Service brake rod Clevis thread?

qstott

qstott

Senior Member
While attempting to improve the braking on my 30 Tudor, I ordered some new clevises for the brake rods. They came from one of my favorite vendors. For the life of me, I couldn't get them to screw on the rods. I thought the thread pitch was 24 per inch. Even retreading them with a 5/16" x 24 tap wouldn't get them to screw on. Could it be the the threads on the rods were so worn? Anyone know the proper size?
 
I found a spare brake rod and used it instead of using a die on the threads. I finally found a posting for 2014 that addressed the issue. They are 5/16" 24 but with an "interference" pitch or something like that. The threads on my old brake rod were badly worn, and I didn't think it would hold if I ran a die over it.
 
All treads on a mod. A seem to be very tight (slightly oversize male and slightly undersize female) There are "Fits" and taps and dies can be bought to match these. To clean a male thread, use an adjustable die (split) opened up all the way. This will clean the thread without removing any metal. The use of a non-adjustable die will remove metal and recut the thread but it will be undersize. Trying the tap may or may not remove stock. Catching the debris on paper should tell you if it's cutting metal or just cleaning rust. I have recut female threads with a standard tap and not removed stock.
Terry
 
NOOOOOOO

The threads are tight tolerance. This means the threads have more overlap and fit much snugger.

You should never tap or die these threads.

I also would not recommend heating/ welding the rods, but that is another story.

I personally would only consider original hardware since they are pretty common to find. Well good rods can be a pain to find, but the ends are all over. Every car had 4 of them.

I guess using tapped threads and such will be ok, but properly restored original seems so much better just on general principles.
 
The replacement rods and clevises are standard 5/16 - 24 threads nothing special.... Any 5/16 - 24 nut will screw on them...they are not the same as the original but are just as safe...
 
Kevin, with all due respect, I disagree. With adjustable dies it is possible to clean the thread with out removing any stock. I do it all the time and end up with original fits. Lately, I've been cleaning some nuts, with standard taps, without enlarging the threads. I always put a sheet of paper under the work to catch the debris and check for metal (bright, shiny chips) in among the rust. Were I to find any, I would stop there! When I was working as a model maker, I didn't use the fits specifications. specs were given as merely "Loose or Tight". I have a Slow, progressive gain assembly for an S.E.M. that I had to scrap because it was too loose. It used a 1/4 X 40 thread. Yes, a 1/4 X 40 TPI, .025 per turn. I used a standard tap and an adjustable die. On the next one, I adjusted (opened) the die for a tighter thread , about .002-3 thousandths and it was perfect. With Mod A threads, I would open it all the way to start and close it little by little.
Terry
 
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