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This article describes and illustrates different types of marks found on old wood boards and beams:
adze and axe marks, hand sawn lumber, mechanical pit-sawn lumber, circular saw cut marks, and modern planed or sanded smooth dimensional lumber. We include a table of modern dimensional lumber nominal and actual sizes for kiln dried and treated wood.
We include research citations assisting in understanding the history and development of the mechanically-operated reciprocating saw or a mechanical and often portable replacement for the hand-operated "pit saw".
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Generations of types of saws used in cutting beams, and similar details are readily available on many buildings and offer both clues to building age and wonderful aesthetic detail.
Below, in rough chronological order, we illustrate different types of saw and tool cut marks in wood: adze cuts, hand sawn pit saw marks, mechanically-operated pit saw marks, circular saw marks, and unmarked, planed modern dimensional lumber.
An understanding of how hand-hewn beams were cut, for example, can permit the careful observer to not only recognize the type and age of building framing, but even to understand just where the worker was standing when a blow from a tool was delivered to a building framing member.
Adze cuts to hew a rectangular beam out of a round log were made in two steps: an adze, a hoe-like cutting tool with wooden offset handle was used to make a series of cuts along the round up-facing surface of a log.
In a second series of cuts, the sharp adze or more often an axe was used to cut away the curled "chip" of rounded log surface cut and "planed" by the adze. The axe cut was made at the base of the chip of wood cut and lifted by the adze. In our photo above, the vertical cuts across the height of the log face (red arrow) are the cuts that were made to remove the chip, while the scalloped (green arrow) or split (orange arrow) rectangular face cuts are the marks left either by the adze blade or by the splits in the wood surface when the adze-cut chip was removed.
This detail offers a very personal connection to the age of a building and to its past construction.
The saw cuts visible by flashlight on this sawn beam form an irregular "vee" shape, a clear indicator that this beam was cut by hand using a two-person pit-saw.
Our photo-left, shows a hand-sawn pit-saw cut beam or plank. Hand-sawn planks and beams are marked by straight saw kerf cut lines that include intersecting angles marking the "up" and "down" cuts made by the sawyer who stood on top of the log (the "up" cut) or beneath the log in the pit (the "down" cut).
This beam was cut before mechanical saws were available, but after hand-hewn beams or raw logs were in common use.
This places the age of this structure perhaps in the mid 1700's.
We can contrast these saw marks with the mechanical pit saw which followed, then with circular saw marks, and later with planed dimensioned modern lumber of two generations. We include illustrations of these markings and surfaces below.
Our photo (left) illustrates a wood member cut on a machine-operated mechanical pit saw. In comparing the saw cut marks on this lumber with the hand-sawn wood above, you will notice that the saw kerf marks are all vertical across the wood, all parallel, and quite regular in spacing.
Depending on the location, mechanically-operated pit saws were in use as early as 1840 (in New York), later in locations further west in North America.
Unlike the hand-cut pit saw marks in our photo above, a mechanically-operated pit saw leaves vertical saw kerf marks that are parallel as the pit saw blade was moved consistently and vertically while the log was pushed slowly through the saw machine.
At above left we illustrate lumber cut on a circular saw mill. You will see that the saw kerf marks are all rounded or curved, and parallel to one another.
Now a hand saw might also leave somewhat "rounded" saw cur marks on lumber depending on how the sawyer moved his/her saw.
But hand sawn kerf marks will be irreglular in the curvature and will not be neatly parallel to one another.
The radius of the curve of the circular saw cut marks in this beam is quite large - that is, the round saw blade marks are flattened on the lumber, indicating that this was a large-diameter saw blade.
Lumber that was cut on smaller -diameter saw blades will, of course, show saw marks whose rounded radius is smaller as well.
The history of circular saws and thus our ability to date lumber from circular saw cut marks is an open argument among experts. Ball (1975) notes claims of invention of the first circular saw in England in 1791 and still earlier reports of circular saw use in England in 1777. But the same author cites reports of circular saw blades in use in Holland in the 1500's.
A better approach in understsanding the age-significants of circular saw cut marks on timbers is to try to pin down when circular saws were in use in a specific area.
At left, an illustration from Goss' 1837 shingle saw patent.
[Click to enlarge any image]
In North America mechanized equipment use generally moved from the east coast westward. Earliest use of circular saws is likely to appear on the eastern seaboard, probably in New England, as early as 1800 (Matchell 1813, Rees 1819) but in my OPINION more commonly throughout the eastern U.S. after about 1830.
It's also important to understand that the use of axes, adzes, hand saws, manually-operated pit saws, mechanical pit saws, and circular saws would have been used in overlapping eras.
I look at the area where timbers were probably cut and the distance from that area to the nearest larger city to infer that saw cuts would have been by a portable machine used in building or in very small saw mill operations versus larger sawmills that would have moved to mechanized and faster circular saw cutting methods.
Our patent research on circular saws in the U.S. found circular saw sophistications being patented by Wisconsin inventor as early as 1877 that tells us that they were in use before that time and that circular saws were in use through the U.S. at least as far as the mid-west and probably further west.
Early stationary sawmills were most likely found in New England in the very late 1700's where they could be located by streams providing water power for mills. (Smeaston 1796).
John A. Miller's circular saw patent described his improvement as follows:
... the use of perforations through the saw, for the purpose of securing a circulation of air through the disk ot' the saw to prevent its becoming hot; also, to the form of the perforations or slots, which reduces their liability to become clogged with sawdust, Sac. When slots are employed the rear edge only need be sharpened or beveled, though there is no objection to beveling the front edge, and may be an advantage in doing so in a direction parallel with the bevel of the rear side.
It is not absolutely essential, but is preferable, that the sharpened edges of the slots should alternatethat is, each alternate slot should present its sharp edge from opposite sides of the saw. The perforations should extend from near the center about two-thirds or more ot' the distance to the circumference of the saw.
The perforations may extend in curved lines or be irregularly placed. It is desirable to have them beveled from Opposite sides of the saw alternately, so that the air will be drawn through alternate perforations in opposite directions, thus creating a circulation by which the saw will be kept cool and expansion avoided.
Our photo at left illustrates circular saw blade marks that may indicate lumber from two different sawmills or at least two different circular saws, as the radius of the curved lines appears different in the lumber at left from that at right in the picture.
Keep in mind that lumber within a single building may show a variety of saw cut mark types and ages. That is because lumber may have been re-used or may have been cut at various times and at different mills but all may have been used in a single structure.
Also a old building that has been repaired, remodeled, or expanded and extended is likely to contain wood cut at different times and using different generations of equipment and sawing methods.
Into the 1930's, dimensional lumber (2x lumber, or 2x4's, 2x6's, 2x8's etc.) was actually cut to a size quite close to its nominal dimensions: that is, a 2x4 was close to 2" x 4" in cross section.
By 1940 dimensional lumber was cut and planed to a smaller actual size. A modern 2x4, for example, is about 1-1/2" thick by 3-1/2" wide.
Our photo (left) illustrates a modern kiln-dried 2x4 wall stud, cut and planed to a smooth-surfaced dimension of 1-1/2" x 3-1/2".
Actual dimensions of modern 2x lumber vary, and vary more widely depending on whether or not the members are kiln-dried (more likely to be exact in width) or pressure treated (still wet) or not kiln-dried SPF (Spruce Pine Fir) lumber.
14 Feb 2015 Anonymous said:
Where did you find out that mechanical pit saws were first adopted in 1840? I'm looking for reference material on the history of up-down mechanical saws.
Thanks for the question about the history of Pit Saws. Here are citations giving key inventions and dates in the development of the reciprocating saw that I’ve seen as a mechanical improvement over the hand-operated pit saw described in this saw-kerf type identification and aging article. Before I wax eloquent on the pit saw and the mechanically-operated reciprocating saw (starting in the U.S.)
There is of course no single correct date for the first use of mechanical pit saws as the movement of mechanical tools in the U.S. was generally from East to West over quite a few years. I mean to say that on the East Coast, perhaps earliest imported from Europe, various tools usually appeared first.
I have to add that the relatively-straight-bladed reciprocating saw co-existed with circular saws in many areas. However I think that perhaps it was possible to drive a reciprocating saw with less speed and less energy and thus to make slower, if more easily portable sawmills with this design than by using circular saws that would have needed more power - say from a millstream.
Crosby patented reciprocating saw designs for a portable saw mill in the 1838 and 1842. Another source of my dating of the Pit Saw to before 1841 is the Wemmel patent from 1841. Also personally I have observed the saw cut marks on what other evidence argued was original wood framing in buildings I’ve inspected and dated to about 1840 in New York.
With all that whining done, it's instructive to look at early patents for patents on lumber saws in the U.S. (there is additional history for such tools in other countries of course, and one can dig up patents from the U.K., Norway etc.) The first patent granted in the U.S. was in 1790 Patent No. 1 on July 31, 1790, for an improvement "in the making Pot ash and Pearl ash by a new Apparatus and Process."
In understanding the reciprocating saw and the pit saw, here are some relevant saw patent citations from 1900 and earlier. I've ordered these with earliest lumber saw patents at the bottom of the list.
Farr, Freeman S. "Double-acting band-saw mill." U.S. Patent 640,458, issued January 2, 1900.
Shuls, Frederic W. "Set-works for sawmills." U.S. Patent 652,727, issued June 26, 1900.
Table of Modern Framing Lumber Dimensions
Kiln Dried Size
(S4S - smooth)
|Pressure Treated (wet) Size (SYP) "S4" Extended Life Lumber||Rough Cut not Kiln Dried Size|
|2x2||1-1/2 x 1-1/2||Actual size in depth (width) varies +/- 1/4"||Actual size in depth (width) varies +/- 1/2"|
|2x3||1-1/2 x 2-1/4|
|2x4||1-1/2 x 3-1/2|
|2x6||1-1/2 x 5-1/2|
|2x8||1-1/2 x 7-1/4|
|2x10||1-1/2 x 9-1/4|
|2x12||1-1/2 x 11-1/2|
|4x4||3-1/2 x 3-1/2|
|6x6||5-1/2 x 5-1/2|
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