Grinding stone

“ The grinding-stones met with in Denmark and Scandinavia are gene- rally of compact sandstone or quartzite, and are usually of two forms—flat slabs, often worn hollow by use, and polygonal prisms smallest in the middle, these latter having frequently hollow facets in which gouges or the more convex-faced hatchets might be ground, and sometimes rounded ridges such as would grind the hollow part of gouges. ”

“ After grinding, whet the edge thoroughly with a fine whetstone until the scratched effect caused by grinding has given place to a smooth surface and a clean keen edge. If you do not whet it after grinding, the edge will crumble away and the ax will cut "dead."
The first grinding will tell you whether the ax is hard or soft. You can tell by the sound of it and by its grip on the grindstone. If it is soft it cuts rapidly, grips the stone hard and gives a dull, dead sound. If hard, it gives a ringing sound and the stone glides smoothly under it, cutting slowly and wearing the steel bright. ”

“ The device saves a good deal of hand work in the preparatory stages of grinding, although it can be used only with soft stones.
Grindstones and Tool Grinding.—The general characteristics of grindstones are as follow:—
For rapid grinding a coarse and an open grit is the most effective. The harder the grit the more durable the stone, but the liability of the stone to become coated or glazed with particles of the metal ground from the work is increased. With a given degree of coarseness a soft grit stone will grind a smoother surface than a hard grit one. ”

“ Closely allied to the process of grinding is that of sawing stone. It is however rarely, if ever, that in this country any of the stone implements show signs of having been reduced into shape by this process. Among the small hatchets in fibrolite, so common in the Auvergne and in the south of France, and among the greenstone, and especially the nephrite celts found in the Swiss Pfahlbauten, [82] many show evident traces of having been partially fashioned by means of sawing. ”

“ The wet grinding is done on stones which vary in diameter from 11⁄2 to 12 in. according to the concavity of surface desired (“hollow-ground,” “half hollow-ground,” &c.) . “Lapping,” which is the first stage in polishing, is performed on a wheel of the same diameter as the wet-grinding stone. The lap is built up of segments of wood having the fibres towards the periphery, and covered with a metallic alloy of tin and lead. The lap is fed with a mixture of emery powder and oil. ”

“ Flat grinding-stones of smaller dimensions have been found in the turbaries of the Somme and in the Camp de Catenoy. [12] A narrow sharpening stone 5 inches long is recorded to have been found with stone hatchets and other implements in the Cueva de los Murciélagos, in Spain. [13] Polissoirs have also been observed in India. [14]
The Carreg y Saelhau, [15] or Stone of the Arrows, near Aber, Carnarvonshire, has numerous scorings upon it, a quarter or half an inch in depth; and, though doubtless used for sharpening tools and weapons of some kind, it seems to belong to the metallic age. ”

“ The blades of table-knives are ground on wet stones, the grinding stone being suspended, for that purpose, in an iron trough filled with water to a [185] sufficient height to make the surface of the fluid just touch the face of the stone. The grinding stones, as well as the glazers and polishers, are turned by machinery worked by steam power. A flat stick is used by the grinder to keep the blade pressed to the surface of the stone. The ground blades are then glazed, which simply means that a higher degree of lustre and smoothness is given them by grinding on a tool termed a glazer. ”

“ If you have a stone with a crank arrangement, it will be necessary to have some one turn it while you control the tool. The stone should be turned toward the grinder and the tools held upward so the stone grinds against the edge instead of from it. Move the tools sideways across the stone so as to wear it down evenly and help prevent [Pg 38] the formation of ridges in the stone, which are very easily produced.
Fig. 34.—Grinding the Chisel. ”

“ They cut the stone into cubical blocks, and throw them into troughs, into which is poured a stream of running water. The blocks are kept in motion, and the grinding makes each block help the rest to grind off the eight corners and the twelve ridges of each one. The water becomes muddy with the fine particles, just as the drip from a grindstone becomes unclean when an axe is ground. Pretty soon all the blocks in the trough are changed into globes—the marbles that children buy at the shops when marble season comes around. ”

“ The face of a grindstone should be rounded slightly, and it should be kept so by grinding the tools first on one side of edge of the stone, then on the other, with the cutting edge of the tool crosswise to the face of the stone. ”

“ It seems almost demonstrable that some at least of these unpolished celts must be among the earliest of the Neolithic implements of this country; for though, in Neolithic times, some naturally-shaped stones have been sharpened for use by grinding only, yet the art of chipping stone into shape must in all probability have preceded that of grinding or polishing its edges. So far as at present ascertained, the practice of sharpening stone tools on the grindstone was unknown in Palæolithic times ”

“ In the barrow at Cowlam, already mentioned, besides the grinding-stones of grit, there was a piece of flint roughly chipped into a cubical form, and having one face partly ground smooth. It may have been used for polishing the surfaces of other stone implements, or possibly merely as a muller. It is shown in Fig. 184. The striæ run diagonally of the square face.
In the collection formed by Canon Greenwell, is also a sandstone pebble, 21/2 inches in diameter, which has been "picked" into shape, and has one face smooth as if used for grinding. ”

“ It is true that the Old Stone Age did not yet employ frictional processes in shaping stone and confined itself to the older methods of fracturing by blows or pressure. But the converse is not true, that the Neolithic worked stone only by grinding, nor even that grinding was its characteristic process. Stone grinding was invented only toward the middle of the New Stone Age—in what is perhaps best designated the “Full Neolithic.” The Early Neolithic, which lasted half the total Neolithic duration, continued to work stone by fracture. ”

“ The process of grinding large surfaces is entirely distinct from that of small ones, because of the difficulty in the former of getting rid of the cuttings. As an illustration of this point it may be remarked that a stone that has become dulled and glazed from operating upon a broad area of surface, as say a large plate, may be both cleaned of the cuttings and sharpened by grinding upon it a roller of, say, 1 or 11⁄4 inches in diameter. ”

“ Steel-grinding is divided into the dry, wet, and mixed methods; and the injurious effects vary according to the amount of water used on the stone. Forks, needles, etc., are ground on the dry stone, and accordingly the men and boys employed at this kind of work are found to be the greatest sufferers. ”

“ 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. ”

“ Grindstones, Emery and Grinding Wheels.—A good workman is always reflected by his grinding apparatus. This is true whether it has reference to a grindstone, emery, corundum wheel, or a plain oil stone. Nothing is more destructive of good tools than a grooved, uneven, or wabbly stone. It is only little less than a crime for a workman to hold a tool on a revolving stone at one spot. ”

“ A first-class ax, a real chisel, or a mortar in which grinding can be done, can [145] scarcely be made by chipping alone. It was not until men had learned to restrain their childish impulse to work only for the immediate purpose, and had acquired an increased self-control and discipline, that the grinding of stone came into use.
One principle must be clearly adhered to in the dating or proper arrangement of the periods of prehistoric time: the principle that it is always the highest types of implements which determine the age of a deposit. ”

“ Fig. 19.
These remarks apply to all chisels, plane bits and tools of that character, but it is obvious that a drawknife, which is always held by the handles in grinding, and hatchets, axes and the like, cannot be held in the same manner.
A too common error is to press the tool too hard on the stone. This is wrong. Do not try to force the grinding.
Then, again, it is the practice of some to turn the stone away from the tool. The stone should always move toward the tool, so as to prevent forming a feather edge. ”

“ So far as we at present know, not a single implement from the River-drift has been sharpened by grinding or polishing, though, of course, it would be unsafe to affirm that such a process was unknown at the time when they were in use. With the unpolished implements of the Neolithic Period, which most nearly approach those of the Palæolithic in form, it will as a rule be found that the former are intended for cutting at the broader end, and the latter at the narrower or more pointed end. Even in the character of the chipping, a practised observer will, in most instances, discern a difference. ”

“ Before proceeding to the consideration of other forms of implements, it will be well to say a few words with regard to those which have served for grinding, polishing, or sharpening tools and weapons, and more especially such as there is every reason to suppose, were employed to give an edge or finish to other materials than metal, though the whetstones of the Bronze Period must not be passed by unnoticed. ”

“ In the first place, within the limits of the Stone Age itself, an unmistakable upward development in the course of ages is to be discerned, in the traces of an early period when stone implements were only used in their rude chipped state, and were never ground or polished, followed by a later period when grinding came to be applied to improve such stone instruments as required it. ”

“ It is, however, probable that in the fashioning of perforated axes and other implements, made of greenstone and other rocks not purely silicious, some scraping as well as grinding tools may have been employed, and possibly the wear of the edge of some of these tools may be due to such a cause. Even among the cave-dwellers of the Dordogne we find scrapers bearing similar marks of attrition, and we also know that flint flakes were used for scraping the hard hæmatitic iron ore, to produce the red pigment—the paint with which the men of those times seem to have adorned themselves. ”

“ Fig. 19.—Mildenhall. 1/2 So sharp is it, that I should almost doubt its ever having been intended to be ground or polished. That a sufficient edge for cutting purposes could be obtained by careful chipping with- out grinding, seems to be evinced by the fact that some stone celts, the whole body of which has been polished, are found with the edge merely chipped and not ground. ”

“ If the chipped celt is to be regarded as unfinished, it may be that the survivors, in burying it, together with the grinding and polishing stones, in company with the original occupant of the barrow, entertained a belief that in some future state of existence he might be at leisure to complete the process of polishing. ”

“ The grindstone should be kept true and liberally supplied with water; the straight face should not be ground away, nor indeed touched upon the stone, except to remove the burr which will sometimes turn over. The pressure with which the blade is held against the grindstone should be slight at and toward the finishing part of the grinding process, so as not to leave a long ragged burr on the end of the blade, as is sure to be the case if much pressure is applied, and it will occur to a slight extent even with the greatest of care. ”

“ In some places, as at Laugerie-haute, surface-chipping is found on the flint arrow-heads, and cup-shaped recesses have been worked in other hard stones than flint, though no other stones have been used for cutting purposes.
3. That in the Neolithic or Surface Stone Period of Western Europe, other materials besides flint were largely used for the manufacture of hatchets; grinding at the edge and on the surface was generally practised, and the art of flaking flint by pressure from the edge was probably known. The stone axes, at least in Britain, were rarely perforated. ”

“ Among the Kaffirs [86] and in West Africa the mill is of this character, the bed-stone being large and heavy, slightly hollowed on its upper surface; the muller, a large oval pebble which is used with a peculiar rocking and grinding motion. The corn (maize or millet) is often boiled before grinding. In Abyssinia [87] the bed-stone of gneiss or granite is about 2 feet in length and 14 inches in width. ”

“ The grinders furnish their grindstones and all their tools for making the knives; there is no dry grinding, such as used to fill the lungs of the grinders with deadly particles of steel and stone, and bring them to an early death; but sometimes a stone, which ordinarily lasts six months, will burst and drive the grinder through the roof. The blade-makers do their own forging and hammering, and it is from first to last apparently all hand-work. ”