OK - here is what it is looking for control rod retainer for a 4-40 push rod. One end it not threaded.
Brodak shows to sizes.
5/64 and 3/32
So, it is a pushrod we're working on. I'm not clear on what you are piecing together, but here are some things that fit, or can be made to fit.
1. A normal hobby shop pushrod, threaded 4-40 on one end but not the other, mikes a tad over 3/32 where it is not threaded, maybe .096 or .097. 1/8" OD brass tubing .014 wall gives an i. d. of .097, so you can join a bare 3/32 pushrod to a threaded-on-one-end rod with a piece of 1/8 brass, no problem, just solder away. The 3/32 pushrod will be a bit sloppier fit than the threaded-on-one-end rod.
2. The Brodak "3/32" pushrods that come in their ARFs and ARCs are fatter, maybe .102 or .103 or so. Those will
not slip into 1/8 tubing. We don't need much extra room, so slit an inch or so long piece of 1/8 tubing down about halfway, just on one side of the tubing -- not much hassle with a Dremel or a fine tooth metal saw. Slip the fat pushrod into the slit end, and the bare unthreaded part of the 4-40 into the other end. Solder with no worries.
3. Fully threaded 4-40 rod is also fatter than the OD of the bare rod, so a 4-40 thread will not fit into 1/8 tubing. In that case, make a full length slit (if using a Brodak ARF/ARC pushrod). Solder.
4. For a true 3/32 pushrod and a fully threaded rod, slit halfway as in number 2, but slip the 4-40 threads into the slit end. Solder again.
I've done all the above at one time or another, I think. The one I remember best is the one that rolled under the workbench and hid until I made a replacement. If you have a different combo than those listed above, beats me!
Larry Fulwider