There is a great book by Jeannette Lasansky titled “To Draw, Upset and Weld: The Work of the Pennsylania Rural Blacksmith, 1742-1935” that was published 30 years ago. We’re taking a bit from the title in the next two posts in order to begin to describe how blacksmiths fasten two pieces of metal together.
In our shop we use mechanical connections like nuts and bolts, riveting (such as the thumber riveted into the Suffolk latch), brazing, and welding. We’ve not had a need to forge weld for years in what we make. If we need to weld a part in a tool or jig, we use a MIG welder.
At the top is a Lancashire pattern die plate from the early nineteenth century. Each hole in the plate cuts threads for bolt-like fasteners. We use modern die holders with interchangeable dies for each size thread, like the half-inch dies in the center. At the bottom is a modern tap for cutting threads in a hole for nut-like fasteners. The die plate at one time also had its taps.
This is the back of the spring latch that was shown in a previous post along with a knob. The parts of the spring latch were attached to the back plate by riveting — peening, lightly hammering, the metal protruding from the hole until it no longer fits through the hole and forms a secure fastening. The lever itself is held to the back plate by peening over the edges of the boss; where the pencil is pointing. The brass knob was made of three pieces: thin front and back ovals soldered together and soldered to a turned brass shaft. The knob is held to the long iron shaft by a pin.
An important tool in our shop is the blacksmith helper — a jig holding moveable dies, one of which is struck by a hammer. We made this helper using nuts and bolts to hold the vertical parts together. These were then brazed to the base in the fire. Brazing is done by heating the iron or steel hot enough so that brass will melt when it comes in contact. Brazing makes a strong joint, much stronger than soldering, almost as strong as welding. This blacksmith helper has been in constant use for over 15 years. We’ll do a post soon on how the blacksmith helper works and the dies we use.
Forge welding was a frequently used way to fasten two pieces of iron or steel together. Forge welding is done by heating the pieces at the same time in the fire to just below melting temperature — about 2,000 degrees Fahrenheit. The pieces are taken from the fire and, on the anvil, hammer forged lightly to join them. Low carbon wrought iron welded easily without burning, unlike higher carbon steels today. This is the bottom of the large pintle shown in a previous post. The pintle and the wrapped joint are easily visible after the weld.
In the eighteenth century and on into the nineteenth, forge welding was used to attach pieces of high carbon steel to low carbon supports. This had several advantages — high carbon steel was very expensive and the lower carbon support was cheap and provided shock resistance. Plane irons and chisels, for instance, would have a small piece of high carbon steel as the cutting edge while the bulk of the iron or chisel was wrought iron. It’s sometimes possible to see in old tools the line where the two metals are welded. The high carbon steel is also more likely to become pitted with rust.
As an aside, steel around 1800 came in three grades: blister, shear, and cast. Blister steel was the cheapest and was produced as bars with a high carbon blistered outside and soft, wrought iron cores. Shear steel was used for agricultural tools and was refined blister steel. Cast steel was made by melting shear steel chunks in a crucible, making the steel uniform. Tools made using cast steel were not cast in molds as some would think. They were forged using the high quality crucible steel.