5.5x2.0mm barrel power connectors are not all the same size

[mcovington]

Curiosity of the day: 5.5-mm barrel connectors are not all the same size.  American-made ones apparently run slightly larger than 5.5 mm, and Asian ones run slightly smaller.  I encountered a Chinese-made piece of astronomy equipment that would not take an American 5.5x2.0 plug but would take an Asian one.  More here:

https://www.cloudynights.com/topic/715177-why-some-55x20mm-power-plugs-dont-fit-ioptron-mounts/?p=10301786

[SilverSolder]

Curiosity of the day: 5.5-mm barrel connectors are not all the same size.  American-made ones apparently run slightly larger than 5.5 mm, and Asian ones run slightly smaller.  I encountered a Chinese-made piece of astronomy equipment that would not take an American 5.5x2.0 plug but would take an Asian one.  More here:

https://www.cloudynights.com/topic/715177-why-some-55x20mm-power-plugs-dont-fit-ioptron-mounts/?p=10301786

Some people just don't have any standards!

[Gyro]

True, the nearest 1/64 inch will do. 

[mcovington]

I think the point Switchcraft missed is that this is a part that is supposed to fit into a hole, and the hole might be made by a different manufacturer.  So its specified diameter should be treated as a maximum, not plus-or-minus.

[Rick Law]

The length also seem to have two typical ones - longer barrel (deeper socket) vs shorter.

 I have two sets, one a few months after the other.  They ended up being different length sets: one has a longer barrel paired with deeper sockets, another has shorter barrel and less deep socket to match.

The longer barrel ones can fit into the short barrel socket just fine but with more back-end sticking out even when fully inserted.  The other way (using short barrel with longer barrel deeper sockets) appear to work less well.  Just extra work, now I have to manage them as two different parts-set when I make things; instead of just picking out a male or female, I have to make sure I try it out first to ensure matching with the other end already picked/installed.

[TimFox]

For mating parts, they both should be specified as "maximum or minimum material":  see https://www.emachineshop.com/maximum-material-condition/
This is more foolproof than "+/-" tolerance on dimensions.

[mcovington]

Of course.  The size of the barrel is a maximum; the size of the hole is a minimum.  (Both are maximum material conditions; that is, both say the maximum amount of metal you can leave behind.)  Simply specifying them as the same number, plus or minus variation, will guarantee that sometimes they don't fit!

[MarkMLl]

The length also seem to have two typical ones - longer barrel (deeper socket) vs shorter.

This was mentioned elsewhere recently in the context of the TS100 soldering iron, which apparently requires a ~15mm connector when the de-facto standard is 1/2".

https://hackaday.com/2020/07/09/the-simplest-ts100-upgrade-leads-down-a-cable-testing-rabbit-hole/

Apropos the "Americans tend to larger, Asians tend to smaller", I think one has to consider /which/ of the Asian countries. As specific examples, Japan, South Korea and the Philippines have a tradition of manufacturing for America so could be expected to inherit America's idea of the Metric System, while China was at least in part influenced by the USSR which had a- how shall I put it- rather more rigorous approach.

MarkMLl