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Mechanic's Tools and Their Makers

  Making Cold Chisel by James F. Hobart, February 07, 1885 1 of 2  

Years ago the machinist appreciated a good cold chisel. He had to do all his heavy planing and shaping with them, and he took care to have the best and keep them in shape. If a man was going to chip the teeth of a big bevel gear, in order to remove the scale, he would be pretty apt to look around for the very best cold chisels he could get hold of, and then he would keep them sharp.

When you make a cold chisel, get a good quality of octagon cast steel. It is a pretty good rule “to sample all the tool steel that comes into the shop and make cold chisels of the samples.” If steel will stand the cold chisel racket, it is good enough for any tool.

Our grandfathers used to test all their new steel by drawing a piece of it down to an eighth of an inch square, and then taking a very strong heat, in fact, burning the extreme end. Then they cooled and broke in pieces with the hammer.

They had a chance to see just how much heat it would stand without getting “rotten,” also at what heat it would harden, and whether it would spring in hardening.

Nobody knew then what a piece of steel would be like until he had tested it. It “might harden, or it might not.” Now-a-days you get the same brand from the same maker, and are reasonably sure of getting the same steel, but there is a difference, as the tool maker often knows to his sorrow.

Don’t try to draw steel to smaller sizes in hope of improving the chisel by “hammering.” “Hammered” steel now-a-days, when that hammering is done by the smith on his anvil consists of “more talk than cider."

The old chaps long ago used to improve the steel of their time by judicious working and hammering, but tool steel of to-day is so homogeneous that I would rather take it in the bar than after the smith has “monkeyed” it. Don't try to work a cold chisel too cold. There is a saying that the “devil gets the smith who hammers cold iron, or hot steel,” but don’t hammer a cold chisel after it is cold. You may hammer it enough to get hammer marks out, but don't try to draw cold steel.

I have seen smiths heat a drill or chisel for about 3/8", and then strike 300 pound blows to draw the steel, just back of the hot place. It causes terrible strains in the chisel, and if a fire crack comes in and about half the width of the chisel breaks off, they pitch it into the scrap heap or tail-race and cuss the man that made “that poor steel.”

Everybody writes in the papers against heating steel too hot, or “burning it,” but half the trouble with cold chisels is caused by too little heat. Cannon will be destroyed in time by the action of blows struck by the exploding powder.

How long would one last if it were put under a big 100 ton steam hammer and struck hard enough to disarrange the structure of the iron or steel?


You would not have to fire it many times after such treatment before it would “let go” and kill at both ends.

Heat steel as hot as it will bear, and work it while hot. If you wish to work 7/8” of the end of a chisel, do the heating back of where you intend to hammer. Heat an inch and a half of the tool. It takes a trifle longer, but you can work it much better. It will hold the heat and work easy.

Don't try to temper a chisel with the remains of the forging heat. Use a fresh heat, for tempering, and heat enough to harden. Leave all tempering “medicines” for somebody else; if you cannot get a temper with good fire and water, you have mistaken your vocation, and had better try some other track.

When tempering cold chisels, or any other steel articles, heat to a very dull red and rub with a piece of hard soap, then finish heating and harden in clear, cool water. The potash of the soap prevents the oxygen of the atmosphere from uniting with the steel and forming rust or black oxide of iron. The article will need no polishing to enable the colors to be seen. This will be appreciated when tempering taps, dies, or various complex forms not easy to polish.

Never “upset” a cold chisel. It is sure death to the steel. Many of us have lived on a farm and know something about a bundle of nice, straight, clean straw. If you work it intelligently you can tie it up into stout bands for binding other bundles.

You can take hold of the ends of that straw and draw out a handful without harm to the straw, After you have drawn out half that bundle a foot or so, try to drive it back; every blow breaks the straw, cripples and doubles it up, and it will hardly bear its own weight, to say nothing of making a band for other bundles.

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