John Siemsen wrote:
(snip)
> For me, a huge part of the hobby is the aesthetic, and each to their
own. Somehow that Pave texture inspires in me a sense of ruggedness,
craftsmanship and high adventure. I can't explain why.
Chuck Schmidt commented:
(snipped) For me the reason is because you can clearly see the result of a pattern maker using a small drill to texture the inside of the mold. Old school pattern making!
Guys- Patternmaking even in the 60's was not that deep in the dark ages.
Having purchased and specified many a mold texture for metal and injection molding, the most probable answer is a pantograph machine. A master texture in oversize scale was selected, then traced onto the actual mold with a small mill bit guided by hand but not "free hand" with the panto machine set on a reduction factor. Same procedure also created the raised lettering in the pave field. Photo etching can also be employed, that technique has been around for decades as well but not likely on these parts, most likely for the typography if used, a look under a microscope would tell much.
The earlier parts looked like they used a more random master, the later used a more mechanized style, possibly as seen both employed at the same time, an easy way to keep track of the parent mold condition, for wear and or to keep up with demand, they needed multiple tools.
Shown in the images but not discussed is that in the machined region in the upper body at the pivot bolt head on the earlier examples is handled with more finesse than the later years, the transition to the "ears" that contain the pivots is kept flowing in surface, later units show more abrupt termination, less worry about the look. Same machining witness surfaces show up on the brake arms near the brake block slots.
Remember by 1972 everyone was straining to keep up with demand.
John Jorgensen
Palos Verdes Ca