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Maybe this is topic for English board, but it's terminus technicus

I'm seeking a name for the shape which secures two parts in a defined mutual position. The literal translation from my language is "lock".

For example: I want to make two shafts concentric, so I make ??? on their ends. On the first shaft, I reduce its outer diameter from 100 mm to 80 mm for last 10 mm of its length. On the second shaft, I made the negative shape. So these parts fit in.

Result of previous paragraph

What word can replace ???

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    $\begingroup$ "Mating connector" ? $\endgroup$ Apr 27 '17 at 14:52
  • $\begingroup$ Mating connection sounds good. $\endgroup$
    – Lluser
    Apr 28 '17 at 11:05
  • $\begingroup$ There is a high chance there is no english word for this. $\endgroup$
    – joojaa
    Apr 28 '17 at 13:27
  • $\begingroup$ The male side would technically be a "boss", but the female side could have many names, such as "center-drill", "recess", "socket". $\endgroup$
    – user6335
    Sep 26 '17 at 7:20
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One specific form of such shapings is a "taper" - such as the well known Morse tapers.

I don't know of a term for the general feature you're looking for, but tapers are adopted for many instances of it, probably because of their self-aligning nature. Consider the consequence of a machining error in the ID or OD of your diagram above - it will result in either imprecise alignment or no fit at all.

A similar error on a taper would translate to perfect centring with a slight displacement in the axial direction.

Morse tapers for example not only provide centring but can also provide drive force. Morse tapers are self-locking due to their shallow angle, combined with material properties such as friction and elasticity.

There are other tapers which are self-releasing (I believe the R8 tapers used in industrial tooling would come into this category) - they require some other means to hold the parts together - often a collet closer.

Indeed, many systems of collets use tapers to guarantee high accuracy in centring (low runout).

Fitting a backplate to a lathe chuck is precisely this operation without a taper, and I see this instruction page uses the term "spigot" for the male part, but the female part (in the rear of the chuck) is simply called a "recess".

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  • $\begingroup$ Thank for your answer. Unfortunately this is not word what I'm looking for. I'm looking for a name for whole measurements group, which secure parts mutual position. In this group is tapper, as well as spline. Maybe English doesn't have a word for this. $\endgroup$
    – Lluser
    Apr 28 '17 at 10:56
  • $\begingroup$ See edit for one alternative. $\endgroup$ Apr 28 '17 at 11:03
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I can't think of a good name for the "complete concept" here (and this doesn't seem to be a complete drawing of the structure anyway).

There are several names for parts of this type of joint, for example boss, bush, fixture, flange, lug, pad, shoulder, etc. This http://homepages.cae.wisc.edu/~me349/resources/engineering_terms.pdf might help you choose the best term.

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  • $\begingroup$ male / female springs to mind from the picture... $\endgroup$
    – Solar Mike
    Apr 27 '17 at 15:00
  • $\begingroup$ Thank you, I'm not looking for complete concept name. It is only name for some shape which removes some degrees of freedom. Nevertheless, big thanks for Engineering terms! $\endgroup$
    – Lluser
    Apr 28 '17 at 8:39
  • $\begingroup$ Coupling, mating, connecting, suiting, engaging,interference fit joints. $\endgroup$
    – Narasimham
    Apr 28 '17 at 20:29
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I'm not sure if this is the term you're really trying to describe, but my first thought was a spline.

I have a couple issues suggesting that though, mainly:

  • It is for a rotating shaft (this is not specified in your question, and AFAIK it's only a spline if it transmits rotation)
  • I believe splines are specifically on the mating concentric edges, where as your picture seems to suggest it is the mating parallel edges that are transmitting the motion (again assuming these shafts rotate)

If the shafts rotate and it's the parallel edges that mate, coupling might be a better term.

If they are not rotating this answer should be disregarded and you can sort through the terms in the other answer.

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  • $\begingroup$ Thanks. Maybe I'm looking for word which is not exist in EN. It is used generaly for some shaped surfaces which remove some degrees of freedom between parts. Shape doing this too, but this term is too specific. I think, my example can be described as shouleder (shaft) end. And the counterpart is rim ended. So when I want to describe tolerance there, I can write: Tolerance in shoulder/rim connection... What do you think? $\endgroup$
    – Lluser
    Apr 28 '17 at 8:35
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I've always known this to be classed as a 'locating pin' or simply 'location' or even 'mating'. It also depends on the type of fit you are trying to achieve, whether it is an interferance, clearance or transition fit.

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What you seem to be describing is commonly called a keyway (and the male portion is called the key).

On rotating shafts with significant torque transmission you can use a spline. A keyway isn't always like your illustration, but it is common in tooling/machining to ensure alignment.

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  • $\begingroup$ This is incorrect - he's describing a feature to ensure concentricity, not a rotationally rigid connection $\endgroup$ Feb 23 '18 at 13:20
  • $\begingroup$ Thanks for reply, but key is there for torque transmission. My shape is for (precise) centering only. Basicaly, it's not neccesary for proper function, but helps during assembly. (You are not obligated to use pins or semething like this.) $\endgroup$
    – Lluser
    Feb 27 '18 at 9:17

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