Just as an example, if we take M1 fine thread as a example, it has 0.2mm pitch; so getting 1° accuracy in slot angle would require 0.5 µm positioning of the thread, which is Very Precise. I'm not sure if a CNC lathe could accomplish it with positive control of spindle angle and single-point threading, but it would be expensive. (Relevant YouTube video, where this operation uses a threading tool, not single-point:)
Check this postwhy it can't be 100% horizontal:
https://omegaforums.net/posts/1967087/
Archer ·Just as an example, if we take M1 fine thread as a example, it has 0.2mm pitch; so getting 1° accuracy in slot angle would require 0.5 µm positioning of the thread, which is Very Precise. I'm not sure if a CNC lathe could accomplish it with positive control of spindle angle and single-point threading, but it would be expensive. (Relevant YouTube video, where this operation uses a threading tool, not single-point:)
Indeed, and you would have to position the start of the thread in the case just as closely.
If we are talking about a screw down crown, you have a...
That makes perfect sense. I had never thought about it much before since my previous seikos had the S aligned perfectly, but I guess it is a luck of the draw.