A general fact, I once had in excess of 500 ft-lbs on a Craftsman 1/2"
breaker bar and 19mm 6 pt socket.  Broke it.  It was a shitty new craftsman
socket.  This was on a '73 parts van that had sat for 6-8 years, I had a
half assed idea of keeping the calipers.  I define 500 ft-lbs as a 225 lb
static load (me) on a 18 inch breaker with about a foot extension.  I
proceeded to take my 19mm Harbor Freight 3/4" drive T bar, and easily a  5
foot lever arm, and again my full static weight, plus impact (me jumping)
before the thing broke, that has got to be 1100+ ft-lbs, and amazingly every
nut came off, no broken studs.  3/4" is simply a difference in class.  HF
stuff is cheap crap as a rule, but the 3/4" stuff is so heavy, I'll bet no
one can realistically break it doing anything normal or even slightly
abnormal to a van.  Everyone should buy a set immediately.  I'll note they
supply the set variously in 6 or 12 pt depending on whim, and when it is
bought.  I'd opt for 6 for strength (check the other importers, Enco, etc)
but 12 for ease of use.  The driver is sort of crap but the T bar,
extensions, and sockets are as heavy as craftsman, just not as well
finished.  A caveat, I don't think the HF set contains the 19mm any more,
mine did, later set of a friends does not.

On the origional question, 3/4" is 19.05mm and .05mm is a sheet of paper, so
if you want an indestructable 1/2" drive tool, simply buy a 6 pt Snap-On
3/4" socket, it will outlast you.

John
vwbus@mindspring.com