The question is: why are shaving razors these particular dimensions?
A straight razor length is 11.5 cm to 7,6cm (4.5″ to 3″)
The classic safety razor cutting edge is 3.6 cm (1,4″)
The “disposable” blade is 3,5 cm (1.3″)
Let’s forget about the
straight razor and focus on the disposable blades.
At sometime in shaving equipment manufacturing history, a decision was made that a blade should be the current length. This goes for shavers designed for men and women.
What is the criteria? There must be some average used, but on what criteria was it based? Might it have something to do with an adult male’s average chin width or nose width above the upper lip? If so, why should “men’s” and “women’s” razors, intended for different purposes, share the same or very close to the same length? (I trust that few women shave their faces, but I may be out of the loop on this)
I doubt that when the “safety razor” was invented in the early 1900s extensive testing was done on volunteers to determine a blade length which was neither too long nor too short. Gilette currently employs 500 design engineers and a portion of them work on new shaving projects.
Here is a link to a video on the manufacturing of razor blades(Klik). No answers but interesting to a point.