we use g90g43h# in all of our paths along with the m6t# .
G43 is tool length offset, and uses the tool length to offset the tool.
I do understand lengths as well as the fidia I have a laser and it picks the length off all the cutters sorta like I would have to do in mach 3
So the laser is measuring the tool length.
I'm pretty sure you're using the length at work, and you just don't realize it. Unless you touch off every tool before you use it, the lengths have to be stored. If you use an ATC without the control knowing the tool lentgh, then you're using an ATC like a manual tool change.
In Mach3, if you zero the tool each time you change it, then Mach3 doesn't need to know the length, UNLESS you use a G43 length offset.
Mach3 also doesn't need to know the diameter, unless you're using G41/G42 comp.
And Mach3 has no idea, and doesn't care what kind of tool it is.