Ounce
A division of the pound weight in English. In Troy weight it means the twelfth part of a pound, and weighs 480 grains. In avoirdupois weight the ounce is the sixteenth part of a pound, and equal to 437 1/2 grains Troy. Ovens for Drying Moulds and Cores.--Much subsequent annoyance and loss is saved by exercising forethought with regard to location, size, and style of oven when it has been decided to build a new or make extensive alterations in an old foundry. Some moulds, owing to their magnitude and form, must necessarily be built in the casting-pit and dried there. The pit becomes, in such cases, a drying stove or oven by simply closing the mouth and building open fires at convenient places on the bottom if wood or bituminous coal is used for fuel; if anthracite coal must be the fuel, then recourse must be had to extemporized exterior fireplaces, with suitable arrangements for creating a draught. It is, however, possible, in some instances, to build large moulds in sections, and by this means convey all the parts to the oven to be dried--a very superior way when it can be done. Temporary contrivances for drying small cores are to be met with in almost every foundry, from the rim and bottom-plate of the heating stove to the more elaborate device consisting of wrought-or cast-iron sides bolted together, inside of which are slides to rest shelves upon, the top having a hole with raised edge to receive a stove-pipe. The hinged door may be the full size of the oven, so as to expose all parts of the oven at once. An ordinary fire-pot, with provision for draught underneath, can be set down in the floor and this oven set over it, or the plates may be long enough to permit the fireplace to be enclosed within the structure, and thus make the oven a portable one.
Millet's patent core-oven for small cores is a brick structure with an iron front, to which is attached the necessary hinges for swinging the perforated shelves in and out. Each of the shelves works independently, and, by means of a duplicate door on the back, the oven is closed, thus retaining the heat in the oven while the cores are being loaded or unloaded. It will be seen that no heat escapes. Cores may be handled with dispatch, as all operations are conducted outside, so that both fuel and time are economized. Other excellent ovens for small cores may be obtained from the supply dealers at a very low coast, which when placed down on the floor and a pipe connection made are at once ready for use.
Steam-heated ovens are now very numerous. They consist of steam-piping laid direct from the boiler to the oven, where a valve controls the amount of steam allowed to enter a system of coils, which latter constitute the core shelves as well, being set somewhat slanting for drainage. Sixty pounds steam-pressure in the coils give a temperature in the oven of 250 deg., which is sufficient to dry ordinary cores without the possibility of burning them; an increased pressure will, of course, give greater heat. Ventilation is perhaps best secured by a somewhat loose-fitting door and an outlet at the bottom of the wall. The ordinary ovens for drying large moulds and cores are, as a rule, very defective, lacking in suitable rack and carriage accommodation,--two very important features, well worthy of more than ordinary consideration. To save the annoyance and loss attendant on moving heavy loads in and out of the oven, they may very readily be constructed of two main walls of masonry, having hinge fixings built in them on the top and ends, to which plate-iron doors may be accurately hinged. When the moulds are ready for the oven, the covers are thrown back and the end or ends opened, so that a free passage is made for loading direct from the crane to the oven, and thus obviating the jarring of the moulds which usually attends transit on carriages. Closing over the top covers and shutting in the ends converts this into an admirable oven at once, which, when the moulds are dry, may be opened again and become, as it were, part of the foundry floor, on which the moulds may rest safely until required for closing and casting. For description and details of special large oven constructed by the author, see "The Iron Founder," p.52. See also DAMPER; ROTARY OVENS.