Ancient Egyptian tools
The pyramids at Giza, built by the ancient Egyptians, are made of limestone, originally with a casing of polished marble. The builders are thought to have used copper tools. Limestone has about the same hardness as copper so this would have been possible but difficult.
There is some evidence of hearths near the pyramids where, it is suggested, the masons would have reshaped and hardened the edges of their copper chisels by heating and hammering. As the limestone would quickly blunt copper tools, this must have been a frequent operation.
The Egyptians also worked granite — a much harder material than limestone — to form statues, pillars, and the like. Abandoned, partially finished obelisks (think Cleopatra’s Needle) found in granite quarries that were in use in pharaonic times show that rows of holes were bored into the rock as a first stage in extracting large granite blocks. It is not clear how these holes were drilled.
Some copper tools may have contained significant amounts of arsenic, which occurs naturally in some copper ores. A copper alloy with 10 per cent arsenic is harder than copper but not hard enough to drill granite on its own — bronze, an alloy of copper and tin, was not used until much later. A rapidly turning copper tube with sand as an abrasive has been shown to cut into granite, but it would have been hard, very slow work.
Another possibility is that the ancient Egyptians had a method of hardening copper that we don’t know about.
A few iron objects, such as knives and jewellery, have been found in very old Egyptian tombs. The pharaoh Tutankhamen had a dagger with a gold handle and an iron blade tucked inside his mummy wrappings ready for use in the afterlife. It must have been one of his most precious possessions. Recent analysis shows that the blade contains significant amounts of nickel and cobalt — which stopped it rusting — indicating that it was made of iron sourced from an iron meteorite.
up the upper part of the plane cutter. Jock tested the upper part of the cutter and measured the diameter of the pyramidal impression at 0.9mm, giving a hardness of 275HV.
The Titan Tools plane cutter had engraved on it: “guaranteed hardness tested”, but Jock couldn’t find any evidence of this, probably because honing of the edge had obliterated the testing mark.
The chisel
The ¾-inch firmer chisel was found to be very hard, and next to the pyramid forced into the bottom of the blade by his tester Jock found a tiny circular depression. This would have been the result of the factory hardness test, which would have used a hardened steel ball forced into the chisel to give a Rockwell (HR) or Brinell (HB) hardness number.
To sharpen such hard steel, something harder, such as alumina, diamond — the hardest known substance — or silicon carbide (carborundum), is needed.
Australian Dick Lynch wrote the 320-page book Collecting Titan Chisels, which, despite its rather hefty price, sold out its first edition and has been reprinted. You can buy the book from the author, who can be contacted at dicklynch43@gmail.com.
Faulty heat treatment, giving the wrong hardness and insufficient strength, is a common cause of mechanical failure. In one case the rear axle of a new Hillman Imp car broke, as did its replacement. The factory declined to pay for the repair until the owner, fortuitously a metallurgist, was able to show that the axles had escaped heat treatment and so were not up to the job.
The emphasis on the hardness of Australian chisels and plane cutters in old advertisements suggests that the local market was wary of easily blunted tools, perhaps from previous experience of tools of disappointing performance.