Shear-steel
The Encyclopedia of Founding (1892)
Shear-steel of commerce is classified as double and single shear steel. Owing to the imperfections of blister-steel, it is not suitable for the manufacture of cutting instrument, as shears, knives, etc., until it has undergone the processes of cutting, piling, reheating, and welding together again under the hammer or by rolling. The resultant bar is shear-steel; this, when cut up or doubled upon itself, reheated, and again hammered or rolled, is double-shear steel. See BLISTER-STEEL. Sheathing-metal is a metal or alloy which, when rolled into sheets, is employed for covering the bottoms of wooden ships to protect them from worms, etc. Muntz's metal for this purpose is copper 60, zinc 40; but he states that any proportions between the extremes of copper 50, zinc 50, and copper 63, zinc 37, will roll and work at a red heat; but copper 60, zinc 40 is always to be preferred. The cast ingots of this alloy are heated to about 200 deg. and rolled into sheets, the same heat serving for working this alloy into other shapes, as bolts, etc. Numerous other alloys are employed for this purpose, amongst which may be noticed: Mushet's--copper 100, zinc 1/8; Collins's red sheathing-metal--copper 8, zinc 1; Collins's white metal--copper 1, zinc 16, tin 16; Pope's--lead 1, zinc 3, tin 2; all of which may be heated and worked as previously described. The nails used for fastening the sheathing are composed of an alloy of copper and tin. See BRASS. Sheet Iron is rolled from the bloom direct, or from slabs and piles. It is brought to a welding heat and passed through the slabbing or roughing rolls, end and sidewise, according as it appears to require distention, until the mass has been reduced sufficiently for final rolling in the finishing-rolls where, being now brought by the previous operations to the required width, it is passed through entirely in the direction of its length. Gauges of the length, breadth, and width indicate when to discontinue rolling. The exact size is obtained by means of plate-shears. See MALLEABLE IRON.
What Has Changed in the Last Century
The 1892 account describes shear-steel as a routine commercial product, made by piling, reheating and welding blister-steel to work out the flaws of the cementation process. That whole chain is now industrial archaeology: bulk steel has been made by the Bessemer converter, the open-hearth furnace and, since the mid-twentieth century, the basic oxygen converter and electric arc furnace, in which composition is controlled directly rather than corrected by hammering. The last British cementation furnaces went cold around the middle of the twentieth century, and surviving examples such as Derwentcote in County Durham are preserved as monuments; shear steel today is made only in small quantities by heritage smiths and knifemakers who want the laminated grain. The neighbouring note on sheathing-metal has dated just as sharply, since wooden hulls sheathed in Muntz metal gave way to steel ships protected by antifouling paint.
Written for this edition, 2026.