3/8" drive dimensions

[Groundhog]

Does anyone have (workable) dimensions or drawings of a female 3/8" drive square hole? (other than Engineer's Edge https://www.engineersedge.com/hardware/square-drive-tools.htm - which I am having trouble understanding). I will probably want to drill the corners before milling so I need to figure what size (and placement) to drill the corner holes.

If I understand Engineer's Edge right it would take a very small drill (to get the proper radius) - like .17x", which means I would have to finish the sides of the hole with a 0.125" end mill. Does that sound right? I'm not sure I have an end mill that size long enough.

I could probably just measure a socket (or weld a cheap socket to my special tool) and go from there but I was trying to dear it up from scratch & got curious - and as always - bull headed.

 

[Tozguy]

After using a 1/8th end mill and breaking it I would say that it is not meant for a very deep side cut, even if it is long enough it is not strong enough. Welding a socket on your tool sounds best to me.

 

[Groundhog]

After using a 1/8th end mill and breaking it I would say that it is not meant for a very deep side cut, even if it is long enough it is not strong enough. Welding a socket on your tool sounds best to me.

That is kinda what I was thinking. I will be breaking drill bits or end mills or both.
So, I think I will either weld (half of) a socket to the tool or mill a 3/4" hexagon on the top that will accept a socket.

But now I'm just curious. How could I make the hole with a mill?

 

[RJSakowski]

A lot depends om the machine operations aqnd the tools used.
My male 3/8" drives measure about .371" with only slight breaks at the corners so I would make the socket .375" with clearance to the corners.
Here is aqn example of how I would cut the pocket with an 1/8" end mill and a 3/32" end mill
I would spot and drill a pilot hole at the four corners of the .3087 square and plunge cut the four 3/32" holes to depth. Then I would drill a 1/4" or 5/16" hole to depth at the center of the pocket and finish by milling to size with an 1/8" end mill.