. The 20th century toolsmith and steelworker; a complete, practical, and scientific book. ight blue, place the wet swab directly on the tem-pered part. This will hold the temper in check inthe centre teeth until the outside teeth draw to theproper temper. Harden and temper both ends of the hammer the TOOLSMITH AND STEELWORKER 139 same, but when hardening and tempering the last endbe careful not to draw the temper in the opposite end(which is already hardened and tempered), which canbe overcome by dipping in water occasionally. Sandstone Cutters Tools. Sandstone, although of a soft nature, diff
. The 20th century toolsmith and steelworker; a complete, practical, and scientific book. ight blue, place the wet swab directly on the tem-pered part. This will hold the temper in check inthe centre teeth until the outside teeth draw to theproper temper. Harden and temper both ends of the hammer the TOOLSMITH AND STEELWORKER 139 same, but when hardening and tempering the last endbe careful not to draw the temper in the opposite end(which is already hardened and tempered), which canbe overcome by dipping in water occasionally. Sandstone Cutters Tools. Sandstone, although of a soft nature, differs some-what from limestone, it being of a very sandy composi-tion, while limestone is in the nature of very hard properly made for limestone will remain sharp along time, but tools for sandstone wear away veryfast. The tools used to cut sandstone are practicallythe same as those for cutting limestone, the points andplain chisels being the same, but tooth chisels differsomewhat as the teeth are left flat, as shown in , while tooth chisels for limestone are filed to a. Fig. 77. Showing sandstone tooth chisel and splitting tool. sharp point. The teeth in sandstone tooth chisels areput in with a punch machine after the last hammeringis done. When dressing plain or tooth chisels for sandstone,be careful to leave them a little rounding in the cutting 140 THE TWENTIETH CENTURY edge, as these tools when cutting sandstone are natur-ally inclined to become hollowing in the centre, andmore especially in wide chisels. When tempering sand-stone tools let the temper draw to a light blue, butwhen tempering very wide chisels be careful and donot allow the temper to run out at the centre v/hilethe corners are at a straw color, as all wide tools ofan irregular shape (especially when not being hard-ened very far back from the cutting edge by not beingdipped very deep in the hardening bath) have a ten-dency to draw the temper in the centre first, so havea small swab which consis
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