Another tool is moving into the toolbox and taking up residence. This one is a Union 42 tongue and groove plane. It was purchased to go with a Union 41 Tongue and Groove Plane I got a while back. These are functionally the same as Stanley 48 and 49 T&G planes. The Union 42 is the equivalent of the Stanley 49 and appears to be much less common that the Union 41. The Union 42 is designed to cut tongues and grooves in stock 3/8” to 3/4” thick, and centers its groove on stock 1/2” thick. These planes typically come with three blades. The normal cutters are 3/16” wide. They also came with a 5/8” wide cutter for working with wider stock. Both of my planes came without them. If you need replacement blades, they can be purchased from Saint James Bay Tool Company (use Stanley 49 blades).
Basically the fence rotates. In one position it cuts the tongue and the other it cuts the groove. I was not able to find an electronic copy of the manuals for these planes, but they are essentially the same design as the Stanley planes. A manual for the Stanley 48 and 49 can be found here.
With the Union 41. You will note that the 41 is slightly larger than the 42. This is probably because the 42 is a later model plane that the 41. It also has screws rather than the knobs the 41 has knobs.
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