Broken Letterpress

A skilled welder or black smith should be able to forge-braze the pieces back together, and properly done it should be as strong as before the break. Some welders can TIG weld cast iron, but the internal stresses of localized heating can also introduce new weakness.

welding antique cast-iron takes a good understanding yes skilled. or call it a parts press always ship bigger presses on a skid. I pay the pros too, taking press apart and putting pins in part to hold in perfect position for person welding.
keep looking around for a parts press you can get that part from there is some variation in size over the years.

Welding and/or brazing is an option.

Two potential problems with this type of fix. 1. Welding tends to pull carbon from base metal and into the weld, changing the chemical makeup of the cast iron. 2. Localized stress is built up in the piece as it cools. This can be overcome to some degree with proper preheat/post heat cycle in heat treat oven, if part will fit.

If I were doing the repair I would use a product from locknstich. They have a special tap that forms threads with a hook cross section and also does a counterbore on top. Tap with their special tap and install their threaded anchors and tighten until the head shears off. It will be flush with part being fixed. Do that in an overlapping pattern, and lightly peen surface when done. The special threads actually draw the 2 parts together and the joint is stronger than original part.

It is not the cheapest fix, but I have had good results using their method.

Marshall

If you are any where near Milwaukee, Wisconsin, we have some Very good cast welders here. They have repaired several plates for me.