Vex Shift Rod through 3/8 Hex Shaft?

[asid61]

Originally Posted by KohKohPuffs

My applications for using a shifter rod in a 3/8" hex shaft is for a brake for an arm gearbox. I would prefer to use COTS parts for the sake of machining time and because I know through experience that those work perfectly well without failure (as much). My main concern is if there's a limit to what size hole you can make in a shaft for the shifting rod to go through. Of course, I'm not going to make a hole in a shaft and leave only 0.01" of wall thickness, but I'm wondering if there is a general rule to follow.

In general, hollowing out the center of an axle doesn't cause too many strength issues. IIRC 1/2" thunderhex is 92% as strong as standard 1/2" hex even with the hole through it.
Solidworks Simulation can help you calculate what effect the same torque has on the original 3/8" hex compared to the new one. Or you can plug in equations you find online for the strength of a tube versus a rod in torsion.