The Simplex band threading is M5X1 (25.4tpi) by my guage (a 10X1 rear axle) which is much coarser than typical M5X.8 (~32tpi) shifter screws. M5X1 bolts are not common in the US, I can tell you.
Curious, I checked the threadings of the Simplex shifters on my UO-8, which has band AND brazed (left and right, respectively) shifter bosses. Both are 25.4tpi.
I've used Simplex band clamps for Shimano SIS shifters in the past, and found the Simplex hex bolts were too short, so a 10-24 SAE screw (~9% smaller dia!) was substituted. A poor fit, but has worked for many years since the Shimano shifters require no periodic re-adjustmet as their friction (left) and indexed (right) mechanisms are internally pre-set, allowing me to use Loctite on the threads. One might alternately re-tap for a full-sized (M5X.8) bolt, but the 10-24 screw was the easier fix when using the modern shifters.
Might the different threadings reflect the designer's idea of how much twisting force on the wing nut should be needed to effect the desired level of friction? It wouldn't affect Retrofriction shifters as I believe these are of the "pre-set" friction type common to modern downtube shifters. I note also that earlier Huret shifters also use the coarser 1mm/25.4tpi threading.
David Snyder Auburn, CA usa
Brian Van Baush wrote:
In my experience the simplex bolts are metric for clamp on and braze on posts. The threading is either fine or course and the length also varies; the course threads are for clamp on and the fine are for campy standard braze-on posts.
Brian Van Baush
Seattle, WA USA