How To Harden Cast Iron

In 3 gallons of clean water, mix .1/2 pint oil of vitriol and 2 ozs. saltpetre. Heat the iron to a cherry red, and dip as usual.

Cast Iron, Mixture For Cast-Iron Cylinders, Requiring To Be Hard

Twenty pounds charcoal pig No. 5, 40 lbs. Scotch pig, 300 lbs. scrap iron.

Iron, Cast, Mixture for strong and close-grained cast-iron for steam cylinders, etc. Eighty pounds charcoal pig No. 5, 1OO lbs.

Scotch pig, and 100 lbs. scrap iron.

Iron. Malleable, Cast, To harden. Mix equal parts of common potash, saltpetre, and Sulphate of zinc, and use as directed for prussiate of potash.

How To Straighten A Curved Iron Plate

Hammer it lightly with a round pene-hammer on the hollow side.

How To Mark Measures On Bed-Hot Iron

Blacksmiths frequently measure a piece of iron, and put chalk-marks where they desire to cut it. The iron may then be placed in the fire and heated to a bright red without effacing the marks.

How To Remove Hard Skin From Iron

Hard skin on iron is due to heat and friction, and may be removed by heating to a dull red, filing the surface, and putting the iron to cool in lime or ashes.

Contraction Of Wrought Iron

Wrought-iron may be made to contract to a slight extent by heating it to a low red heat, and quenching it in water. The first operation only, however, is effective. This plan is used to shorten eccentric rods, etc., to avoid getting them out of true by upsetting them with blacksmiths' tools.

Rubber Joints

In making a rubber joint, take a piece of chalk and rub it on the side of the rubber and flange where the joint is to open; and when required, they will come apart easily, and not break the rubber, although the latter may be burnt and hard. Repeat the chalking before screwing up, and you will have as good a joint as ever, and the rubber can be used a great number of times.

Driving Keys

Drive the key into the keyway to mark where it binds. The keyway should be oiled first, especially if the metal is cast-iron; otherwise the surfaces are liable to seize a cut, making it very difficult to drive the keys out, and cutting ragged grooves in both the keyway and the key. The same rule applies to crank-pins and all similar work.

How To Make Keys

These should be made to fit the keyways at a good fit on the sides without being tight, the locking being performed by the taper of the top and bottom, the amount of which should be about 1/8 inch per foot of length.

How To Ease Keyway And Slots When Hardened

Take a strip of copper and use it as a file, applying oil and fine emery upon the surface of the work.

Thickness Of Liners

To ascertain the proper thickness of a liner or strip necessary to go between a pair of brasses so that (when the faces do not meet) the liner may be placed between them and the brasses, when bolted up tight, without jamming the journal, place a piece of lead wire bet ween the brasses, and then screw the cap down tight, and the lead wire will compress, denoting the necessary thickness of liner. The latter should be made a shade thicker than the distance the wire was compressed, so that the brasses may lit without binding the journal.