American 3 pin mains plug and socket

[N_Cook]

The third grounding pin seems to be always round and with no taper in any
sense. The socket I have here has a ground-pin recess that is a conflation
of a semicircle and half a square in cross section . Equally solid, ie no
springing action. Or is there a taper down the length of the ground pin
recess that I cannot gauge . I expected a round pin with a tapered flat and
a slot along the length of the pin to give some sprung gripping/ latitude
for dimensional inconsistency.

While at it, are the holes in each flat pin , for anti-tugging latch pins ?

 

[Jeffrey Angus]

While at it, are the holes in each flat pin , for anti-tugging latch pins ?

That's to make it easier to connect solid wire from the outlet box
directly to the plugs when you're too cheap to buy a new receptacle.

Jeff

 

[N_Cook]

IIRC,a new receptacle costs less than $1 at Wal-Mart.

BTW,I've seen a lot of US power plugs with ground pins that are folded
sheet brass that has the half-round/half-square,or U-shape cross-
section,with a bevel at the end. Maybe cheaper to make than a solid round
pin?

the holes in the flat blades are probably a leftover originally intended
for some sort of detent (ball detent?)to help retain the plug.

--
Jim Yanik
jyanik
at
localnet
dot com

I should have said I am in the UK
Now you say that I've seen a plug with a U channel ground pin ,somewhere
along the way. I could see that arrangement maybe giving some sort of
sprung/ tolerating fit. But how does a cylindrical brass pin make good
contact with an unsprung receptacle pin ?

 

[Allodoxaphobia]

As for the holes in the flat pins, I can't find a reference easily but
believe that they are for dimples in earlier sockets that are no longer
present. It could also be that dimples exist in ceiling outlets
only...you can do some hunting and report back!

I have seen, in the past, 'security' locks (both metal and plastic) that
engage both the mains pins through these holes and prevent insertion
into an outlet.

Probably NOT what the holes are for, but such a lock could be A Good
Idea on some appliances or equipment in an environment with children.

Jonesy

 

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While at it, are the holes in each flat pin , for anti-tugging latch pins ?

Close - spring loaded pins with a ball-shaped end, designed to hold
the blade in the outlet. As better alloys were developed the
construction became much simpler, but the detents remained.

PlainBill

 

[N_Cook]

I came across an old bakellite 3 pin USA receptacle yesterday. The third pin
socket in that was 2 definite sprung flat contacts, touching across a
diameter of the pin