What is a sash sawmill?
A sash-type sawmill is often likened to a mechanized pitsaw - a long straight saw that is held by a wood frame instead of sawyers, and which moves up and down on wood or metal slides fixed to posts. Rather than the bottom of the frame being held by a sawyer, it is attached to a crank by a wood arm called the "pitman". The reciprocating vertical saw cuts through the log sitting on a log carriage. As the carriage moves toward the saw, the saw cuts deeper into the log.
Sash sawmills were the first type of water-powered mills and provided a huge increase in productivity compared to the two-man pitsaw. It is a mistake, however, to simply think of sash sawmills as replacing pitsaws. Rather, these two sawing methods co-existed for centuries. The first powered sawmills were recorded in France in the late 1200s and their use spread through continental Europe for the next 500 years. Yet pitsawing persisted throughout that period and was still used through the 19th century in virtually every European region in which water- and wind-powered sash sawmills had become dominant hundreds of years earlier.
In early America when the term "sawmill" was used it was understood that this meant sash sawmill. European sawmills at the time of the colonization of America were sash sawmills, so naturally these are the types of sawmills that were first built in the American colonies in present-day Maine and Virginia. After nearly 250 years, metal fabrication advances finally enabled circular sawmills to displace the old technology in American sawmills starting in the 1840s-1850s. By the late 19th century, nearly all of the old sash sawmills were gone, although a handful (including the Ledyard sawmill) continued to be operable into the 20th century.
"One mill, attended by one good man, if in good order, will saw more than 20 men with whip-saws and much more exactly."
The quote from Thomas Ellicott about the enormous productivity advantage of a powered sawmill compared to a two-man pitsaw. Sawmills were important in early America - labor was scarce, so relying solely on human-powered sawing and hewing was a significant limit on the capacity to build wood structures. Conversely, waterpower was plentiful, especially in the New England colonies, so the number of water-powered sawmills increased and enabled the growth and spread of new colonial communities.
The earliest sash sawmills in America were a nearly unchanged technology from the first medieval and early modern sawmills in continental Europe. These mills were mostly wood framing and parts which could be shaped and assembled onsite by a millwright. The few metal components, the "sawmill irons" (including the millsaw, crank for the waterwheel, and the log dogs that fixed the log to the log carriage), required a blacksmith or a manufacturer and were imported to America (and accompanied by European millwrights) for the first American sawmills in the early 17th century.
The essential functions of a sash sawmill were listed by Thomas Ellicott, a Pennsylvania millwright, in 1795:
"The mechanism of a complete saw-mill is such as to produce the following effects, viz.
1. To move the saw up and down, with a sufficient motion and power.
2. To move the log to meet the saw with an uniform motion.
3. To stop of itself when within 3 inches of being through the log.
4. To draw the carriage with the log back by the power of water ready to enter again."
These functions were the same in colonial America and the young United States as they had been in European sash sawmills for hundreds of years. Although there were a few wind-powered and tidal-powered sawmills, the majority of American sash sawmills were on streams and rivers where the water power was converted to rotary motion by a flutter wheel.
"One mill, attended by one good man..." from Ellicott, Thomas (1795). Of Sawmills - Their Utility. Article 39 of The Practical Millwright, p. 77. (Part V in Oliver Evans’ The Young Mill-wrights and Miller’s Guide.)