On Thursday, June 18, 2020 at 4:09:37 AM UTC-7, maxq wrote:
I'm making a special tool out of a 3/8 drive socket. It'll have to be
turned by a wrench or gripped by vise jaws. I'll file flats on the
square end.

Should the flats be parallel with the square's sides, or have the point
in the middle? This is a high-torque situation.

Long-time lurker, infrequent poster. WAG Could you modify a socket-headed end wrench so the socket head is "just deep enough"? Like others have said, "not enough information". How much past the drive end are you actually looking to file off? IMHO Something you can file and high-torque sound mutually exclusive.
Signed, "former metals shop dropout".