What does the size numbers represent?

2-56 and 4-40 is this english or metric or what?

Thanks

Not sure if figured this out! so a 4-40 means 4 guage wire with 40 threads per inch!

Yep, that's what it means. A "2-56" pushrod is actually a pushrod with ends threaded with 2-56 rods. The actual rod may actually be a different diameter (in fact, the "standard" Dubro 2-56 rods are slightly smaller than "2" in diameter. You can't thread them with a thread cutting die). The funny part is when you have a "2-56" rod and use Z-bends or other non-threaded connectors on each end. So you're seeing a bit of shorthand by referring to the entire pushrod as "2-56" or "4-40", but we all know what we mean, it's a good way to tell how thick the wire end of the pushrod is. (oh, btw, watch out for some ARFs made overseas. They often come with 2mm rods instead of 2-56. Close, but not compatible)

The 2,4,6,8,10,12 numbers refer to the machine screw size diameter. The 56,40,32 ect refers to the number of threads per inch.

The reason you can't cut threads on premade rods is because the manufactures uses rolled threads instead of cut threads. Rolled threads are cheaper to produce.

DEG

Ifly is dead on. First number is machine screw size and last number is threads per inch.

Mark Shuman

Thanks all........great information!
Keep flying!