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Well.....I threaded the end of a piece of .390 dia O1 drill rod, a couple observations....

March 28 2012 at 1:43 PM

Ed Canoles  (Login nced1)

Response to Need help with TX200 piston latch rod thread size.

First, a pic...........
[linked image]
Obviously, the top rod is the factory latch rod thread and the bottom is the thread that I cut using my 10x1.5mm die. As expected the thread class of my thread wasn't as close fitting as the factory TX thread, however it screwed into the piston just fine. I did an extra step that isn't on the TX piston....I cut a thread relief in the rod to create a square edge for the latch rod to "bottom out" on in the piston head. The TX piston has a closer thread fit, however there isn't and thread relief cut for run-out.

Well, I screwed my homemade latch rod blank (just a "dry run" mock up) into the piston, then spun the piston in my lathe to get a handle on the run-out. Yep, there was a bit of run-out as expected with the looser thread, but certainly within the realm of "tweaking straight". Next I screwed the factory TX latch rod into the piston and did the same "spin test". LOL.....even with the closer thread fit the TX latch rod run-out was double what I got with the die cut thread. Actually, that was kinda surprising!!

Well......on to working the uncompleted "catchey end" and currently grinding a couple bits to match the corner radius of the "catch".

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