Identifying Saw Marks
Identifying Saw Marks on Boards
Boards sawn on a sash sawmill have straight saw marks at a right angle to the length of the board. The key feature is that saw marks are very evenly spaced since the saw carriage moves a fixed amount between each saw stroke. The saw marks typically show spacing of 1/8 to 3/4 inch depending on the size of the log, and the hardness of the wood (which varies with species and moisture content). Boards sawn on a bandsaw mill have straight marks similar to up-down saw marks. However, the spacing between marks from a bandsaw is more uneven than an up-down saw since the thin bandsaw blade can flex and then jump ahead more readily than a thick, rigid up-down blade. Sash-sawn boards are easily distinguished from the arcing saw marks on wood sawn by a circular sawmill. When rough lumber is planed to make material for paneling, window frames, baseboards, etc., the sawmarks are usually removed from the surface that shows.
The saw marks on an old piece of lumber can give information about the type of mill that was used, but using the marks for dating the board needs to be done with great caution since periods in which different types of sawmills were used overlap by many decades in New England and elsewhere. Here in the southeast corner of Connecticut not far from Ledyard, the diary of Joshua Hempstead of New London, Connecticut mentions “saw pitts” in 1741, but also mentions sawmills as early as 1718 (and there is documentary evidence that the first sawmill in the New London area was built in the 1650s).
Boards sawn on an Up-down (Sash-type) sawmill have straight saw marks at a right angle to the length of the board. The saw marks are very evenly spaced since the saw carriage moves a fixed amount between each saw stroke. (1/8 inch between each stroke for this board sawn at the Ledyard mill.)
The stub shot is a tell-tale sign of lumber sawn on a sash sawmill. The stub shot is the split wood on the last few inches of a board which show that the board was not sawn through the end of the log, but rather the last few inches were split off. The stub shot sometimes still remains on timbers or boards in old buildings that are not show surfaces.
Why not saw through the end of the log? A wide piece is more stable on the head and tail blocks. Individual boards are split off after the log is cut multiple times leaving a series of kerfs. (The kerf is the slot in a piece of wood created by sawing.)
Another interesting type of mark is occasionally found in boards sawn on a sash sawmill: wide-spaced, angled marks caused by one or a few protruding saw teeth scratching the surface of the just-sawn board as the log carriage is reversed with the saw still going up and down. Reversal of the direction of the marks is from the change of direction of the saw. These marks are made more prominent by the just-sawn kerf closing up behind the blade due to tension in some logs.
Boards sawn on an circular sawmill show the curved marks expected from a round saw blade.
Boards sawn on an bandsaw mill have straight marks similar to up-down saw marks. The spacing between marks from a bandsaw is more uneven than an up-down saw since the thin bandsaw blade can flex and then jump back more readily than a thick, rigid up-down blade.
For these two bandsawn boards, the example on the top shows marks that are fairly even, but a close examination shows that the spacing is not identical. The example on the bottom is more clearly bandsawn with uneven spacing between the saw marks.