Hi all,

My planes are mostly 40 / 60 size units. For the most part they use 2-56 size rod at the ends. Some call for 4-40 size rod for the ailerons. I use standard sized servos with torque ranging from 45 - 90 from Hitec & JR. Servo horns are standard nylon stuff provided with by the mfg. Control surface horns are nylon pieces from Du-bro, Great Planes or SIG.

It appears that the horn holes are 1/16" - at least my pin vise with a 1/16" bit is snug but doesn't remove any material. When I snap a standard 2-56 clevis on the fit is very snug. If I chose to open the horn hole up with a 5/64" bit the fit is sloppy - there is noticeable slop at the control surface - especially when both the servo horn hole and the control horn hole is opened up to 5/64".

What is the proper technique for correctly sizing the holes in the horn (servo or control surface) and a clevis (threaded or soldered)?

What size bit should be used to open up the horns when using 4-40?

TIA,