Grinding mill

“ They are tempered down to a purple or blue colour. In this state they are taken to the grinder.
Grinding and polishing of cutlery.—The various processes which come under this denomination are performed by machinery, moving in general by the power of the steam-engine or water-wheel.
Grinding wheels or grinding mills are divided into a number of separate rooms; every room contains six places called troughs; each trough consists of a convenience for running a grindstone and a polisher at the same time, which is generally occupied by a man and a boy. ”

“ The charcoal is ground in a mill, either to a fine powder and sifted; or into a coarse granular state, like gunpowder, for the preparation of which two sieves are required, one with moderately fine meshes, to allow the small dust to pass through, and one with large meshes, to separate the proper sized grains from the coarser lumps. Either a corn-mill, an edgestone mill, or a steel cylinder mill, may be employed for grinding bone-black, and it is generally damped in the operation to keep down the fine dust. ”

“ Proceeding on Saturday 25th July at 5 in the morning—at six we were three miles below Neisanger’s, abreast of Old-town creek on the right, and a floating mill owned by an Irishman named Pickets. These kind of mills are of a very simple construction—the whole machinery being in a flat, moored to the bank, and the stones being put in motion by the current. They have but little power, not being capable of grinding more than from fifteen to twenty bushels of wheat per day. ”

“ The beams used for turning the mill were fitted into holes in the narrow part of the catillus as shown in the cut. The power required to do the grinding was furnished by horses or mules attached to the beams (Fig. 110) , or by slaves pushing against them. This last method was often used as a punishment, as we have seen (§§170, 148) . Of the same form but much smaller were the hand mills used by soldiers for grinding the frūmentum furnished them as rations. Under the Empire water mills were introduced, but they are hardly referred to in literature. ”

“ The old grist mill and the covered bridge are links with America’s past which, even today, have not passed entirely from the scene. Each was a part of the fabric of our young and growing nation and each made its own contribution to our progress.
By today’s standards, the old grist mill, driven by water-power and with everything except its grinding stones made of wood, is somewhat primitive. Yet even today, one must admire the fine craftsmanship with which the water wheels and the various wheels and shafts which transmitted the power were fashioned. ”

“ The grist mill represents a striking evolution in the process of satisfying the hunger of man. The Indians pounded corn in a hollowed rock which was a crude mortar. Peasants all over the globe performed the same kind of service to obtain flour from wheat. It was the earliest hand power era. The Puritans, Cavaliers and Pilgrims probably obtained their first grist in this way. They were familiar with the use of grinding stones in Europe, so it was not long before the grist mill sprang up in the first clearings. ”

“ They use a very primitive mill, constructed of a couple of ponderous mill-stones or grinding stones, the upper one of which is turned by means of a stout beam inserted into a bore in the stone, one end being secured to the neck of a mule or bullock, which walks round and round under the lash and is always blindfolded to prevent its getting dizzy. ”

“ Hundreds of feet of fuse, hundreds of detonators, and pounds of candles were thrown away. Men would climb high in the mine to their work only to return later for some tool needed, or because their supplies had not lasted through their shift. If near the close of hours, they would sit and gossip with their fellow-workmen. Drills and hammers would be buried in the stope, or thrown over the dump. Rock would be broken down with the ore, and the mixed mass, half ore and half rock, would be divided impartially and sent, one-half to the dump and one-half to the mill. ”

“ The richest portion is carried at once to the crushing mill, the poorer is thrown into another shed below, to be broken up and further picked, and the mere stones are wheeled off to the rubbish heap. The ore being broken small is thrown into the crushing mill, and passed once or twice through it, being returned to the mill by an endless chain of iron buckets, which dip into the heap of crushed ore below, and, carrying it up, empty themselves into the mill. ”

“ Twenty yards from this was a cone of black earth twice the height of a man. This was their pile of pay dirt. For five days now, they had been working on the second 35 mine of the seven. The pay dirt they had struck was not as rich as they hoped to find, but it would repay the labor of sluicing. It was growing richer each hour. They hoped in time to uncover the mother-lode. This would pay for panning and yield a rich reward.
It was placer mining. Beside the mine entrance stood a steam thawer, a coal-heated boiler such as is used for driving a sawmill or grist-mill engine. ”

“ Some mines cannot be economically operated without the treatment of the ores upon, or close to, the mining property. With certain sorts of low-grade ore, or with those kinds of ores that may be concentrated before shipment, provision should be early made for the erection of appropriately designed mills. We say the subject should be considered early, but we do not advocate the premature erection of any mill. ”

“ A gold mine now consists of a shaft or pit dug several hundred feet down into the rock, with levels or galleries running off from it and with big openings like rooms made where the rock was dug out. The roofs of the rooms are supported by great timbers. To break away the rock, the miner makes a hole with a rock drill worked by electricity or compressed air, puts powder or dynamite into the hole and explodes it. The broken rock is then raised to the surface and crushed in a "stamping mill." Here the ore is fed into a great steel box called a "mortar." ”

“ No person who has read Elliott's description of the reckless race of grinders, or the account of them in the Report of the Commissioners to inquire, in 1841, into the condition of the people in mines and factories, can see these places without a lively interest. At this deadly trade, the workmen sit at work astride of rounded blocks of wood, which they call grinding-horses, in front of their grindstones, which are fixed on axles or spindles turned by the steam or water ”

“ We are so absorbed in the tumult of mass output that we scarcely realize the part played by the old mills in rearing the cornerstone of our vast industrial activity. The phrase, “horse power,” now geared to myriad millions of units, in all likelihood, began with the horse-operated grist mill. A horse provided the power. The creaking water wheels with their rhythmic splash, were the outposts of the hydroelectric age which has harnessed rivers and falls and wrought marvels of production the world over. ”

“ The trituration is effected by revolving the stone in a large cylinder together with a number of steel balls of various sizes, the attrition of which with the rock quickly grinds it to powder of any required degree of fineness.
More mines have been ruined by bad mill management probably than by bad mining, though every experienced man must have seen in his time many most flagrant instances of bungling in the latter respect. ”

“ Upon the Rand, South Africa, a territory dominated by Englishmen, every mine is equipped with its own mill, and all notions of mining cover the inseparable idea of local ore treatment. Here, in our country, there are many, many mines which have absolutely no means of treating their own products and the managers give no thought whatever to metallurgical or milling lines. There are, on the other hand, many companies that have erected private plants at their mines for the extraction of metallic contents from the ores. ”

“ To grind their grain, the villagers used hand mills with crank and gear, or a communal mill, usually built of oak, driven by power transmitted through a solid oak shaft, banded with iron as reinforcement, to internal gear wheels of elm. ”

“ The mills have the air of being pit-head workings dealing with a cleaner material than coal. About them are lengthy conveyors, built up on high trestle timbers, that carry the logs from the water to the mill and from the mill to the dumps, that one instantly compares to the conveyors and winding gear of a coal mine. ”

“ We soon began crushing the piles of quartz that had been taken out during the winter by various miners, and tried our own rich-looking black stuff from the Keystone. The mill was run day and night. I took charge from midnight till noon and Stubbs from noon till midnight. None of the rock was found rich enough to pay for mining [Pg 94] and milling. That tried in one or two other mills was no better. General discouragement followed, and everybody stopped mining in our gulch. Some went to work for wages in other mines, to get a fresh supply of provisions, etc. ”

“ Whenever inspectors or scientific curiosity seekers visit his mill his mute workmen assume the air of being very busy, the cars laden with his so-called ‘ore’ rumble out of the tunnel, and their contents are ostentatiously poured into the furnace, or appear to be poured into it, really dropping into a receptacle beneath, to be carried back into the mine again. ”

“ When the Crushing Mill, used in Cornwall and other mining countries, superseded the labour of a great number of young women, who worked very hard in breaking ores with flat hammers, no distress followed. ”

“ Here's a mill, a swell mill that don't lack for a thing to make it well-nigh perfect. I'll tell you about it. Its capacity. Its present limit is six thousand tons dry weight groundwood pulp to the week. That's runnin' full. There's a hundred and twenty grinders feeding a hundred and eighty sheetin' machines. And they're figgered to use up fifty-five thousand horse power of the five hundred thousand we got harnessed on this great little old river that falls off the highlands. That power is ours winter an' summer. It don't matter a shuck the 'freeze up.' It's there for us all the darn time. ”

“ One man runs each of these mills. He cannot start the machinery in motion and go away, like the man who has charge of a rolling-mill, but he must stay in the place all the time, and feed the stones to the machinery that crushes them into grains of various sizes. He shovels the powder into a large hopper, big wooden wheels go around and around, and the powder passes between zinc rolls and through sieves of various sizes. ”

“ The mills in which the ores of the Comstock lode are reduced, are all built on the same general plan. When the tourist has visited and examined one mill, he has seen them all, both great and small, so far as regards the processes in use for the reduction of the ore. Some mills are more conveniently arranged than others, however, and while in some machinery is used which is somewhat behind the age, in others will be found in operation in every department machinery of the latest and most approved pattern. ”

“ By this report it will be seen that the account of the ore taken out through the Gould and Curry (“G & C.”) shaft is not handed in until the day after the work is done. The report also shows the number of tons sent to the dump of the big mill, near the mine, and the number sent to the dump of the mine to be shipped to other mills. In all departments an equally exact account is kept of all work done. ”

“ These were some of the more obvious evils which Firmstone set about remedying. Magazines and supply-rooms were locked and supplies were issued on order. Workmen ceased wandering aimlessly about while on shift. Rock and ore were broken separately, and if an undue proportion of rock was delivered at the mill it was immediately known at the mine and in unmistakable terms.
The effect of these changes on the men was various. Some took an honest pride in working under a man who knew his business. ”

“ This machine has to be kept running night and day, summer and winter, week days and Sundays. If we were running a steam-flouring mill that could never be allowed to stop, we should be careful to lay in a good supply of coal and also have plenty of grain on hand to grind, so that the mill would never have to run empty. No sensible man would keep up steam merely to run the mill. He would want to grind all the time, and as much as possible; and yet coal is a much cheaper source of power than the hay and corn with which we run our milk-producing machine. ”

“ To begin with, it is more convenient to clamp work to a horizontal table than to the vertical surface of a lathe faceplate, or, as someone has aptly said, “It is easier to lay a piece down than to hang it up.” This is especially true of the heavy parts for which the boring mill is principally used. Very deep roughing cuts can also be taken with a vertical mill. This type of machine mill is designed for turning and boring work which, generally speaking, is quite large in diameter in proportion to the width or height. ”

“ The 120-stamp mill makes such a deafening noise that there is no fear that the curious minded will cause employés to waste any time answering questions, for nothing can be heard but the rise and fall of the great crushers and the crunching of the ores. ”

“ The want of capitalists in the mine country, and of practical skill in the boring, blasting, sinking shafts and galleries, oppose obstacles to the [Pg 160] successful progress of mining. There is but one regular hearth-furnace for smelting in the whole district; and that is on the modern plan of English furnaces. There are not over four or five regular shafts in about forty mines; there is not an engine, either by horse, steam, or water power, for removing water from the mines, several of which have been abandoned on this account, with rich prospects of ore in view. ”

“ For the wet-grinders they might supply fires in every wheel, abolish mud floors, and pave with a proper fall and drain.
“To prevent the breaking of heavy grinding-stones, fit them with the large strong circular steel plate—of which I subjoin a drawing—instead of with wedges or insufficient plates. They might have an eye to life, as well as capital, in buying heavy grindstones. I have traced the death of one grinder to the master's avarice: he went to the quarry and bought a stone for thirty-five shillings the quarry-master had set aside as imperfect ”