Modern Milling, by Robert Gimshaw, 1881
The following extempore addresses were delivered at the solicitation of Eastern millers and others, and with the intention to outline in clear and popular form, the changes that are taking place in the great and growing flouring industry, to which this country already owes so much. They are here published from Phonographic reports, substantially as delivered; merely excising some repetitions and purely local or ephemeral remarks, and adding a few foot notes, &c. They seemed appreciated at the time of their delivery, and it is to be hoped that they may interest and in some measure instruct many before whom the author had not the pleasure of appearing in person, on the occasions of their delivery. Philadelphia, June 1881.
I have chosen at the subject of my remarks "Modern Milling," rather than the title "New Process Milling," which has been advertised, - because "Modern Milling" covers a wider field than the works "New Process," which have often bee applied, but which are a misnomer. "New Process," as a trade term, is strictly a definition of one of the many new processes, or new systems, which constitute modern milling. (1) (1.) Just as to how many "processes" there are in modern milling, or where the dividing lines between them are, is by no means settled-some recognizing only two, others a dozen or more. The advance of milling, within the last decade, has been a great stride,- as great a stride as from the time when that prince of millwrights, Oliver Evans, lying upon his back and looking up at the dusty beams of the Brandywine Mills, studied out the elevator, the hopper boy, and the spiral conveyor; and almost as great a stride as from the early days of the quern, or rough stone, used for bruising the grain in the hands, up to Oliver Evans' date. (2) (2.) 1795 is the date of his book on milling. While there are many things in modern milling which were suggested or invented, or even actually practiced experimentally, hundreds of years ago, yet within the last ten years, and especially in America, the changes which have been wrought have completely revolutionized the business. These changes have bee radical and searching; there have been changes in the apparatus employed; in the mode of dressing and handing the apparatus; in the material converted, and in its preparation; in the process employed in converting the material; in the product of the new apparatus, materials and processes; in the location of the industry; in the customs of the trade; in the size of the mills; in the motive power employed in the transmission; in the market for the new products; in the importance of the industry - changes so radical, so complete, as to have transformed the old art or rule of thumb into a complicated but exact science, worthy of the most intelligent study of modern genius. While we may divide the art of milling into two great methods, high and low grinding, these changes which have taken place have so pervaded every operation in milling that there may be blocked out five or more separate systems or processes in the grinding or granulation alone; each of these following some changes and preceding others, so that the various processes so delicately shade off one into the other, that it is difficult to classify them. When we divide the art of milling into five or more processes we may divide them with reference more particularly to the mode of grinding or granulation, which is the principal operation in milling. Grinding or granulation may be effected by any one of four or more great classes of machinery. First, flat cylindrical millstones built up of blocks of buhr-stone- a hard, porous siliceous rock occurring in nodules in a very few quarries. These may have either the upper or under stone the runner; or may be set vertically. In any of these three cases either the runners or the bed, or both, may be either rigidly attached to the axis, or oscillating. The second class consists of rough or corrugated iron disks or cones. (3) (3.) Iron disk bids fair at present to develop into a formidable claimant for public recognition. The third, which has grown so rapidly in importance, includes rollers, which may be of biscuit (miscalled porcelain), stone, corrugated or smooth iron, or steel; and whatever the material employed for the rollers they may be used either singly, working against a concave, or in pairs; they may have motion either in the same or in different directions, and at either equal or differential speeds. The fourth class of granulating machinery includes those operating by percussion or attrition. (4) (4.) Not in practical operation in this country, unless perhaps in one or two small mills. A fifth class, perhaps only a variation of the first, and not yet in practical operation, consists of granulating disks composed of glass blocks or of porous blocks of biscuit ware, and intended to replace buhr-stone as a material for millstones. Cutting rolls also employed, as well as compressed air to blow the berries to powder. (5) (5.) More of a scientific to than a working success. Employing any one of these classes of machines or any combination of them, we may grind either "high" or "low," or by "gradual reduction" - that is, (1) we may aim to make as much flour as possible at one grinding from the wheat; (2) we may try to produce at one operation very small but sharp granular pieces of the berry which shall subsequently be ground into flour; or (3) we may endeavor to produce granular pieces with several gradual reductions, and to produce the highest grade and the greatest quantity of flour from these. The first system is called low milling, the second high milling, and the third, gradual reduction. (6) Of course so many subdivisions of such a complicated work could not be thoroughly or even superficially brought out in the course of two evenings' remarks. We shall then, confine ourselves more particularly to the consideration of two subdivisions. (1) High milling with buhr millstones; that is, buhr middlings milling; and (2) high milling with rollers; that is, roller middlings milling. (6.) Hardly any two authorities agree as to where the dividing lines exist. It shall be my endeavor to block out for you an outline of the many operations in each of these methods of milling, which in most respects (outside of granulation, in which they radically differ) lie parallel. I shall first rehearse in greater detail the changes which have taken place in milling, not merely since the day of Oliver Evans, but in the last ten years. First, in the material. Formerly the hard spring wheat which is the output of our north-western territories and cold climates was difficult to handle, not so much by reason of its hardness, as because of the extreme thinness and brittleness of its bran. Now, this hard spring wheat is by preference employed, not only because the new granulating devices handle it better than those of old, but because new machines have sprung up rendering the miller largely independent of any condition of the bran upon the berry. In order that we may more distinctly comprehend the operation through which the berry of wheat passes. When a section of a grain of wheat is magnified, you will note that its outer envelope consists of five layers, and these layers being thin, scaly, and fibrous, and constituting of woody envelope or bark, commonly called the bran; a material not only valueless to the miller, by extremely troublesome by reason of its tendency to mix with the more valuable portion and to remain there adulterating and diluting it. Within this outer coating of bran comes a layer containing the most valuable part of the berry, and which unfortunately lies next to and almost adhering to the worthless bran. This layer consists of cells of gluten a substance containing a higher percentage of nutriment than the rest of the berry, and giving to the flour its strength and its rising properties. The more gluten the flour contains, the "Stronger" it is; the better the dough can be made from a barrel of it; the better the dough will rise, and the more nourishing the bread will be. Within the layer of gluten lie the albuminous starch granules which constitute the greater bulk of the berry. The germ or embryo, a yellowish, oily body, not desirable as a constituent of the flour -largely by reason of its discoloring properties. The "fuzz" or beard of fine woody fibres; innutrious discoloring, and undesirable. Snugly tucked away in the crease of the berry, is a certain amount of bluish "crease dirt," difficult to remove, and extremely retentive if its place in the flour; and of course discoloring in its properties. The whole berry, and a few berries just cracked lengthwise, as by ideal milling, to liberate the germ. Lying upon and adhering to the outer coating of bran, as well as partly in the crease, there is a certain amount of loose dust, innutrious and discoloring. There is also in any large bulk of wheat a varying proportion of mechanically mixed impurities, such as oats, chaff, chess, cockle, sticks, stones, straws, garlic, grass seeds, sand, gravel, rat dirt, rivets, iron wire, miscellaneous fragments of metal, &c. In Pennsylvania and in neighboring sections there is great trouble from garlic seeds, which not only have a strong odor and spoil the flour, but contain a gummy substance which fills up the pores of the stone and glazes their faces, so that they have to be washed every few hours. Now, the great problem of the miller is to remove all the mechanical impurities, all the innutritious and discoloring portions of the berry, and to avail himself of the albuminous starch granules, and of the gluten cells, especially of the latter. It is not an easy problem to solve, and it should be a source of great wonder that its solution has been so satisfactory, not only from a technical point of view, but a commercial success. In the preparation of the wheat, the changes that have taken place lie in its much more thorough handling and cleaning, and in the toughening of the bran. The old operations are more thoroughly performed, and are supplemented by new ones. The object of cleaning is fourfold:- First.- To extract from the wheat as thoroughly as possible all the dust, dirt, clay, stones, and foreign substances' which would tend to impair the quality of the flour, together with the beard and crease dirt in the berry itself. Second.- To extract any light, shrivelled or soft berries that are among the sound ones. Third.- To remove any grass seed, garlic, cockle, oats, and other seeds, clean or otherwise, that it may contain. Fourth.- To insure that it is perfectly dry. Before grinding, the wheat, if it be all wet from having come in leaky canal boats, or from other such causes, is thoroughly dried to prepare it for the subsequent operations. It then passes through what is known as the separator, the object of which is to remove by sieves and by currents of air the lighter mechanically mixed impurities; the sticks, straw, chaff, chess, oats, &c. Good wheat should not have a half a pound of dirt to the bushel. It then passes through the "smutter" or "scourer." The object of this is to break up the smut-balls and to remove the less tightly adhering particles of dirt from the outer part of the berry. The smutter consists of an upright drum revolving in a case of perforated metal. Between this revolving drum and the perforated case the wheat falls; the rapidly revolving drum breaking up the smut-balls and effecting a thorough scouring of the wheat berries among and against the beaters and the walls of the perforated case. A current of air drawn in from below by the fan above carries this dirt through the perforations in the case into a surrounding jacket, and out of the building. It is desirable to effect as thorough a cleaning as possible without breaking the berries, after being graded in size. In some mills the fuzz or beard is removed by causing the grain to pass in a perpendicular position between large rotating sandstone disks called "ending stones." (7) (7.) There is hardly any one subject upon which millers differ so radically, and dispute so rabidly, as this one question of ending stones. I may say, however, that i do not know of any of our mammoth North-western mills that use them. While the scourer effects a most satifactory change for the better in the appearance of the berry, it does not remove all mechanically adhering dirt. That in the crease seems as yet indislodgeable (if there be such a word- and if there is not, I shall make it to order and use it while new). To attack this (the crease dirt, not the word) the brushing machine is employed. It is similar to the smutter, save that the drum consists of a cylindrical tampico brush revolving in close contact with the case. This brush gets at the crease dirt and largely removed it, besides which it polishes the bran coating, so that the once dull, lifeless wheat, intermixed with all kinds of filth and other impurities with a bright and smiling face. The cylinder is combined with a smutter and brush machine, removed from the case. Almost any cleaner that breaks wheat causes a waste. The wheat cleaning machine should be placed so that it can be easily reached and carefully looked after by the miller. (8) (8.) No general rule can be laid down as to where the cleaning machinery should be placed. this must be determined for each particular mill, according to the special conditions there existing. There is no use in saying that wheat can not be cleaned so that there shall be no fuzz on the end of the grain, because this not only can be done, but is done every day in many mills. The fact that it is not done in nine out of ten shows that there is room for improvement there. Among the changes that have taken place in the preparation of the grain may be mentioned one which is dependent upon or caused by the change in the mode of harvesting. With the introduction of the wire-binding reaper came a new trouble to millers; the presence, in the wheat, of sharply pointed bits of iron and steel wire which are liable to strike fire when they reach the buhrs, and thereby to cause an explosion and a fire, or if they do not do this they become flattened out and like tiny knives or saws cut themselves through the thin and expensive bolting silk used in covering the reels. To get rid of this nuisance the magnet was called into play. In the passage of the grain through spouts in which the poles of U-shaped magnets project, the iron and steel particles cling to the magnets and may be removed at intervals. Magnets are best put in spouts where currents of air work through the wheat. Curiously enough it has been found that the wire binder is not responsible for all the iron that the wheat contains, for the magnets are found to remove an assortment of particles of iron and steel quite enough to constitute a young junk-shop. (9) Among these may be mentioned rivets, fragments of iron, tacks and nails, bits of elevator cups, particles of iron ore, &c. (9.) Of course the magnets will not take out brass or copper wire, though some millers expect them to. These do not strike fire, but they cause trouble by cutting the bolting silks. The next thing in a well-regulated mill should be the grain meter-a device which not only weights the amount of grain used by the mill, but measures it flow. By this the miller may know on any one day or at any one hour just how many bushels of wheat it is then taking to make a barrel of flour, so that if he see on Monday that he is making a barrel from four bushels and thirty pounds of wheat, and on Friday that four bushels and fifty pounds are being used, he may search for where the waste is and rectify it. I told you that one of the principal troubles with which the miller had to contend was the extreme brittleness of the bran, which is more difficult to handle in some varieties of wheat than in others, and at some seasons than at others. To toughen this bran is desirable; to make the grinding and bolting even the year through he employs, if he is using millstones, a heater, the passage through which immediately precedes the entrance of the wheat into the eye of the millstone. In a Welch wheat heater the stream of wheat passes between steam heated metallic surfaces. The heat draws the moisture from the interior of the berry and effects the toughening of the bran. The wheat heater enables the miller to get a uniform grade of flour the whole year around. Hard, flinty, and dry wheat especially need heating, as their bran is always brittle. The skin is tough only so long as hot. In the Western and Southern States it was at one time recently customary to bring live steam in contact with the wheat, but this operation should be condemned, as there is more than sufficient moisture in the berry itself to accomplish the desired toughening. Heating is not so necessary where rolls are employed in granulating, as where buhr-stones are used; in fact, one trouble sometimes experienced is in the use of heaters for gradual roller reduction. It is that after the first break, and especially after the second break, it becomes pulverized even worse than if heaters were not used. But for buhr milling, to meet modern demands, it is now an absolute necessity. The next operation is grinding or granulation. In the buhr mill (or "stone" mill,) there are employed either upper runner stones, that is those in which the upper stone revolves, and the lower is the "bed" or stationary stone, or under runner mills, in which the upper stone is fixed and the under one rotates. Vertical stones are generally for portable mills. In my remarks I say nothing of grinding any other material than wheat (of course including in wheat milling the grinding of middlings and the cleaning of bran). Usually, when the upper stone is the runner, it oscilates upon a point on the top of the vertical spindle which drives it. The connection between the two is loose, so as to allow the stone to oscillate and adapt itself somewhat to any lack of horizontality of the bed-stone or any inclination or eccentricity of the spindle. One of the most improved drivers for transmitting motions from the rotating spindle to the bail or iron support is so constructed as to allow a large amount of oscillation and adaptation of the runner, without undue vibration, tremor, or fitfulness of running. This is called the Sergeant Driver. * * Note the Sergeant Driver, illustrated in Fig. 10, page 22 of this book, is a device that its existence possibly came and when with the publication of this book. Reference to its existence or usage may therefore be found only in this book. The oscillating upper runner is the oldest known. In the upper runner the pressure, and hence the fineness of grinding to a certain extant, are given by the weight of the runner; usually fifteen hundred to two thousand pounds. In the under runner the fineness of grinding is governed solely by the distance between the buhrs, which is regulated by a screw. Under runners can be driven faster than upper; they can use a smaller eye, and hence grind nearer the centre, and they choke less. An upper runner is easier to take up and down than an under runner; when down it is easier to adjust than an under runner; and when in motion it adjusts itself better to foreign bodies. When grinding there is less pressure on the step than with the under runner; the bush is less intricate and more durable, but the under runner has the greater capacity of the two. As regards the question of stiff or oscillating connection (rynd), it is very easy for any miller who has two run of buhrs to try the two side by side on the same work, and see which is the better. The changes which have taken place in buhr millstones employed in modern milling are, first in the material of their composition. This hard, porous, siliceous stone comes from a certain district in France, from the long opened and long quarries of La Fete-sous- Jouarre. The best of these are rapidly becoming exhausted from the drain upon them from all quarter of the civilized world, so that the old stock is becoming scarcer and higher priced, and is being replace by closer and harder "new stock" from new quarries, not so good for wheat. The clear white and sometimes variegated stone, resembling marble, is among the best for all uses, being free and hard, and holding an edge well; the yellowish is by most millers considered the worst, and has a tendency to glaze. Cream light and drab are among the best. A good millstone is told by its even grit, even texture, even opening, and even color; and best of all by its close resemblance to one solid piece of stone with the joints hardly distinguishable. The blocks should be joined the entire depth and not simply with a face joint. (10) (10.) These are very few mill furnisher able and honest enough to make and supply such buhrs. No matter what material be chosen, the stone should be built up of blocks of equal weight and porosity throughout and as far as possible of blocks of the same size in the same part of the stone. In the runner the block should be of the same size or thickness. The size of the millstones is being decreased. Whereas in the olden times stones of four and a half and even five feet in diameter were used, now four feet is the largest size employed, and three and a half feet is very usual in certain granulations. (11) (11.) Middlings stones are used as small as two and one-half feet; and many portable mills have vertical buhrs this small. We find under runners gradually replacing the upper, especially for grinding middlings. New Process buhr milling properly requires as many run of stone on middlings as on wheat. The "dress" of the stones, that is the mode of laying out and making the furrows, and grinding surfaces, has changed. Whereas the furrows used to constitute about one-third the area of the stone, and the "lands" or level spaces between them the other two-thirds; now it is the rule to put in as much furrow and as little land as possible, the proportion being now nearly two-thirds furrows to one-third land. Whereas the granulated surfaces were once carefully cracked or finely grooved by a skillful dresser with a pick; now smooth surfaces are more in vogue, as tending to tear the bran less. The dress of the millstones is a subject on which no two millers seem to coincide, except where they agree that each variety of material, each kind of milling, and each kind of stone require a particular dress. A dress that will suit 140 revolutions will not suit 175. There are over two hundred different kinds of dress in use, each having it advocates. (12) (12.) A special paper on Millstone Dressing, by the author, is in preparation. Whereas a heavy pick of finely tempered steel, handled by an expert workman, was formerly exclusively used in the tedious operations of reducing the grinding surface to a perfect plane, and making the furrows accurate in depth, width, slope, and surface- now the diamond dressing machine, which is really a planing machine with a diamond tool is largely used to effect the same operation in at least one-fifth of the time.* * Note the Coplin Emery Wheel Dresser, and the Deal's Corundum Polisher illustrated in Fig. 13 and 14, page 27 of this book, is a devices that there existence came and when with the publication of this book. Reference to its existence or usage may therefore be found only now as curiosities in milling and millstones books of today. They are tools of museums rather than of the millstone dresser. A rotation emery wheel is also less generally employed. The makers of emery wheel millstone dressers claim for their machines a smoother furrow and face, and a more distinct and sharp feather edge than by other modes of dress, thus making a free passa e between the stones and through the furrows. They claim that this adds to the quality of the flour and to the capacity of the stones thus dressed, and requires less wheat to make a barrel of flour. It is also claimed that the bran is less cut and pulverized, that there is less bran with the flour and less flour with the bran. As regards to the question of economy of labor, what two men would do in a week with picks one man with the dress would do in two or three days, thus saving three or four days' work of the stones to the owner of the mill and eight days' wages. These two classes of machines exist in great variety, and are rapidly coming into favor and use. By them, less skilled mechanics may effect better work than was formally done by the expert, and in one-fifth the time: besides which, the buhr is not idle so long. Blocks of emery or corundum are also used to sharpen the face and furrows. The driver was formerly a clumsy, expensive cast-iron affair, with plenty of lost motion; now it is scientifically designed, and reinforced by steel wearing points and with mathematical accuracy. The mode of feeding the buhr-stone was formerly by means of a shaking shoe and damsel, making what was then considered cheerful music, but which is now conceded to have been an awful row. Now a quite, adjustable "silent feed" pours its steady stream into the eye of the stone. Formerly there was trouble from the heating of the millstones, which caused killing or deadening of the flour, also from accumulation of moisture in the spouting, which caused clogging of the bolting silk, and dampness and sourness throughout the spouts. There was also great danger from fire and explosion caused by the extremely fine dust, which mixed with air in certain proportions, forms a highly inflammable and explosive mixture, and has wrecked many a mill. the introduction of the wire binder increases the risk in mill having no magnets. Now this is obviated by the millstone exhaust which by means of which a current of air is drawn with the feed through the eye of the stone, and keeps the chop or ground product cool and dry, the bolts free, and the passages sweet and devoid of putrefying matter; besides which it saves a certain amount of somewhat valuable material. The heating of the chop by frictional contact with the millstones is in some mills cured by means of a chop cooler. Now let up see what the problem is in buhr middlings milling, and how to solve it. In olden times the chop which issued from the millstone consisted (we will suppose well-cleaned wheat to be used), first, of a large percentage of flour, among which there were particles of bran; second, of middlings or imperfectly ground bits of berry, mostly consisting of the portion richest in gluten, lying next the bran. To these middlings, particles of bran and flour adhered. The third material was bran, to which particles of flour adhered. The aim of the miller was to make as much and as white flour, as large and as clean bran, and as few middlings, as possible, because these middlings, although the most valuable portion of the berry, were of little use to him except as feed, by reason of his inability to remove from them the particles of bran. Now-a-days the miller has had solved for him the difficulty of purifying the middlings from the particles of bran adhering to and mixed among them. Since the middlings purifier (which we shall consider in detail further on) has been introduced, the aim of the miller is to make as many middlings as possible, to make them as sharp and granular as he can, to separate the other products from them, and to grind them separately; under which treatment they yield the celebrated "patent flour," the whitest and strongest that can be made. The next problem of the miller is to get the flour and bran separately from the middlings, and to get the bran specks out of the flour. The latter task he generally accomplishes by means of a rotating reel, almost horizontal, covered with fine silk cloth, the meshes of which vary in size from the head to the foot of the reel. One of the most improved bolting chests, in which the reel and the screw conveyors rotate; another one uses the new principle, the bolting silk being on a stationary screen, and the chop being thrown against it. Throughout the meshes of the silk covering of the rotation reel the flour passes, the finest at one end and the coarsest at the other. No. 15 bolting cloth, now in common use, contains 21,904 meshes to the English square inch; No. 20 (not often used) contains 29,929. (13) (13.) There are few articles in which sophistication is so common as bolting silk. none but leading brands should be purchased, and these only of well-known and reliable houses. Of course a certain amount of bran specks pass through the coarsest meshes. Bran, besides darkening the flour, produces fermentation, making sugar and gum in the bread, hence giving it a dark color. What tails over is in this case of very little value, because we have supposed the large bran flakes to have been scalped out before. A bird in eating a grain of wheat always rejects the bran. To get the flour off the bran scales, they must be handled tenderly, because, if beaten or brushed thoroughly, the edges of the particles will chip off and discolor the bran flour. This bran flour may be removed, first, by passing the uncleaned bran between millstones and then bolting; second, by whipping or beating machines such as are employed for breaking up quartz ores; third, by large brushing machines of which are somewhat similar to those employed for effecting the final cleaning of the bran. The middlings are generally "dusted" or disintegrated" to remove the particles of adhering flour. They then pass through a machine called a purifier, which has done more to revolutionize milling than has any other class of machines in the mill. In the middlings purifier there are employed two modes of separation-sieving and air-flotation. (14) (14.) Frictional electricity is now being tried as a means of middlings purification. The reddish mass of unpurified middlings contains particles which differ in size, in shape, and in specific gravity. They are fed down a slightly inclined lengthwise shaking screen, covered with bolting silk of varying coarseness, the finest at the head. Through this screen, comes from below a current of air adjustable in quantity, direction, and velocity which passes through the thin layer of middlings lying upon and traveling down the screen, and lifts and floats off the offal or fine bran dust. The fine middlings passes through the fine meshes at the head, while the coarse purified middlings pass through those at the foot. Some material tail over to be rehandled, and the offal goes into the stive room. If the middlings purifier be well adapted to the work, the fine offal will contain very little fine flour, but will be perfectly valueless except for feed. In the purifier every provision is made to grade the currents of air to suit the materials handled, the aim of the miller being to produce middlings which are as hard and granular, and as little flaky as possible. Middlings require careful handling to avoid breaking them up. The miller must adapt the silk cloth and air current of the purifier to the material which he is handling Often purifiers are given uneven middlings to work on, and then blamed for poor work. Other things being equal, hard spring wheat and "new process" milling make larger and sharper middlings than soft winter wheat and "pld process," and require a closer colth and stronger air current in the purifier. Brownish middlings are heavier than white ones. The fibre in middlings is often so fine as to be made brown only by the red shade. Soft returns from rolls, tailings, and finished middlings are hard to purify. The changes in the bolts rendered necessary by the modern systems of milling are more silk surface and finer meshes, reels of less length and diameter, and an entire difference, which I can not explain in a mere general outline, in the operation of the reels and in the systems of bolting. The American and Hungarian millers use more silk bolting surface than the English. The spiral conveyors below the reels carry the material outward and along. By means of suitable cut-off slides, the miller can spout off separately the material that passes through any portion of the length of reel. There is this thing that can be said in favor of buhr-stones:- Nine out of ten that have been working during the last twenty years have been badly hung, ignorantly dressed, and wrongly run, and notwithstanding this, is capable of doing so mush and so good work as the stone has done, much better can be done in the future when people better understand it, and with increased demand for it, increases its range and capacity. The millstone must be given not only a perfect standing balance, but a perfect running balance, so that no portion of it shall tend to tip. The spindle must be well made and accurately set, and the bush or followers in which its upper end runs must be adjustable to suit any inclination or eccentricity. To secure perfectly steady, even motion, and freedom from the evils of backlash, which are caused by irregularity in gears, slipping of belts, and by the uneven action of the crank when stream is used as a motive power, it is best to have an "anit-backlash spring" upon the spindle. It is impossible to do sharp, cool, clean, and even grinding unless the stone be in perfect face. To produce a geometrically accurate face in a practical and simple manner by an instrument that is easily handled and applied, and will neither require truing nor premit of bad work being done with it, I have devised an improved traingular iron paint staff, which has the simplicity of the oridinary red staff, and the case of application of the wooden circle staff. It proves three narrow beds, as the miller always does with his straight red-stick,; but there is no possibliity of these beds being out of plane with one another. It reaches every inch of the burr face, always applying the inexorable "trangular proofs."
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