Chris Schwarz of Woodworking Magazine (both on his blog and in the upcoming autumn issue) suggests it was in the late 19th century that fleam (the bevel on the face of a saw’s tooth that changes the profile from efficiently ripping to cleanly cross cutting) was added. Schwarz also makes the point that hand-filed saws inherently have some fleam, and that machine filing brought on the factory-sharpened cross cut saws. Both these last points I agree on.
My theory is from a little different perspective. I believe fleam was present on saws much earlier. In fact, I believe the practice was at least done in the later 17th century, some 200 years earlier. Why? Because the efficacy of cross cutting-shaped teeth was known and prevalent on larger saws intended for cross cutting of timber and beams by the latter 1600s. Saws intended for such usage were manufactured with fleam added to these larger saws by their makers. The inventory records for Port Royale, Jamaica, prove this point. Most likely earlier records exist as well. Even Moxon describes what can only be considered either slopping gullets or fleam angles on the face of a tooth. Which (or both) is unclear to me at this point.
So why are the texts in general silent about saws with brass or steel backs? Here’s where more of my guessing comes in. I believe that saws made for joiners and cabinet makers (a later designation) were simply made in a variety of lengths and a variety of teeth per inch in a rip-toothed pattern. I believe it was up to the individual to shape the teeth for its intended usage.
Why the difference between smaller saws and the larger ones? I do not know for certain, but from a saw maker’s perspective, I believe the difference lies in the effort to alter the teeth on a large saw versus the smaller joiner’s saws. The tooth styles on larger saws were, and still are, vastly different shapes. Not so on joiner’s saws. The basic shape of the teeth on joiner’s saws are identical, save for the amount of rake or the addition of fleam.
The era post-Civil War in America was a period of great expansion. The shear number of carpenters climbed as did furniture makers. By the last quarter of the 1800s, I believe saw makers enjoyed great prosperity, by and large, because of the increase in this activity driven mainly by the building trades. I think saw makers therefore sought a value-added approach: Now you can purchase saws with the teeth already shaped for the task at hand. I also believe this practice began prior to the advent of saw sharpening machinery.
I do not think Schwarz and I really differ much at all on this issue. I believe any apparent difference can be chalked up to the difference between manufacturing practice and shop filing practice in the centuries prior to the last quarter of the 19th century.
Take care, Mike