The following is information obtained from PATENTED TRANSITIONAL & METALLIC PLANES IN AMERICA, VOLUME I, Union Catalogs and my observations.
The Union Mfg Company was incorporated in 1866 with capital of $100,000. As the name implies it was a union of several existing businesses established to provide gray iron castings and special machine-shop work for these companies. Some of the thirty-eight original stock-holders included officers of the Stanley Rule & Level Company. Its believed the company was established to produce cast butt hinges, hitching post caps, pew rack brackets, coil door springs and household hand pumps and similar cast items. In 1880 they commenced manufacturing lathe chucks invented by James N. Skinner, and about this time they provided the castings for levels manufactured by the Davis Level and Tool Company of Springfield, Massachusetts.
On December 8, 1903, John W. Carleton and George E. Trask of New Britain were granted patent No. 746,285 for a lever-operated cutter adjustment. On this same day John W. Carleton was granted patent No. 746,286 for a plane iron fastening device to be used with this plane. These patents and other from these inventors were all assigned to the Union Mfg Co.
It’s believed the 500 series was released before the X series. They carry the type 1 markings from the X series metallics where the X series trannies do not.
The patent drawings for patent No. 746,285 illustrate both a wood bottom and a metallic plane with this feature. It was only used however on wood bottom planes. No metallic planes of this design are known to exist. The c. 1905 Union Catalog offered wood bottom planes of this type in five sizes. (502, 515, 537, 539, 542)
On June 28, 1904, Carleton and Trask were granted patent No. 763,721. This design was similar to the lever adjustment except it had a vertical threaded post with two brass adjustment nuts to control and lock the arm which in turn adjusted the cutter. It is interesting to note that the December 8, 1903 patent date is cast into the bed of all Union metallic planes of this design but the June 28, 1904, patent date is stamped on the toe of the wood bottom planes.
Both planes are equipped with a lateral lever as shown in the 1904 patent. Both wood bottom and metallic planes of this type were available in all sizes equivalent to Stanley planes and marked with corresponding numbers except the number was preceded by an X. The smallest plane in this series is marked No. O and is equivalent to a Stanley No. 1 in size. This size was not listed in Union catalogs.
The X series line of metallic planes were equipped with mahogany handles and knobs.
The way the laterals were attached changed over time as well. Some are riveted and peened and some have screws holding. I have also observed the screw sizes vary as well, even on similar size planes.
It’s interesting to note that Lakeside (a Montgomery Ward brand) is one of the few bench planes sold with Union cast in the body and only Lakeside stamped on the iron. This configuration is fairly common and new-old-stock still in the box are known to prove that was how they were sold.
Exactly when the production of the X series stopped i have not discovered yet. It’s believed that Stanley bought the Union plane division in 1920 and continued to sell Union inventory, so I would assume that the production stopped around that time-frame and sales was discontinued once the stock was used up.
The Union X series planes are harder to find than their Bailey type counterparts but they are not exceedingly rare with the exception of the X0. The X0 is similar in size to the Stanley #1 and is extremely rare and seriously collected making it quite valuable. Thanks to Robert Porter of The Old Hand Tool Shop for the following photos of the Union X0