Hanging the millsaw
For proper operation, the millsaw needs to be fastened and aligned correctly in the sash, or gate. This is referred to as hanging the saw.
Fastening the saw to the frame.
Lug pins pass through holes in the top and bottom of the saw to allow it to be stretched between the stirrups. Large nuts on the top stirrup allow the saw to be tightened.
Other means were sometimes used to fix the saw to the frame. Some saws had metal plates ("tabs") riveted to the ends of the saw which caught metal hooks on the frame.
Align the saw to be parallel to the sliders
The distance from the saw to the edge of the sash is adjustable with wedges on the stirrups and set screws in the stirrups which press against the saw.
A simple gauge stick is convenient to compare the distance from the top and bottom of the saw to the sliders (also called friction rods). The wedges and set screws in the top and bottom stirrups are adjusted so the entire length of the back of the saw is equidistant from the sliders.
Adjust the rake of the saw.
For the millsaw to cut correctly it is tilted (raked) slightly in the direction of the tail block. The saw cuts on the downstroke and the log carriage moves on the upstroke, therfore, the upper saw teeth must be further forward than the lower teeth for the saw to run smoothly and not drag on the upstroke.
“…this is to give the saw liberty to rise without cutting; and the log room to push forward as it rises.”
The Young Mill-Wright and Miller’s Guide (see references below).
We use a plumb bob to measure the rake from top tooth to bottom tooth to adjust the overhang (rake) so that upper teeth are 3/8” - 1/2” further forward than the lower teeth.
The desired degree of rake is dependent upon the amount of log advance on each stroke – a larger advance of the log carriage on each stroke will require more rake. On the Ledyard mill we typically saw with the smallest log carriage advance: one tooth on the ragwheel ratchet which moves the log carriage 1/8 inch per stroke. This requires 3/8" rake (top tooth to bottom tooth).
Line up the saw with the path of cut to remove twist.
The saw must be hung straight without twist, so as it moves up and down through the kerf it reciprocates freely.
The set screws in the top and bottom stirrups allow alignment of the top and bottom of the saw so that the entire blade is parallel to the path of cut. (Some mills have only wedges, not set screws to adjust for twist.)
We first fix a marker nail in the carriage tail block at the point where the saw meets the tail block. A string is looped around the saw with both ends tied to marker nail in the tail block.
The string lying along both sides of the saw readily shows whether the blade is aligned to the tail block nail (and, therefore, the path of cut). We check for twist at the top and the bottom of the saw.
Learn more about hanging millsaws
Craik has written a good, practical discussion of the methods to hang the saw properly. Craik and Ellicott/Evans are the two key sources for the practical methods we use at the Ledyard Up-down Sawmill to hang the saw. See more about Craik in 19th century references.
Ellicott has only a brief mention of hanging the saw specifying that the top end standing about a half inch more forward than the bottom (p. 83). Oliver Evans has a short addendum on p. 90 of part 5 which incudes a paragraph on hanging the saw with very useful detailed instruction. See more about Ellicott in 19th century references.
Parsons has the best discussion of how much rake to use.
Scientific American correspondence from readers on filing, setting, and hanging a sash saw, 1860.
Correspondence from Wm. Buxton in the July 28 issue describes his experiences in filing, setting, and hanging a sash saw. Followed in the other three issues by disagreements regarding Buxton’s original letter and with each other. Very useful for the modern sash sawmill operator to see these different viewpoints about sash sawmills.
Copies of Buxton's note and replies are here.
Scientific American, 1860, July 28, new series vol 3(5), 66
Scientific American, 1860, Aug 18, new series vol 3(8), 117
Scientific American, 1860, Sept 1, new series vol 3(10), 148
Scientific American, 1860, Dec 1, new series vol 3(23), 356
These and other useful writings about sash sawmills can be found on the 19th century references page of this website.