2-56 Control rod question
 

I purchased several 2-56 size control rods to set up the control throws on an airplane. I also bought a 2-56 die to thread 2-56 rods to make the aeliron control rods with. Using the die without a handle, I was able to cut the thread on one of the 2-56 rods. Then I tried to screw a 2-56 clevis onto the newly threaded rod only to discover that the clevis just slid on the rod without screwing on. What am I missing? What size of rod should I use to cut a 2-56 thread? What is the real size of a 2-56 clevis? What is the real size of the rod?

RE: 2-56 Control rod question
 

The threads are rolled on a wire which makes the thead larger in diameter than the rod. I have threaded 3/32 welding rod using cutting oil because it's a tough fit. I grind the rod to a taper to help starting the tap then put the tap in a vice and use a variable speed drill to turn the rod. Good luck.

RE: 2-56 Control rod question
 

You are sure you got 2-56 clevis and not 4-40? They look pretty much the same but the 4-40's are a bit larger and stronger.

Why did you get blank rods when threaded rods are so easily available? You would only put a threaded clevis on one end anyway, and it would not thread all the way down. You would use the clevis on the aileron horn and then make a 90 degree bend on the other end and use a keeper on the servo arm.

So, I am not sure why you would want to thread your own rods.

RE: 2-56 Control rod question
 

What Scratchonly said. The clevis is designed to go on a 2-56 pushrod that has had the threads rolled into in, not cut by a die.

Ken

RE: 2-56 Control rod question
 

Now I didn't know that. Learn something new every day. I just thought they were cut and that was that.

Well, that certainly answers why chasing a thread with a die to clean it up seems to end up with loose threads on the back-up nuts. I guess I should just take my own advice and just buy replacements instead of trying to salvage damaged ones.

RE: 2-56 Control rod question
 

>>You are sure you got 2-56 clevis and not 4-40? They look pretty much the same but the 4-40's are a bit larger and stronger.
Yeah, I pretty sure. At least the package was marked 2-56 that I got the clevis' from.
>>Why did you get blank rods when threaded rods are so easily available?
The rods that I bought were threaded on one end. It was my intentions to use one rod to make several smaller control rods. I use a z-bend for the servo arm on ailrons and wanted to cut threads on the other end of the rod.

RE: 2-56 Control rod question
 

Thanks, sounds like a good idea to me. I'll try it.

RE: 2-56 Control rod question
 

http://www.portlandbolt.com/faqs/rol...ead-bolts.html

This may explain rolled vs cut threads.

RE: 2-56 Control rod question
 

This chart gives the dimensions of assorted threads..

Note that the 2-56 thread has a max diameter of .0854

If you want to cut your own threads your rods must be that size or slightly larger..

I've checked some of my rolled 2-56 rods and most are less than .08

The rodchuck folks recomend 3/32 welding rods for cutting 2-56..
http://www.rodchuck.com/

Don't use music wire.. it's to hard.. Trust me.. I ruined a 4-40 die trying.

Get Welding Rod.. You can get it in Stainless or mild steel.. the Rodchuck site has a good guide.

RE: 2-56 Control rod question
 

The only issue with threading the welding rod, is tht you can leave the rod workharden and brittle at the end of the threads. A sharp die, and lots of threading oil and 3/4 on 1/4 off when threading (breaking the chips) will reduce this problem. The other diown side is weight. My suggestion is to solder a threaded adaptor end on the unthreaded end of the wire. Works every time.

Don

RE: 2-56 Control rod question
 

The 2-56 size thread is part of a family of threads known as "machine screws". There is an interesting formula for calculating the correct rod diameter for a machine screw. It is (Thread # X 13 + 60)/1000. The thread number for a 2-56 thread is 2. The rod diameter using the formula is .086 inches.

RE: 2-56 Control rod question
 

Like I said, I will buy the rods and go with that :D

RE: 2-56 Control rod question
 

Save the non-threaded scraps for applications where you don't need threads. These could include the servo ends of wooden pushrods, throttle control rods where one end has a z bend and the other uses an ez connector, etc.

RE: 2-56 Control rod question
 

This is very interesting information.

RE: 2-56 Control rod question
 

"cutting" a thread leaves "stress risers or failure points in the metal. A rolled thread is smoother and less stressfull on the metal especially on brittle materials.

When you run a die over a previously rolled thread you remove material and change what is called the "class of fit". This explains the loose condition.

http://www.natool.com/engdata/data10.php

RE: 2-56 Control rod question
 

I have dealt with making pushrods for my 3d aircraft and have found that rods that are completly threaded are not as rigid as non threaded rods. The threading inside of a pushrod guid can also lead to binding if stray bits of contamination get stuck on the threads. My favorite solution is to cut down a pushrod that is threaded at on end and to solder a clevis on the cut end. It takes a few minutes longer then a z bend or 90 degree bend with a keeper but you do not have to enlarge the servo arm hole and connections have less play and wear better. threads you cut have a tendency to snap if not done absolutely right