(01-24-2018, 01:59 AM)andrewjs18 Wrote: (01-24-2018, 01:17 AM)gregcss Wrote: Is the washer used to raise the gap or are they required, or both?
I think most people use the washers to prevent marks on the bottom plate from screwing the handle in too tightly:
https://damnfineshave.com/thread-o-rings...ntal-bands
Yep. That's what they do. They don't increase the gap, because they just space the head from the handle. Gap is one of these YMMV things, but it's probably about right where it is, anyway.
On a side note. Shaving geometry is complex, and not adequately characterized anywhere, from what I have seen. It's much more than just the gap, which people frequently inquire about. Shave angle is perhaps the most critical variable, but it goes on from there to a myriad. Blade exposure, span, even the shapes of the blade guard and head, all play a critical—and interdependent—role. Would make a great topic for a paper. But not by me. I've worked out a few tricks for measuring things, but most of my design is gut feeling and iteration.
To cite one example. The first prototype of the 17-4 sucked. It used a blade guard with cut outs, pretty conventional design. We removed the cut outs, and things improved dramatically. Why? The effective increased distance from the blade caused by the cut outs was funneling too much skin right into the edge. It's just not always apparent what's going wrong, though it gets better with experience. It's easy enough to design a razor that shaves decently. Getting one to shave well is trickier.