What's the max practical torque for different drive sizes?

[donkmeister]

The "how much torque for my dugga" thread inspired me to go looking at larger duggas again.

I'm on the Hikoki 18+36V systems, and I noticed that the 1/2" big 36V unit is up to 1050Nm, whilst the 3/4" (which appears to be the same body just with a larger drive) is up to 1100Nm. You'd expect the engineers at Hikoki/Metabo have done their sums and decided 1100Nm is just a bit too much for 1/2" but it got me to thinking...

Whilst there are sufficient variables that it's almost impossible to say what is the "max practicable" or "absolute max" torque for a given drive size/system, is there a rule of thumb that 1/8" is suitable up to x Nm, 6mm hex up to y Nm, 1/4" up to z Nm and so on?

I'm not about to rush out to get 3/4" sockets so the 1/2" is going to be the one once I've convinced myself I need 1050Nm, it's just interest.

[Chris32345]

Milwaukee has a 1/2 unit that has something like 1600nm and manages fine