Hand Tools in History
Grey Iron Castings
The following article is reprinted from the Stanley Tools 1937 Tool Talks newsletter.
Only the Finest Grey Iron Is Used for Stanley Plane
Iron is one of the oldest known metals. The Old Testament records that Tubal Cain-born the 7th generation from Adam-was "a forger of every cutting instrument of brass and iron". Cast iron was first used at the close of the Dark Ages, but it was not until 1827 that a plane was made with a cast iron body, and it was not until 1858 when Leonard Bailey began that series of inventions, remarkable for their enduring merit, that the iron plane came into general use.
But back to our story-Grey Iron Castings as used in the Stanley Bailey Plane of today.
What Is Grey Iron?
Volumes have been written on this subject, but let it suffice for this issue of "Tool Talks" to say that there are different grades of grey iron. .The best grade of dark grey iron as used in Stanley Planes is made by melting pig and scrap iron, which contains silicon, sulphur, phosphorus, manganese, graphitic and combined carbons in ideal proportions. It is these elements that give the casting its distinguishing dark grey color and impart the quality of flowing freely and cleanly in the sand mold made by the plane pattern. Further, the casting is rigid but not brittle and can be machined as desired. It will take ordinary blows and bumps without damage, and will not become distorted from weather changes.
How Is the Plane Bottom Made?
Stanley Plane Bottoms are castings made by pouring molten iron (as described above) into a sand mold. To make the sand mold it is necessary to have a "pattern".
Stanley Plane Patterns are made from "ounce" metal-a mixture of copper, tin, lead and zinc. The patterns are made slightly oversize to allow for shrinkage of the metal when cooling. There are two or more plane patterns used in the same mold. Not until the patterns have been checked by the pattern foreman as correct in every detail and accurate to .002 of an inch are the patterns turned over to the foundry.
The foreman in the foundry assigns the pattern to a man skilled in making that partlcular type of mold. Some men make excellent small molds but poor large ones, or vice versa. The reasons for this are varied-temperament, dexterity, experience, etc.
The patterns are mounted on a molding machine for the molder. Let's
suppose he has been given a jack plane pattern. The desired type of "Flask",
in this case a "Box-flask" is given him. The flask is made of wood in two
parts-the lower part is called the "Drag" and the upper part is known as
The "Drag" side of the mold is made on a dummy plate. The "Cope" side is made on a molding machine. The mold is made of sand rammed by hand into the flask. The ramming of the mold is most important in order to get a clean, smooth and perfectly straight casting. The molder has to have considerable experience in order to produce castings of a quality necessary for a perfectly finished plane. To complete the mold the patterns are drawn from the sand and the two halves of the mold are joined together and set on the floor to await the pouring of the metal.
The sand used in making planes is very fine, but porous enough to allow
the gases to escape. Its two important characteristics are "Bond" and "Temper":
Bond is the ability of the sand particles to cling together. Temper is
the amount of moisture in the sand and is what determines the smoothness
of the casting.
The furnace or cupola in which the metal is melted is circular in shape, about 50 feet high, and is lined with fire brick and clay. Each morning the cupola is charged. First a layer of sand is placed on the bottom, and then a wood fire is started and placed on this are alternate layers of coke and iron. With each layer of iron a limestone flux is added which serves to keep the coke ash, sand, and other impurities on top of the molten iron. After the fire is lighted and again about 20 minutes before the metal is poured, blowers are turned on to raise the heat so the metal will melt quickly. A glance through a "peep hole" in the cupola would now show the metal dripping down over the coke and settling on the bottom of the cupola. Everything is now ready for pouring. A clay plug is used to start and to stop the flow of metal. The one in the cupola is broken for the start, and if necessary a new one can be inserted with a steel rod to stop the flow.
As the iron comes out of the cupola it is checked with a Pyrometer. Temperature checks are made at regular intervals and should range from 2800 degrees to 2850 degrees. At the same time an inspector pours a small test mold and checks it for grain structure, machinability, color and hardness.
The molten metal is drawn off into a trough which extends to the molders ladles and to "buckets" which carry the metal to molders located at some distance from the furnace. When the ladle is filled the molder pours the metal into the sand mold where it flows in and fills the impressions in the sand. The mold is then allowed to stand until the iron solidifies and cools sufficiently to prevent any distortions.
To remove all foreign matter from the castings and to show up any defects, they are either sand blasted or "pickled" in sulphuric acid. Some plane bottoms receive both the sand blasting and "pickling". Following the cleaning, each plane bottom is given a file test to make sure that it is not too brittle. All that pass this inspection are ready for the machining operations.
The high quality of Stanley Plane Castings is due to skilled workmen who take pride in making good tools, and the close control of patterns, analysis of iron, cupola charging, sand, molds, temperature, cleaning and inspections. You can sell Stanley Planes with the assurance that they are the finest planes made.