively. The meaning of words keeps changing and the popular vote wins.

 

[murgle]

>Collet as Female, Cotter as Male.
>Aren't many collets simultaneously male & female (they go into a hole and have a receiving hole as well)?

 

[ElwoodGreen]

This is too hilarious.

My Websters Vest Pocket says (if I read the abbreviations correctly) that is is the present tense of be.

By the way, if any of you ask a shop tecnician, he will tell you those components are neither collets, nor cotters, because everyone calls them valve "keepers" (at least in the western US).

 

[MouseTrap]

Come on guys......

Never heard of a 'Whatchya-ma-collet'?????

Everyone knows what that is!

 

[EnglishMuffin]

kpuddarby:
Now your talkin! I think the use of the word "keeper" is most apt and fits in well with the fine American tradition of discarding or bringing up to date obscure Old English words that nobody uses much any more and whose original meaning has long been forgotten. And why, if a cotter is supposed to be a single tapered component, as some have suggested, is it commonly used to describe wire-formed split pins, in addition to the tapered pins found in bicycle cranks? And what on earth is the descriptive value of a term like "cotter" if it can be used to descibe simultaneously "A bolt, wedge, key, or pin" as MintJulep says?

 

[chicopee]

This forum is too hillarious!!

 

[ietech]

Chicopee
Another entertaining thread is ( thread406-75530 )--- Pulley vs. Sheave definition please --- in the " Gear and Pulley Eng. Forum"