Linkage rod thickness

[MarkCan]

All linkages that I have, left and right hand threads are 5mm. 4.9 to be exact. Yet the rod thickness is all different. Starting from 4.4mm all the way to 5.1mm, although the last one was refreshed and zinc coated so that would explain the extra .1mm. I plan on making my own connecting rods and I would like to know, what is the correct thickness?

[mdsalemi]

I plan on making my own connecting rods and I would like to know, what is the correct thickness?

Do you have a choice? Assuming you are going to use the manufactured ball end connectors, they will have a certain thread size. Cutting new threads with a die will have an optimal size rod. Too big or too small, and you may not be able to cut the threads properly.
http://www.professeurs.polymtl.ca/luc.baron/biblio/Vis_Metrique/METRIC%20THREAD.pdf

[450sl]

The thread on these rods is not cut but rolled .
That is why the diameter of the rod is smaller then the actual threaddiameter.

https://www.youtube.com/watch?v=rwArBBcUNr4

the result of this forcing process is a much stronger thread .
mark

[mdsalemi]

Fair enough but is this a process that can be done by a DIYer trying to make their own rods?

[ejboyd5]

Do you already have a left-handed 5 mm die?

[450sl]

A company who makes Wheelspokes can help.

[MarkCan]

A company who makes Wheelspokes can help.

Thank you for a good lead. I’ll keep that in mind for next time.

In meantime I got my hands on few more linkages. The measurements were 4.8mm to 4.9mm. That is very close to 3/16 (4.78mm) readily available in hardware stores.
Needless to say I picked up few. Welders rod (4.76mm), round zinc coated stock (4.85mm) and metric stainless 5mm.
Welders rod is the least consistent in thickness as well as hardness. I could feel that while cutting the threads.
Stainless got the most consistent finish. Yet it’s not easy to cut to begin with and extra .2mm makes that even harder. Than comes the yellow zinc coating.
By now you know who the winner is, yes you guessed it.
Round zinc coated stock!
Size is right on, finish is exactly what’s needed for intermittent stage and threads are tight. What else can we ask for? Oh right, price. Whopping $1.50 per foot,  🇨🇦dollar that is. 😮

Bellow is the pic of the freshly cut threads, right and left handed.

[MarkCan]

Sorry, forgot mention.
Top is welders rod
bottom zinc coated round stock

[mdsalemi]

Nice job cutting those threads!!

[Tycoon]

Mark,
Very excited to be included in your progress….we met this summer on the Ontario gathering in Niagara where we discussed you project. ( in the gardens of the Pillar & Post)
Keep the updates coming as your passion and determination has uncovered many enlighten alternatives to these tedious project issues for us all. This is what this club is all about……
Best,
Bill

[wwheeler]

If the rod was zinc plated prior to the thread cutting, the freshly cut threads will not be protected with zinc. To keep the threads from rusting you will have to apply a protectrant or have the rods re-plated in zinc.

[dirkbalter]

Generally, rolled threads tend to be stronger than cut threads. Whether the rod is 1/10 bigger or smaller imo doesn’t really matter.
If you cut a M5 or bigger thread you want the rod to be slightly smaller in order to have a good finished thread as the material while cutting will expand a bit. Again, assuming the linkage components work well I don’t think above really matters with respect the strength.

[mdsalemi]

I'm guessing here but I don't think the strength of the threads matters too much, nor does the diameter of the rod. It's not as if these rods endure undue forces. I suspect the greatest force they suffer is at the hands of someone bending them.

Perhaps a little silver grade anti-seize will suffice rather than plating the threaded ends. But who knows...Mark may very well set up a mini plating line just for this!

Yes, the welding rod might not be the best choice; but smooth uniform zinc coated steel seems to work.

Looks like he executed a solid DIY project based on the photos.