I am trying to make a threaded pushrod from a 0.093" wire.

I use a 4-40 die and when I finish, the threads on the pushrod does not match the 4-40 clevis, the pushrod just slips in the clevis, like I am trying to conect a 2-56 pushrod to a 4-40 clevis.

Can anybody help me on this ? Is my die damaged or what ???

Thanks.

Obolel,

I would be very leary of threading wire for pushrods. A fellow club member did exactly that and the clevis came off in flight and as a result the plane was destroyed.

We concluded that pre-threaded pushrods were manufactured in such a way that the threaded end was a larger diameter than the rest of the pushrod, and when threaded, the threads were cut deeply into the wire and would hold the clevis.

I don't know this for a fact, but the result sure supports the theory.

My advice to you is to use rods that are pre-threaded.

DaveB

The outside diameter of a 4-40 thread is 0.112. The outside diameter of a 2-56 thread is 0.086. The rod you are using (0.093) is larger than the 2-56 and significantly smaller than the 4-40. The 0.093 just will not allow sufficient material to form a proper thread for the 4-40 size.

For some time now I've been using 7/64" (0.1093) rod for making my own 4-40 rods as required. Granted, this is a difference of just under 0.004 on the diameter, but then cutting the thread is a little easier.

I've never, repeat, never had a 4-40 clevice or nut come loose and I've been using this method for about 10 years.

The threads where the diamater of the unthreaded portion is less than the threaded portion is due to the manufacturing process, which is commonly known to myself as "rolled" threads. This is where the metal is squeezed out of the valley of the threads into the peaks of the threads. The diameter of the unthreade portion will be approximately 0.076 while the diameter of the threaded portion wil be approximately 0.086.

Hope this helps.

I would like to thank both of you for your answers. Messacar, from what you write I understand that making rods in your way is even safer and better than the manufactured ones since your finished rod is a little bit thicker, can we say that ?

I had a similar problem with 2-56 die, only the rod wouldn't even fit in the clevis; there is an adjustment on the die wherein you can make it a little bit larger or smaller for fine tuning.

You can get the tools to make threaded rods for RC at http://www.rodchuck.com/

Messacar has it exactly right, "rolled" threads vs "cut" threads.

Obolel

The difference in diameter will definately affect the strength, but that was not my main consideration. Being able to cut my own threaded rods was the main consideration.

I looked at the site recommended ie: http//www.rodchuck.com/ and that absolutely looks like a very usable product that I'll be taking a further look into.

Regarding the cutting of #2-56 threads, I have been using a 2mm rod and this seems to work very well. The 2mm is .079 and the outside diameter of the #2-56 is .086, a difference of only .007. This also has worked well with never a problem. The metric size rod should be available from any good tool supply shop.

Good luck

Fred

metal working tools ( tap's and die's) are available at a very reasonable price at


ENCO ( http://www.use-enco.com/CGI/INSRHM )

and may other industrial supply dealers. The quality of the tools they sell is super, geared for production.
This may help.