A STAMP MILL.

Thames Guardian and Mining Record, Volume I, Issue 118, 24 February 1872, Page 3

A STAMP MILL.

A WEi,i,-known American author states that the expression “ Stamp Mill,” in a limited sense, signifies simply the batteries ; but in a broader sense, embraces not only the batteries, but the prime movers and all the machinery applicable to the reduction and concentration of ores, the amalgamation and the further treatment of the precious metals. The works to which stamps are peculiarly well adapted, is the reduction of fragmentary ores coming from the “ (Ire Crusher,” so as to pass through No. 4 or No. 5 screens. In this capacity, stamps arranged in straight batteries arc unrivalled in efficiency, durability and simplicity. To accomplish the same kind of work, many different machines have been tried, failed, and cither found their way as old iron to the furnace, or left where first reared as monuments of a sad experience.

A stamp weighing six hundred and fifty pounds, and making ninety ten-inch drops a minute, will in twenty-four hours reduce about two and one-half tons of hard rock, from and to the respective sizes named, and requires nearly one horse power for one ton of rock so reduced. The feeding of the rock into the battery should be uniform, the practical rule being to feed so, that iron to iron shall be heard as often as every tenth or fifteenth fall of the stamp. (This may do very well where pick points and gads never find their way to the stamper box, but with them occasionally, such feeding would play sail havoc with shoes and false bottoms, although made of cast steel, or chilled iron.) Looking to the erection of a stamp-mill, location is a subject of scarcely loss importance than that of determining the jiros/icc/icr value of the mineral deposit for which the machinery is intended. The site should be selected with a view chiefly to its elevation, its accessibility to the mine and common thoroughfare, and to facilities offered for fuel, timber, and water. The height of the elevation for immediate mill purposes should not be less than twenty feet ; besides, the fall below for carrying off the tailings should beat at least one-atid-a half inches to the foot, unless there may be a surplus of water.

The floors of the mill should be arranged in steps, so that the material under treatment shall pass from machine to machine through tlie series with the least handling. The foundations of all the machinery must be firm—thos; of the stamper boxes in particular. The timber is placed as to its grain—ei'her horizontal or vertical. The horizontal foundation is sometimes composed of a single timber, and sometimes of several. In either case they arc laid across mud sills, or on brick or stone work. A single timber, termed a “stamper-bed,” being employed, the stamper-boxes arc secured in their places, either by large bolts or by being let into it. If several pieces are used, they are bolted together, one piece acting as a bed for the box, and other two as side clamps. The vertical foundation is constructed in distinct sections, each of which, designed for a single box, is composed of several timbers framed and securely bound together with bolts, pegs, and hoops. In case of there being several sections, they are connected by clamps running lengthwise off the batteries. The bed-rock is usually sought for as the base of the vertical foundation, but when this lies 100 deep, resort is had to mud sills, brick, or stone-work. The end of each frame of timber should be dressed level and smooth, so as to make an accurate tit with the plained bottom of the stamper-box, which is to be bolted to it. The vertical foundation is preferable to the horizontal, for, being separate from the battery frame, the jar occasioned by tin) fall of the stamps is not communicated to the other machinery. It is also firmer, thus rendering the blow of the stamp more effective. Besides, in care of decay it can readily be repaired without detriment to the frame of the battery.

The main driving shafts is, in some instances, coupled with the cam-shaft, and in others is connected with it by means of a counter-shaft and gearing, or belts and pulleys. When the coupling is used, the cam-shaft is frequently employed as a driving-shaft for the other machinery. In case of the counter-shaft being adopted, it is usually placed at the foot and in front of the batteries, but sometimes is put from fifteen to twenty foot from them, and ten or more feet above the level of this position. Tin? connection between the intermediate and motor-shafts may be made by direct coupling or by intervening machinery. The stamps, grinders, and amalgamators, and commonly the separators arc driven by this shaft. Another counter-shaft for the orccruslicr, and sub-counter shafts, deriving their motions from the main intermediate shaft, for driving respectively the amalgamators and the concentrators, arc generally introduced. When the elevated counter-shaft is employed, the orecrusher is driven by a sub-comitcr-shaft placed on the top of the battery frame. As a general proposition the application of intermediate shafts is preferable to that of direct couplings; for in Gio former case, the batteries and the amalgamating machinery may be run or stopped at pleasure, the one without interfering with the other; whereas in the latter ease, the amalgamating machinery, receiving its motion through the camshaft, is subject to all its delays. Besides, both the motive machinery and that driven from the cam-shaft are exposed to no little wear and tear, produced by the fall of the stamps, and the concussion of the earns and discs, although much of that is saved by the use of fly-wheels on the cam-shafts. But whether it is better to put the intermediate shaft near the foot of the battery or to elevate it as described, is not fully settled. If it is placed in the lower position, its journals and bearings are liable to be injuicd by crushed ore from the battery getting into the pillow-blocks. Another important objection is, that the cam-shaft belt is rendered 100 short to secure the best mechanical results ; otherwise, ns the running machinery is entirely out of the way of the workmen, the plan seems almost faultless.