The Gage self-setting planes may be one of the more beautiful planes. These transitional planes were manufactured for roughly five decades (circa 1885 to 1935). The self-setting mechanism allows the blade and cap-iron assembly to be removed, the blade sharpened, and re-installed without readjustment. (still allowing for depth adjustment). The self-setting mechanism on the Gage planes is one of the more interesting, and most of the core innovations in the mechanism occurred in the first ten years.
When it debuted in early 1880’s it was touted as being the “Only Self-Setting Plane Made”. Stanley did not have any planes with a self-setting mechanism until they bought Gage Tool Co. in 1919, and Sargent’s “Auto-set” planes did not appear until circa 1915 (at least that’s when the patent was issued). That it was attached to a transitional plane was likely coincidental, although of all the transitional blade adjustment mechanisms this was unique.
The concept for the self-setting mechanism was realized in a patent from D.A. Bridges in 1883 (Patent No. 271,569). It described an invention to “provide an efficient bench plane which can be adjusted with perfect ease to its work“. In the two patents that followed (No.323,804 in 1885, and No.339,872 in 1886), the mechanism evolved, to its apex in a patent by Stanley in 1920 (No.1,331,280), which saw the mechanism transferred to a line of metal planes. With respect to the plane bodies, not much changed in the intervening years – they all maintained a razee-type shape.
The self-setting mechanism is composed of two parts: the carriage, held within the plane body, and the cap-iron/blade assembly, held within the carriage. The construction of the carriage and corresponding cap-iron/blade assembly means there should be no need for setting the cutting edge of the tool parallel with the sole of the plane every time the cap-iron or blade is removed. If the cap-iron is removed, the blade can be taken out of the carriage, and replaced without altering its position. The blade can still be adjusted for depth of cut.
The metal carriage
The first patent, that of Bridges (No.271,569), describes a metal substructure that holds the blade adjusting mechanism in the oblique mortise of the plane body – what he terms an “inclined parallel sided throat iron“. It is somewhat better termed a carriage, and incorporates both the frog and throat assembly. Two screws hold this carriage to the plane body, and allow for it to be adjusted up and down in the mortise. This allows the frog and throat assembly to be moved up to permit the bottom of the plane to be trued up when it becomes worn. The bottom plate of the frog/throat assembly is shown in Fig.4.
The fundamental structure of the carriage changed very little over the intervening years from the original patent to the manufacturer of “clones” by Stanley for other companies in the 1920s. Fig. 5 shows the main components of the carriage from an OVB version of the Gage No.835 (after 1920).
The cap-iron/blade assembly
The original patent called for a very thin cap-iron and blade assembly with no chip-breaker present. The cap-iron has a set-screw which passes through the cap-iron and bears down on a structure known (in the original patent) as the “bit-plate” – this is essentially a clamp attached to the blade which helps position it in the carriage, and allows for depth adjustment. When the cap-iron is in place in the carriage, the screw is brought to bear forcibly on the bit-plate – raising the cap-iron, and forcing the blade down and locking it into position. The original patent also used lugs on the side of the metal carriage, and associated edge recesses on the cap-iron in order to engage and position it in the metal carriage.
Substantial changes were made to the cap-iron and blade assemblies in the patent of 1885. The cap-iron assembly is transformed into a combination of a chip-breaker attached to a heavy cap-iron (Fig.7). The method of holding the assembly in the carriage also evolved – the lugs/edge-recesses of the previous patent have been replaced by a transverse rod (Fig.5). The cap-iron has a concave round bearing with which to engage the rod. The only change in the patent of 1886 is the modification of the clamping mechanism attached to the blade. There is now a rectangular clamping plate on the upper surface (the “bit-plate”), and a guide block on the lower surface. The guide-block has a semi-circular recess in which the disk of the depth adjustment screw fits. Lateral adjustment is achieved by adjusting the clamps.
The patent of 1885 moved the plane to it’s modern form. Gone is the handle overhanging the heel of the plane, and a front knob has been added. It also included a fulcrum-bearing lever on the top of the clamping plate assembly to allow for lateral adjustment in the plane. It is likely very few if any planes based on the Bridges patent were ever made, with the planes likely based on the 1885 patent – yet I have not seen any with a lateral adjustment lever.