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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The tool marks on the antique beam shown above were most liekly made using an adze or a combination of a broad-axe and adze. The flattening was not done with an axe alone, as we can see the smooth surface left by the adze on some of the beam's surfaces.
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.
Hewing a rectangular beam out of a round log was donein two steps:
Using an axe, broad-axe, or broad-hatchet, or possibly only an adze, a hoe-like cutting tool with wooden offset handle, the worker would make make a series of cuts along the round up-facing surface of a log. For those who had one, a chalk line was used to mark a straight line along one or two sides of the log to guide the cutting, and the scoring cuts would be made to about the depth of the line. With a chalk line or more likey working just by eye, the worker most often used a broad-axe or a broad hatchet to make the cuts into the log surface.
Rough scoring cuts may have been as far as two feet apart along the log surface, and were not made to the full depth of the string line or sight line that represented the desired flat surface of the finished beam. Between these scoring cuts the wood would be chipped out by prying with the edge of the scoring axe or hatchet.
Additional scoring cuts closer to the final cut-line might be made using the broadaxe or broad hatchet or possibly the adze itself, followed by additional chipping.
In a final series of cuts, the sharp adze or more often an axe, broad aze or broad hatchet was used to cut away the curled "chip" of rounded log surface cut and then the surface was "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 of a hewn beam bove, 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. You can see by the fact that some of the cut surfaces are smooth that the hewing cuts were made by an adze.
A skilled worker might use a sharp broadaxe to cut on-the-flat along the log surface to flatten it to its final face when no adze were at hand; in that case we might see smooth but more rounded-scalloped cuts, or cuts that were angled into the wood and thus less-flat along the beam surface (as the axe blade could not be swung absolutely parallel to the beam face) where the blade of the axe or hatchet flattened the beam surface to the final cut-line.
More often in Colonial America the final beam facing was peformed using an adze to smooth the surface. Had the chips just been split out of the you'd not see such flat, smooth cuts parallel to the beam face on the log face as are left by the adze.
This detail offers a very personal connection to the age of a building and to its past construction. You can actually place yourself where the worker stood to swing the tool.
Hewn beams and adze cut marks are described further at HEWN BEAMS & PLANKS
When pairs of individual timers are joined to one another with custom-fitting cuts to match their individual irregularities, most likely the European scribe rule procedure was being followed. All of the timbers were pre-assembled on the ground, scribed using a metal awl to make cut marks so that the joint would fit tightly, a hand auger bored holes for the treenail or wooden peg, and reference marks were made on each beam or post end to show the proper connection points during assembly.
You can see some of these marriage marks on the sawn beams in my photo below. Typically the marriage marks or numnbers were cut as combinations of straight lines to form roman numerals.
The marriage marks in the photo were on rafters in a Poughkeepsie home built in about 1790 and repaired in the 1980's by the editor [DF].
Square-rule construction ended the practice of custom-joining each pair of beam or post ends by cutting and joining timbers or other wood members using a uniform or standard joint shape and dimension. As with later mass-production this allowed any two ends of beams or posts to be joined together, making the numbering of mating post or beam ends using marriage marks unnecessasry. While I've read that Square-rule construction became domninant in North Ameria by 1820, I'm doubtful about how widespread it was at that time, given the many barns or other structures we date to later than that era that still used marriage marks on their posts and beams.
In Colonial North America, at least in the northeast where water power was available, water powered sawmills were in common use as early as 1620 when water powered sawmills cut logs into planks for colonial homes. By the middle of the 19th century and perhaps 20 years before the U.S. Civil War, thousands of sawmills were in operation in more urban areas. Nevertheless, in frontier areas where sawmills had not arrived, people continued to build homes and other structures from logs or rough-hewn logs as we described above.
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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