building better turnbuckles

[Matt Sutton]

When I got my early ZB D-10 (#1008), it had standoffs for adjusting the pulls. I found them really hard to work with, and built turnbuckles and re-rodded it. It worked pretty well, but the turnbuckles I made always end up loosening (in spite of Loc-tite, nuts and spring washers on both sides, etc). I want to re-do them, and am looking for tips to make them work better. I'm very much a beginner as a machinist, so any new knowledge or angles will help.
The ones I built are made from 1/4"hex standoffs, zinc plated brass, 1 1/4" long. Originally 4-40 threaded, I drilled them out and tapped them for 6-32, standard on the changer side and reverse thread on the other.
I picked brass for the ease of machining, but maybe brass's self-lubricating properties are the problem?
I've got the taps, dies, and their reverses already.
Any guidance is much welcomed- materials, techniques, specs, etc.

Matt

[Eric Dahlhoff]

A few years ago I made myself a batch of turnbuckles using brass hex rod. Mine are tapped for 6-40, with 6-40 nuts to lock them. Never had a problem, so I don't think it's the brass.
I have had issues with rods being too skinny. The original ZB spoke ends appear to be 10 gauge. I once tried some 11 gauge spokes, but they were not consistently fat enough and the locking nuts could not grip well. For the other end I use 1/8" welding rod (like Zane did).

[Matt Sutton]

Thanks Eric!
I'm guessing that the 6-32 vs 4-40 thread could at least be part of the part of the problem. I went with 6-32 and 1/8th inch rods because it matched what was already there, but perhaps what was fine for the original stand-offs isn't the right thing for turnbuckles.
On this steel, I've got the hook-style ends made from stacked 1/8" rods instead of the spoke ends. I've silver-soldered a few new ones for a knee lever add, and they're behaving well.
I may try making new turnbuckles from longer hex-stock. The extra length may compensate for the courser thread.

[Bobby D. Jones]

They make 6-40 thread taps and dies, In both left and right hand threads. May work better for what you are planning.

A 6-40 thread on 1/8" rods gives a better smooth transition from the rod to threads. And gives easier more accurate tuning than 6-32 threads on 1/8th rods.

Wrapping threads with nylon sowing thread is 1 way to tighten threads so they do not move, But can be adjusted if needed.

[Eric Dahlhoff]

Oops I meant 6-40 !!!

[Matt Sutton]

Thanks! Eric, I think I intuited what you meant...

Bobby, I'll try that sewing thread trick. Nothing to lose, easily reversed.