Why would a hand awl break while stitching rubber where a machine awl--which is not significantly heavier, if heavier at all--not break?
How is it that a workshop that consists of "hand workers only" is not able to stitch evenly and consistently using tools with which they presumably have years of experience and skill?
Machines actually have a slightly harder time sewing evenly and consistently in rubber simply because the two materials--the leather welt and the rubber outsole--are different densities and different firmness. The rubber is softer, yet two or three times thicker, and it feeds unevenly relative to the leather.
The real problem with hand sewing rubber (Carreducker had a blog entry about this several weeks ago) is that the rubber closes up when the awl is withdrawn and it makes feeding bristles difficult. That said, a hooked hand awl could be used...but then what you end up with is structurally no different than a "machine stitch"...not a shoemaker's stitch, at al
According to both Vass and Daniel Wegan at Gaziano & Girling it's the awls that has been the problem for them. Daniel Wegan has expressly said that "awls breaking" was the problem, Vass just mentioned the awls and I didn't ask more than that.