Appendix 3: The Evolution of Power Saws with Tilting Arbors

This entry looks, first, at the tilting arbor on a table saw, then the radial arm saw.

Today, most tablesaws have devices to tilt the blade from ninety degrees to forty-five degrees with the table, allowing the cutting of complicated angles and miters. Some table saws still feature tilt-table assemblies, but by and large table saws feature tilting arbors. Generally, it is agreed upon that the tilting arbor outperforms the the tilting table.

(For ripping a workpiece, with the table at a 45 degree angle, and contending with the saw's fence set below the blade can cause problems, can be dangerous.)

The few saws that still use tilting tables (Shopsmith, Supershop, and the Austrian Inca -- the latter is no longer on the market) do so because they are multi-purpose machines, needing also to accommodate other accessories.

Tilting arbor

The arbor is the shaft extending latterly out of the motor, on which the blade is mounted. The arbor can be set to cut angles -- from 90 to 45 degrees -- with the table remaining horizontal. The use of trunnions in a tilting-arbor saw allows the axis of blade-tilt rotation to be coplanar with the tabletop.

("Coplanar" means "lying or occurring in the same plane; used for points, lines, or figures.")

The Trunnion

Click on the link below for the Patent record on DatAmp: 

The tilting arbor assembly is called a "trunnion". the illustration below is a view from underneath, looking up toward the bottom of the table of a tablesaw.


According to OWWM's Jeff Joslin, 4-12-05, the use of trunnions in a tilting-arbor saw allows the axis of blade-tilt rotation to be in the plane of the tabletop. John Connell (of the firm of Connell & Dengler in Rochester, NY) patented such use of trunnions in patent 210,100 (1878-11-19).

Connell uses the term trunnion in the patent specification, but in a different way, however. What we would call a "trunnion" he calls a "hanging frame" with "tongues and grooves". He says, "Trunnions might be used in place of the tongues and grooves a and b, as described, upon which we pivot the hanger frame C; but as they would necessarily project above the plane of the upper surface of the table, and be in the way, I prefer to use the tongues and grooves aforesaid."

As far as I can tell, the difference is that cannon trunnions are solid cylindrical pins that fit into semi-cylindrical depressions, whereas tablesaw trunnions are arc-shaped brackets with grooves in which arc-shaped tongues are engaged. Given all the different words that could have been used (gudgeon, pin, axle, pivot, pivot, crescent, arch, bow, etc.), the choice of "trunnion" is an interesting one.

Joslin, notes that there is "an earlier usage of trunnion than Connell's. Leonard Howard of St. Johnsbury, VT, received an 1876 patent for a tilting-arbor saw for mitering":

"This bearing rocks on its trunnions with the arbor in such a way as to tip the saw from a perpendicular plane to the angle, if desired, of forty-five degrees."

Howard's trunnion is located at the end of the arbor opposite the blade; close to the blade he has a simple pivot point, which defines the axis of blade tilting.

Adds Joslin, "These are the earliest mentions of tablesaw trunnions I have seen."

1920s: J D Wallace no 8 wallace portable universal saw ("operates on Electric Light or Power Circuit") see this 1926 pdf catalog -- print outs in folder under wallace

1931: American Saw Mill Machinery tilting arbor table saw:

1930s: [01/01/2005 The Amateur Woodworking Movement in America:] Tilting arbors (on delta’s unisaw) didn’t appear evidently until the mid-30s (still have to research this, though). [first correspondence from keith bohn on unisaw and introduction of 12" bandsaw]. October 1938 picture from deltagram.—deltagram was introduced in 1932.

1930s: Boice-Crane catalog: Boice-crane catalog K-2 1935, p. 5:

Tilting-Arbor or Tilting Table -- Which is Best?

Performance and Convenience on Every Cut is Real Factor to Consider

Boise-Crane Tilting-Arbor Saws are now in their fourth year of production. In those four years, thousands of them have been installed on every conceivable kind of sawing job, in large shops and small. Most of them have been selected only after a thorough investigation of both types and many makes. Owners are so enthusiastic about them that they recommend them to their friends and fellow manufacturers every chance they get.

We don't claim to have built all of the saw tables sold during these four years, but we do say that when the prospective purchaser fully understood what the Tilting-Arbor saw would do, and what others won't, his selection was invariably a Boice-Crane Tilting-Arbor. The improved 1935 Tilting-Arbor Saws are still better than their predecessors, offer many new features.

In order that everyone, including those not so familiar with circular saw table design, may know just what the differences are between the two types, we endeavor to show below just what each one will do IN USE. In other words we believe that your selection should be based on PERFORMANCE on EVERY TYPE OF CUT, and "with your eyes open."

Consider Facts--Study The Comparison Below

Maybe your work up to now, or that planned for the near future has not included a single bevel cut. If not. your work is an exception, for there are not many shops or many projects that do not require a taw that will cut bevels. Although Boice-Crane builds the only bench Tilting-Arbor Saw, most other saws are Tilting Table. indicating that all manufacturers make their sews to cut bevels, because no craftsmen would want one that didn't.

So we come to the next factor as to HOW the two types cut bevels. And when you understand the HOW of it, you will understand why most woodworkers and plants choose the Tilting-Arbor.

Consider the comparison below of the respective methods used in bevel ripping on Tilting Table and Boice-Crane Tilting-Arbor Saws. It makes no difference whether the bevel cut Is ripping or cutting off, whether the stock is long or abort. the same comparisons told.

The Tilting-Arbor Way

1. On the Boice-Crane, you tilt the saw to the 45° bevel. The table remains level in one position for feeding any piece.

2. You lower the saw to just cut through the thickness of the material. Table of saw remains unchanged in respect to a table position extension or permanent rest used to support long lumber. No interference ever occurs. Any table extension can be heavily constructed for permanence.

3. You adjust the fence (on either side of saw) to the width wanted. There is no strain on fence as the table supports the entire weight of board.

4. It is now extremely easy and most convenient to feed the board, on a level table, past the saw.

5 At the completion of the cut, the main piece that you hold in your bands can be removed from the table at once. The other piece (or scrap), even if not held, will remain stationary on the table beside the saw blade, and will not be "kicked back" at you.

The reason why is simple. The scrap piece always rests on the level table and does not by its own weight lie against the saw blade after completion of the cut.

The Tilting Table Way

1. Sawing on a Tilting Table Saw entirely different. Here you tilt the table to 45°, an awkward position for feeding any piece.

2. You elevate the table on many makes of saws. Table of saw is now so changed in respect to a non-tilting table extension or permanent rest that interference results, and need be removed. Extra large trunnions are required to carry big, tilting table extensions. [The trunnion is the assembly that holds the saw's arbor to the underside of the saw table.]

3. In adjusting fence to width of cut. fence can only be used on the lower side of table, as fence must support and prevent board from skidding down the tilted table.

4. The feeding of boards is not nearly as convenient as on a level table.

5. At the completion of the cut, during the time you are removing the main piece, the other piece (or scrap) will have slid down the tilted table against the rapidly revolving blade, and will invariably be shot forward. against and quickness of it will startle the most experienced wood-worker, and in careless moments it is apt to cause an accident to you, or to folks watching.

When cross-cutting the end of a short piece at a bevel, the very same comparison applies. The Tilting-Arbor Saw leads every time in convenience, versatility. and in safety. All this enables the user to concentrate fully in doing the job to precision measurements.

It is obvious therefore, just why the Tilting-Arbor Saw has the unqualified approval of wood working industries, small shops, and of home craftsmen.

Boice-Crane Patent Covers Basic Construction—And Bars Imitations

The original Boice-Crane: Patent (No. 1,922,151) broadly covers the basic principles of Boice-Crane Tilting-Arbor Saws. The manufacturing of many thousands of them under the protection of the patent enables us to give you extremely high value at lowest possible cost.

You might ask. and fairly too, "Why don't other manufacturers use the Tilting-Arbor principle in bench saws?" They don't, we believe because it would cost thousands of dollars extra to develop the idea, and even then any other different construction (designed around our patent) would be too expensive to manufacture. We further believe such a product would be unable to compete with the low-priced, high quality, Boice-Crane Tilting-Arbor Saws.

As a result, the only, wholly efficient, belt-drive, Tilting-Arbor Saws on the market for the past four years are BOICE-CRANE. Based on these facts, we sincerely believe that your money will buy more in a Boice-Crane Tilting-Arbor Saw than in any other bench saw. Among our models. you will find a most excellent machine at a price you can afford.

Source:  Boice-crane catalog K-2 1935, p. 5:

Sears Introduces Its 8-in Tilting Arbor Bench Saw in 1937

By the mid-1930s, home shops were being fitted out with tilting arbor circular saws, all-be-it compared to today, scaled down. For example, the 8-in Sears tilting arbor bench saw -- advertised with a big ad and image on page 66 of the March April issue of Home Craftsman -- splashed onto the home workshop scene. And HC itself got into the spirit by presenting a two-page spread of photos, with captions, showing several "tricks" that the tilting arbor saws could do to help amateur woodworkers achieve better results with their projects. Unfortunately, with the small size of and lack of clarity in the HC photos, readers had to resort to their imaginations for visualizing much of what these demonstration photos depict.

Why Did Fitting Out a Delta Table Saw With a Trunnion Take So Long?

Click here for patent for unisaw filed by the Inventor: Herberet E. TAUTZ, for the Assignee: The Delta Manufacturing Company

other Delta Manufacturing Patents to look at are:

As advertised in the Deltagram October, 1938 page 100. Seven years later, in Deltagram 17, No 2 1947-1948, page 159, there is a photo of a Unisaw in the basement workshop of the national radio star, Bob Burns, and in an even later 1948 issue, an advertisemnt for the scaled down, "Junior Model Unisaw", which features an 8-inch blade.

This is what happens, it seems, when you put a new product on the market in war-time. Everybody is just too occupied with activities associated with the mobilization of the war effort to pay attention to new products in an industry not directly associated with discharging the needs of the nation's war deployment.

The text in the image that shows the "new" Delta Unisaw is reprinted on the right, below, with some editorial highlighting, designed to show what Delta officials considered significant about the Unisaw:

Get Behind a Real Saw!


FUTURE years may bring forth a new and improved circular saw, but it is difficult at this time to conceive anything which might be added to this saw to improve its appearance, performance or construction. The new Unisaw is not a machine thrown together during the lull between seasons, but a power tool developed after seven years of patient experimental work.

Model after model have taken shape in the Delta experimental laboratory, only to be discarded as "bugs" and weaknessess in tilting arbor designs became apparent.

Now, however, Delta presents a new tilting-arbor, saw perfected at every point with none of the flaws of existing designs -- a saw that offers numerous exclusive advantages and an operating efficiency never before attained.

Get behind this new saw now on display at your nearest dealer

see with your own eyes the smart appearance ot the cabinet-type housing

feel with your own hands the smooth gliding action of raising and tilting mechanisms

satisiy your own mind on vibrationless performance by making a trial cut

In every way, the new Delta Tilting-Arbor Saw stands up.

You owe it to yourself to investigate the many advantages oi this remarkable tool.

The invention of the radial arm saw heralded a variation on the concept of the tilting arbor

To begin, the impact of the appearance of the radial arm saw caused considerable discussion: for some details on the radial arm saw's history, click here for the glossary entry on the radial arm saw and here for Document 46, William W. Klenke's 1930 article, "Machine Sawing From On Top")

Sometimes simply called "radial saw," it is a saw with the blade and motor mounted above the work surface and used primarily for Crosscutting and Dadoing.

(I have two vintage machines: a 1950s vintage  "double arm" Delta, and this Dewalt 12" GP model.)
dewalt gp ras

Today, the radial arm saw is largely replaced by the Compound Miter Saw.

However, because it excels at dadoing, many radial arm saw owners, if they have the space, continue to use this saw, And, for shear enjoyment, Wally Kunkel's book, How to Master the Radial Arm Saw is both a delight to read and an expert's introduction to the versatiltiy of the radial arm saw. 'Tis a pity that it is not digitized and online. If buying a copy online isn't a good option , borrow a copy through your local library, because it is definitely worth a read.

The Injection of the Term "Radial" into "Radial Arm Saw" is a Mystery

In submitting his patent (patent # 1,528,535 ) for the saw in 1925, Ray Dewalt did not use the term "radial", but instead "rotatable".

As a label "radial arm saw" did not appear until around 1930, but the use of the term is too obscure to make it worthwhile recording it on this page. Using the Google Books Search engine, a search between 1940 and 1945 yields a few hits, but it is in the last half of the decade where a large number of "hits" result.

What is more interesting about the appearance of the radial arm saw in the 1920s is that evidently it wasn't seen as a "tilting arbor" circular saw.

Patents held by Raymond DeWalt:

Use this link for a five-page patent office record, consisting of text and two excellent images

Click on the link below for the Patent record on DatAmp:

Generally recognized as the leading champion of the radial arm saw, specifically the Dewalt radial arm saw, Wallace Kunkel, extolls the usefulness of radial arm saws in his 1997 ring-bound book, How to Master the Radial Saw. Another Dewalt Radial Arm saw book is Robert Scharff's Easy Ways to Expert Woodworking

For more on the Radial Arm Saw, click here