ASTM specification committee F16.96 (Bolting Technology) is considering sponsoring research to re-confirm/refine this equation. As I hear more about this, I will post it in this thread.
I'll address your question in two parts: in general, and for your specific situation.
In general:
There is no truely standard fastener part numbering system, but there are a number of fastener part numbering systems that can be used:
- ASME B18.24.x provides part numbering systems that allow...
I agree with the previous posters that, for a new design, you should not need washers. If you are concerned about the bearing load on your flange material, consider using a washer-faced nut instead of a regular nut.
If you are working on an existing flange joint, there are times when you need...
One concern with using the various Inconel alloys is galvanic compatability. Inconel is very noble, so you need to worry about the environment and Inconel's effects on the materials that it contacts.