At this stage we had joined the largest pieces of bog iron into a single workpiece weighing just over one kilogram. At one end of this workpiece we designated an area for the haft hole, which was to be punched and opened up later in the process. We started by stretching the middle section of the workpiece in order to separate the parts set aside for the haft hole and the cutting edge, as this would make it easier to forge the width of the cutting edge area.
Iron shortage
Sadly, on completion of the refining process the amount of bog iron available to us was not enough for the axe to be made. To make sure we had enough metal, we were forced to add a quantity of slag-rich iron from an old fence post. This was introduced into the axe in two rounds, both times wedged into a split in the cutting edge area. Before inserting the second wedge, we forge welded the steel for the cutting edge to the outermost part of the wedge, so that it was sticking out and could make up a hardenable cutting edge. Thereafter we were able to hammer out most of the axe blade, making it thin and wide, before we finished off by moulding the cutting edge area into shape.
Had we had a sufficiently large workpiece for the axe, we would only have had to introduce a single piece of additional metal, i.e. the steel for the cutting edge. The line of the joint for the cutting edge steel is discernible on the x-ray of the original, but the design of the contact surfaces is less than clear. Generally, two varieties were used: the steel for the cutting edge was either chiselled in along the middle of the cutting edge area, where it could be pounded in like a wedge prior to forge welding, or it was forge welded directly onto the cutting edge area, but-to-but or slightly diagonally (scarf weld).
The haft hole
We chose to make the haft hole by inserting a chisel, punch and drift after the axe blade had been partially forged into shape. Alternatively, we could have shaped the haft hole at an earlier stage in the process by hammering out one end of the iron workpiece and folding it back into a loop to be securely closed by forge welding, thus forming a haft hole. Both methods appear to have been in use in the Viking Age, although the folding method may well have been the most common. It was impossible to establish with certainty which of these methods had been employed in the making of the original axe.
Problems
A bout of poor forge welding created problems for us later on in the axe-making process, and in the end we had to swallow our pride and make use of a modern welding tool and an angle grinder in order to close and make safe a couple of large cracks on the edge of the blade, and in the area of the haft hole. This was a less than satisfactory choice, but it was important to be able to complete the production of the axe.
Hardening and tempering
For a cutting edge to withstand wear, it must be hardened. This is made possible by the carbon content of the steel. The hardening process involves heating the edge area to a red heat, achieved at approximately 800°C, and then rapidly cooling it in water. These days, oil, which is a gentler cooling agent, is normally used instead, but in earlier times water was commonly employed. We were using carbon-rich steel, which results in more extreme hardening and carries greater risk of tension and cracking. Consequently, we heated the water to approximately 60–70°C, to soften the hardening process.
Hardening makes steel brittle and susceptible to fracture; it will therefore have to be softened somewhat before the object can withstand mechanical loads. This is best achieved by tempering, which involves heating the hardened area to 200–300°C. Traditionally, the blacksmith would assess the tempering temperature by looking at the colour of the oxidation on the polished surface of the steel as it changed from yellow (220°C, relatively hard), through to red (260°C) and then blue (300°C, relatively soft). The tempering process has not been explicitly described in early sources, so it is possible that incomplete hardening by so-called "slack quenching" was used, so that tempering could be avoided. Our hardening process involved a degree of "slack quenching", as we alternated between dipping and raising the axe from the quenching bath, but this was combined with a final round of tempering.
Learn how to make a broadaxe
Not long after finishing the replica of the Langeid axe we had the fortune of receiving a visit from the blacksmith James Austin. He kindly taught us his method of forming the axe eye by forge welding an asymmetrical wrap. Through his systematic work on the axe making process James has produced an instructional video on how to forge a broadaxe.
