PART IIEVERYDAY MACHINES

Fig. 73. Simple barometer

"This simply consists of a wide-mouthed glass bottle filled with ordinary drinking water up to the point indicated by the letter A (Fig. 73); in this is dipped an inverted glass flask, or an incandescent light bulb, the extremity of the neck being allowedto dip just below the surface of the water.

"The flask should be inverted quite empty during wet weather, and as long as the atmosphere remains in a stormy condition, no change in the water takes place; but immediately the weather becomes finer, the water will rise in the neck of the inverted flask, and, if a continuance of fine weather be probable, will rise to the point indicated by letter B.

"I have found this simple contrivance to give sure and early warning of the approach of rain, and I need hardly remark that the principle upon which this little weather glass acts is exactly similar to that of the ordinary mercury barometer, for the rise and fall of the water is due to the respective increase or decrease of atmospheric pressure.

"By dividing the neck A B into six or eight divisions, with the aid of a diamond or piece of flint, and then marking the lines so cut, with ink, an approximate graduation of degrees of pressure may easily be obtained.

"I show you a water barometer here, (Fig. 74) that is somewhat less hard to construct than the one I have already described, as the parts are easier to obtain.

Fig. 74. Barometer

"It consists of a bottle, containing water, inverted and suspended with its mouth in the jar of the same fluid. It is capable of roughly indicating atmospheric changes in a similar way to the mercurial barometer. When the atmosphere becomes denser, the greater pressure on the surface of the water in the jar causes it to rise in the bottle; while with a lesser density it falls. As with the mercurial barometer, temperature makes a slight difference, which, strictly speaking, should be allowed for; but, as the arrangement is of such a simple character, this may be ignored. Water, also, is more subject to evaporation than mercury, besides going stagnant, and will require occasional changing and replenishing.

"A barometer of a more scientific character, and more presentable, is, I think, within your range of skill, and it may be made as follows: Obtain a glass tube, closed at one end, about two feet ten inches long and three eighths of an inch thick, with a bore of about three sixteenth inch. A circular turned wood box, one and one half inches in diameter and one and one fourth inches deep, is required forthe cistern. Cut out the bottom and glue on instead a piece of leather, sagging loosely. Then cut the lid in two, and make an opening in the centre to receive the tube.

Fig. 75. Thermometer

"The mahogany base, shown in two halves by A and B (Fig. 75), is 3 feet 1 inch long, 33⁄4inches at its greatest width, 2 inches at its least width, and3⁄4inch thick. Make a groove down the centre to admit the tube, and cut an opening 2 inches square right through the wood at the round end. Glue at the back of this a circular piece of pine or cedar, 3 inches in diameter and1⁄2inch thick, and screw a semicircular piece of the same thickness at the other end, with a ring for hanging.

"Fill the tube by degrees with pure mercury, boiling each portion, as introduced, by holding the tube in a nearly horizontal position over a spirit lamp, taking care not to crack it by too sudden heating. Half fill the wooden cistern with mercury,and when the tube is full, place a finger over the end, carefully raise it to a vertical position, and lower the open end below the surface of the mercury in the cistern. While some one holds the tube, glue on the two halves of the box lid and seal up the opening round the tube with wax or cement. Then fasten the tube to the base with brass clips and screws, and secure the cistern from shifting by gluing in wedges of wood. A thumb screw, with washer, for regulating the height of the mercury, is fixed at the bottom; this presses on a cork washer glued to the leather of the cistern.

"A hollowed hardwood boss is screwed over the top end of the tube, and a hollowed circular turned boss of mahogany, C, is glued over the bottom. The ivory or cardboard scale D, is of inches and tenths, from twenty-six and one half inches to thirty-one inches, the distance being measured approximately from the surface of the mercury in the cistern. A vernier having a scale of eleven-tenths of an inch, divided into ten parts, works in a slot on the scale and should be attached as shown at D.

"Before screwing on the scale, fix its correct position by comparison with the standard barometer.It is usual to place a small thermometer on the other side.

"With regard to the thermometers, it would be quite out of place here to discuss them at length, or to offer you a scientific explanation of the principles governing their construction. I may say however, that, as the barometer is intended to measure the different degrees of density of the atmosphere, so the thermometer is designed to mark the changes in its temperature, with regard to heat and cold. The first thermometers, so far as we know, were made less than three hundred years ago, and water, spirits of wine, or alcohol, and oil were used to fill the bulbs, in the order given. It was the great Halley, of 'Halley's Comet' fame, who first made use of mercury or quicksilver in these instruments, because of its being highly susceptible to expansion and contraction, and capable of showing a more extensive scale of heat. It is owing to this quality of expansion and contraction that the degrees of heat and cold can be measured. If you put your thumb on the bulb, you will notice the quicksilver in the little tube gradually rise until it reaches the limit of the thumb's heat. Thermometers, in this and nearly all English-speaking countries, make use of the Fahrenheit scale, which is differentfrom those used in some other places; and this often causes trouble and annoyance.

"The scale of Reamur prevails in Germany. He divides the space between the freezing and boiling points into 80 degrees. France uses that of Celsius, who graduated his scale on the decimal system. The most peculiar scale of all, however, is that of Fahrenheit, the renowned German physicist, who, in 1714 or 1715, composed his scale, having ascertained that water could be cooled under the freezing point without congealing. He, therefore, did not take the congealing point of water, which is uncertain, but composed a mixture of equal parts of snow and sal-ammoniac, about fourteen degrees R. This scale is preferable to both those of Reamur and Celsius, or, as it is called, Centigrade, because: (1) The regular temperature of the moderate zone moves within its two zeros and can, therefore, be written without + or -. (2) The scale is divided so finely that it is not necessary to use fractions whenever careful observations are to be made. These advantages, although questioned by some, have been considered so weighty that both Great Britain and America have retained this scale, while nations on the Continent of Europe use the other two. The conversion of any one of these scalesinto another is very simple. (1) To change a Fahrenheit temperature into the same given by the Centigrade scale, subtract 32 degrees from Fahrenheit's degrees and multiply the remainder by5⁄9. The product will be the temperature in Centigrade degree. (2) To change from Fahrenheit to Reamur's scale, subtract 32 degrees from Fahrenheit's degrees and multiply the remainder by4⁄9. The product will be the temperature in Reamur's degrees. (3) To change a temperature given by the Centigrade scale into the same given by Fahrenheit, multiply the Centigrade degrees by9⁄5and add 32 degrees to the product. The sum will be the temperature by Fahrenheit's scale. (4) To change from Reamur's to Fahrenheit's scale, multiply the degree on Reamur's scale by9⁄4and add 32 degrees to the product. The sum will be the temperature by Fahrenheit's scale. A handy table can easily be figured out from the data given."

Mr. Gregg concluded his conversation for the night at this point, but promised to take it up again the first available evening.

Two or three nights afterward it was very wet and dreary. The boys and Jessie were called into the den by Mr. Gregg, where a brisk fire, made oflimbs and branches gathered by the boys, was burning in the little fireplace, and the room looked bright and cheerful. The young folks all drew up around the fire to listen.

"I have so many things to talk to you about," said he, "that I scarcely know where to begin; however, I promised to tell you something concerning springs, so I will make these useful contrivances my theme to-night."

Fig. 76. Car-spring

"There are many kinds of springs, but I will only talk of steel or other metal springs; and even then must limit myself to a few. The carriage or laminated spring is probably the most in use, as it is an important factor in the construction of all classes of railway trucks and carriages, locomotives, automobiles, road carriages and light wagons of all kinds. These are also much used in the manufacture of invalids' chairs, children's perambulators, and many other things. The springs used in the construction of the largest locomotives are big affairs and often weigh over 500 pounds. These are bearing springs and carry the whole weight of engine and boiler. There are, of course, a number of these springs to each engine. Springs on the coaches and carriages are somewhat lighter and more flexible than those on the heavier trucks.The double spring, shown atFig. 76, is known in railroad parlance as a 'draw-spring.' One of these is secured at each end of the car, and used to attach or couple the cars together, or to attach the engine to the train, the object being to lessen the bump or impact of the blow when the engine and cars come together. The effect is the same when the engine starts a train; the springs in the first car draw out, then the springs on the second car do likewise, and this causes the load of the whole train to fall on the engine gradually, a matter of great importance in railway economy. If it were not for bearing springs on the trucks and carriages, it would be almost impossible to use railroads for passenger traffic or for carrying fine goods, as the jolting and pounding on the iron rails would shake things to pieces, destroy the carriages, and pound the roadbed and bridges to bits in a very short time. Now, by the aid of steel springs, you ride in a Pullman as smoothly almost asin a boat, so you see how useful springs are to mankind.

Fig. 77. Cross-bow spring

"There are many kinds of bearing springs, but all are built in the same manner, of steel leaves, made of different dimensions to suit conditions. As you will see in the diagram, the sheets of steel are laid over each other, like the scales of a fish, and made shorter as they approach the top. All the leaves are fastened together by having an iron buckle driven onto the middle, as shown, while hot, and when this cools, it shrinks and clasps the whole so tight it cannot be taken off until heated or cut. I could tell you of many other kinds of springs—watch springs, gun springs, trap springs, spiral springs—used for various purposes, but I will end this subject by describing to you something you can make for yourself, if you wish; namely, a cross-bow, which is very simple. I make on the blackboard a diagram, (Fig. 77), with A representing the stock, 5 feet long; B, the bender, 6 feet long, which should be made in four pieces. The front piece should be3⁄4inch thick, the three inner pieces1⁄2inch thick. C are brass ferrules to keep the leaves of the bender from shifting; D the string, which should be very strong. The bender should be cut out of straight well-seasonedash, rock elm, or hickory. Instead of brass ferrules, strong brass or copper wire can be used, properly twisted at the joints.

Fig. 78. Gyroscope

"The gyroscope has become quite famous of late, because of its having been employed as a steadier for the monorail car, and proposed as a regulator or governor for aeroplanes, so that I think it will not be amiss to tell you that a study of this toy is well worth any time and labour you may spend on it. There are great possibilities within this little instrument and its applications. I do not intend dealing with its principles, or with rotation problems generally, as they would, I fear, be beyond your present comprehension, but I will confine myself to describing the toy and showing you how it can be made, though it would be much cheaper to buy one from a dealer. The instrument consists of a ring of brass or other metal, like a curtain ring,and a smaller brass ring attached to a thick disc of white metal, or a metal disc with a thickened rim, as shown inFig. 78. This disc is securely fixed to a metal pin, which is passed through two holes in the outer brass ring, and at one side a small rounded nut or ball of brass is screwed on the outer ring. The metal disc is at right angles to the outer ring. If a cord is wound several times round the metal pin, the outer ring held in the left hand, the pin and metal disc will revolve at a very high speed, while the outer ring remains stationary. The gyroscope can be placed on the knob, and while the disc is revolving the outer ring can be placed at any angle, and will remain stationary. It is also possible to balance it at any angle on the top of a support, such as the tip of a stick."

Someof our inventions and some of our discoveries are of comparatively recent date, but most of them had their beginnings centuries before historical times, as many of our greatest inventions are the result of gradual growth and development. The early discovery, by some unknown persons or persons, of the making of bronze and the hardening of it, led up to stone and woodcutting, perhaps to the breaking-up and smelting of iron ore, and the extraction of the metals. This again opened the way for the making of steel, a discovery that placed in the hands of man a source of power which enabled him to overcome many natural difficulties. One improvement led the way to another, and made other improvements possible. Take locomotives and steamboats for instance. The making of a raft, no doubt, suggested the canoe, and this led to the built-up boat, and the ship. The paddle and the oar doubtless led up to the sidewheeler,and the scull to the propeller. The crude steam engine of Hero very likely suggested the steam engines now in use, and this new power rendered it easy for Stephenson and Fulton to perform their work; but, if either of these inventors were to come back to the earth and examine the great steamers of to-day, or the perfect and powerful locomotives now in use, they would be surprised to think that the present tractable monsters, were the outgrowth of their early efforts.

In the same manner may be traced the same gradual growth in all the arts and sciences; for step by step, in every department of life, have completeness and perfection come to us. It is not yet one hundred years since Congreve invented or rather completed the invention of the "Parlor match," called in his day, the "Lucifer match." This grand achievement was accomplished after many failures in the efforts of chemists for ages. The perfection of the match was a great blessing to humanity, as the old methods of making a light or fire were tiresome and very uncertain. So it is with many of the blessings we enjoy to-day: they are simply the results of the struggles of many unknown minds, the threads of which were gathered up and pieced together byone master mind, so as to be made useful and profitable to mankind.

In the early and middle ages, the inventor was looked upon as a wizard, a sort of inferior demon, or, at best, an uncanny kind of man, and a proper subject for the stake. When, by superior wisdom and skill, he invented some machine or device, or discovered some new and better method of accomplishing a useful end, he was at once looked upon as a necromancer in league with his Satanic majesty, and, therefore, unfit to associate with or be recognized as a Christian. History records many instances of inventors and progressive men being persecuted—and executed—because of their having discovered or invented something which would interfere with some vested or imaginary rights. The new inventions must be destroyed or put away out of sight and hearing, and the most powerful influences were employed to bring about this result. The stories told of Friar Bacon, Papin, Crompton, and hundreds of other inventors, give us a few of the reasons why so little progress was made in the arts and sciences previous to the sixteenth century.

Down to a period within the past few years the term invention has been considered almost synonymous with the word chance. An inventor, was alucky individual, who had happened to hit upon some new idea, not so much by his own great ability as by good fortune, similar to that which brings success to the purchaser of a lottery ticket.

In many cases this was really the true state of affairs. Men who experimented in various mechanical pursuits often stumbled upon results, which they perceived to be useful and valuable, and, if they protected the invention by patent, they often became wealthy.

At the present time this meaning of the word invention must be greatly modified, if not altogether abandoned. The law which controls the action of the forces of nature is becoming so well understood among all classes of mechanics that chance invention, in the early sense of the term, has almost become an impossibility. Success can be assured only to the man who has tried to win it by the acquirement of the necessary knowledge, to be obtained by steady application and hard study. In the pursuit of discovery, the old saying, "knowledge is power," never has had more force than when applied to unravelling the tangled web of nature's mysteries. "Science," says Lord Brougham, "is knowledge reduced to a system."

A man may have a lifetime of practical experienceand amass a fund of knowledge of great use to himself, but entirely unavailable for others. But if his experience be combined with that of other men and systematized into a regular order, it becomes part of the science of that branch of industry, and although the person himself may have a profound contempt for science and theory his work may be quite scientific.

Ignorance, in the past centuries, was another great factor in preventing mechanical progress. New machines and labour-saving devices were looked upon by the great mass of workers as contrivances designed to deprive them of the means of making an honest livelihood, and this point of view caused the people to smash and burn many machines that had cost great labour and expense to the unfortunate inventor. But, as public schools became more numerous and learning increased, the way of the inventor became smoother. The more enlightened nations encouraged inventors and inventions, and now our country has on its statute books laws for this purpose, the most liberal in the world.

The opportunities for obtaining mechanical and scientific knowledge and technical instruction are now so many and so easy of access that inventors have but little trouble in acquiring the data andfacts essential to their purposes. The earliest students had nothing but their own observations and experiences to build on, and even as late as the eighteenth century, men had to grope in the dark for the data required to carry out their ideas. A brief examination of the early treatises on mechanics and the rude illustrations in the works of Leopold, Amoutons, and Desaguliers will reveal the germs of many modern machines.

The inventor of to-day, however, must proceed by a different path from his predecessor, if he expects to succeed in the present advanced state of mechanical arts. The demonstration of the mechanical equivalent of heat, the discovery of the correlation of the physical forces, and the development of the sciences of thermo-dynamics have furnished powerful weapons for the advancement of mechanical science, and he who does not use them is at a woeful disadvantage in the fight. There is no "royal road" to success for the inventor, and I hope you will always bear this in mind when attending to your studies, for you must remember that it is nearly always necessary to use formulæ and symbols to express relations, which are hardly within the range of words, and often a combinationof data obtained from different sources may be used to derive entirely new relations.

It is here that invention, in the modern sense of the term, comes in to hold a place midway between theory and practice, and may be properly called a science.

Suppose a one-pound weight is suspended by a string: there is a tensile stress in the string, varying slightly at different parts of the earth, but always the same at the same place, say, Newark, for the variation is very slight within a pretty wide area. If we take a spring balance and graduate it in pounds at Newark, such a balance will accurately indicate forces in pounds wherever it may be used. The stress produced in a string carrying a one-pound weight at Newark is the unit of force. If the string with its weight is hung from a nail, the nail is pressed on its upper side with a force of one pound. The same pressure may be produced by pushing the nail downwards from above, using a short piece of stick; in such circumstances, the stick bears a compression stress of one pound. This is a good, common-sense definition of force, though it does not by any means cover the whole subject. The word force is used in a different sense by personswho speak of the force of gravity. When a one-pound weight is suspended by a string, as stated in the foregoing, the attraction between the mass of the weight and the mass of the earth is balanced by the stress in the string. We can double the stress by doubling the weight, and in this way, by adding weights, we can make the force of gravity very great. But the force of gravity is spoken of as an invariable thing, and it is said to be equal to 32 (roughly). If any weight whatever be allowed to fall freely (for reasonable heights and neglecting the effect of the resistance of the air) it will be found that at the end of the first second it will have a velocity of 32 feet per second; at the end of the second second it will have a velocity of 64 feet per second; and generally at the end of any number of seconds its velocity will be 32, and the rate of increase of velocity (acceleration) is 32 feet per second, all of which has been previously explained. It is found convenient to call this acceleration gravity—it is inaccurately called the force of gravity, it varies at different places on the earth. It is usual to designate the acceleration by the letter g, and we speak of the g, or gravity, of the place. This seems to cover the point of inquiry completely.

The subject of specific gravity is a far-reaching one, and includes the testing of liquors for revenue purposes and many other things of a scientific nature; but when we speak of specific gravity in an ordinary way we mean the comparative weight, bulk for bulk, of water at a certain temperature. The specific gravity of a substance like coal can be ascertained experimentally. By means of a specially adapted and delicate balance, the sample of coal is first weighed in the ordinary way, after which it must be weighed suspended in a vessel of water. Weighed in water, it will be found the coal does not weigh so much. If the loss of weight, or the difference between the first and second weighings be taken, and the first weighing divided by this loss of weight, we obtain the specific gravity of coal. For example, suppose a sample of coal weighs in the ordinary way 20 ounces, and in the water only four ounces, showing a loss of weight of 16 ounces. Divide 20 by 16, and we get the specific gravity of the sample of coal, viz., 1.25.

The use of specific gravity is of great importance in mining, with regard to analysis of the minerals worked, for with a class of coal having the same relative composition, qualities, and calorific power per ton of coal employed for different purposes,yet having a higher specific gravity, the room required for storage or transport will be less. This is an important factor, where there is limited space, as in depots and naval vessels. It is also employed in the arts and industries for many purposes, and is particularly useful to workers in precious metals, as the amount of alloy or baser metal may be determined by it that have been used in the manufacture of jewellery, plate, and similar articles.

To put it briefly: Specific gravity is the ratio of the heaviness of any substance to that of water. The specific gravity of water is taken as unity, and that of any other substance is expressed as a decimal. Tables of the weight and specific gravity of substances can be found in any good hand-book of engineering.

Sewing machines often get out of order, and it is not always that an expert is at hand to adjust them, so a few general observations on the subject of these household machines may prove useful and interesting to every one who is at all mechanically inclined.

There are several distinct types of machines, but we shall confine our remarks to the Singer vibratingshuttle, the hook shuttle types, and one or two others. To secure a perfect stitch in the vibrating shuttle machine, and to keep it from puckering thin goods, such as Japanese silks, muslins, and voiles, though possible, is difficult. Success depends entirely on the careful fitting of parts and the skilful adjustment of the machine to the particular fabric. In the first place, it is essential that a machine should work quite freely, a point not of such great importance if it is used for rougher classes of work.

Machines used for domestic purposes, like the V. S. (vibrating shuttle), often stand unused for weeks together, so that the oil thickens and makes a machine run somewhat heavily and unevenly. This may indirectly affect the regularity of the tension, especially with thin goods. Therefore, it is important to keep a machine clean and regularly oiled. Important parts are often overlooked during the operation; in fact, many users of machines do not know how nor where to oil one properly. Therefore Figs.79and80will be helpful, as they show the location of oil holes and parts to be oiled, and the illustrations will serve as a guide to other machines. In these figures, it will be seen that there are a number of parts to oil which could very easily be overlooked. When a machine has been unworkedfor a length of time, the application of a little paraffin will cleanse the parts which should afterwards be oiled thoroughly with a good quality of machine oil. The shuttle raceway, where the shuttle works, should be wiped out with an oily rag. Any lint or dirt which has accumulated inside the shuttle at the nose end should be withdrawn, as such might retard the unwinding of the bobbin. It is imperative that the cotton should pull evenly, that is, free from jerks; this refers to the upper as well as to the lower tension.

Fig. 79. Section showing oil holes

For silk and similar materials, best results can be obtained if fine cottons are used. Numbers 60, 70, or 80 would be preferable to No. 40. A good quality of fine silk is even better. It must be remembered that when working on thin silk, say twothicknesses, a coarse cotton cannot be locked centrally. Fine cotton will need a fine needle, which necessitates a fine hole needle plate.

Fig. 80. Action of shuttle in the race

If, after the foregoing points have been attended to, the machine runs easily, the parts fit properly, there is no end play to the upper shaft and the cottons pull evenly, yet the tensions are erratic, attention should be given to the loop as it draws off the shuttle heel. In machines of the C. B., O. S., and especially the V. S. class, there is a tendency for the loop to hang on the heel of the carrier, or to become trapped between the shuttle and the carrier heel. In the two former types of machines, the heel of the carrier should be rounded so as to induce the cotton to pass off as freely as possible. Sometimes it is necessary to time the shuttle a little later, that is, put the carrier back a little to allow the loopto draw off more in a line with the hole in the needle plate.

In V. S. machines the carrier is already rounded off at the heel. By referring toFig. 80, the action of the shuttle in the raceway can be seen, which is from A to B. The shuttle, having just entered the loop, is about to move to B. This movement can be regulated by an eccentric screw and nut (Fig. 80). When a machine has been taken to pieces and cleaned, this screw is not always replaced to the best advantage. If the shuttle moves too much toward B, the loop is carried by the heel of the carrier, and, at the same time, the shuttle cotton, by bearing tightly on the needle plate, pulls the shuttle toward the carrier heel, thus making it difficult for the loop to release itself. More tension is applied, perhaps more pressure is put on the take-up spring, yet the uneven tension is not overcome, and owing to the softness of the fabric, it is drawn up or puckered. The remedy is to turn the screw C (Fig. 80), until the carrier is in a position to allow the loop a free exit.

For such soft materials as mentioned it may be necessary to slacken both tensions. It should be remembered that the upper tension is generally somewhat tighter than the under one, and thisshould be a guide to the adjustment of the latter, according to the fabrics to be stitched.

To prevent puckering when the tensions are correct, reduce the pressure of the foot by loosening the thumbscrew D (Fig. 79). Use a small size stitch—set the feed so that the teeth are just above the needle plate. Do not have the teeth too sharp, and if necessary, rub off the knife edge with F emery-cloth. Make the foot to bear squarely on the needle plate, and the feed square to the presser foot. Round off all sharp edges from the under side of the foot, especially the back edge. Special feeders are made for silk goods in machines used for factory work, which overcome the difficulty of puckering.

By attention to the foregoing instructions, a machine should work easily, especially if the fabric is slightly pulled from behind the pressure foot.

In C. B. machines, attention should also be given to the loop as it passes over the bobbin case and off the stop pin, it being necessary sometimes to round off the latter. If the tension spring screw projects too high or is rough, it may occasionally catch the cotton.

The machine shown atFig. 81is of the "Rotary Hook"—zigzag type. Its uses are similar tothat of the oscillating shuttle type, but its construction is rather more complicated.

Fig. 81. Rotary hook—Zigzag type

Fig. 82. Rocking frame

The machine may be said to consist chiefly of an upper and a lower shaft, each having two cranks. In the vertical portion of the arm are two links which connect the shafts, causing them to work in unison with each other. The upper shaft gives motion by means of a cam and link to the needle bar and take-up lever; while the lower shaft, by means of three gear wheels, gives the rotary movement to the hook or shuttle, and by an eccentric cam and segment lever the necessary motion isgiven to the feed or stitch mechanism.Figure 82shows the rocking frame into which the needle bar is fitted at A and B, while, at C and D, it is recessed to receive the taper ends of two screws, which pass through the face plate end of the machine arm. These screws are held secure by lock nuts, so screwed in as to allow the frame to rock freely. A ball-headed screw is fitted at E, to which is fastened a connection rod extending to a switch lever situated about the centre of the arm. This lever, by means of a cam movement, gives the vibrating motion to the needle bar, which can be regulated according to the relative position of the connection rod and lever. When the rod is at the bottom of the lever, a wide throw is obtained. By raising the rod a narrower throw is given, and if raised to the position shown inFig. 81no vibration will be given to the needle bar. The needle bar can be raised or lowered by loosening the screw that secures it to its link collar, which will be better seen by removing the face plate. Most needle bars have two marks upon them, and they should be set as follows: Remove the face plate, and turn thehand wheel F (Fig. 81) toward you until the needle bar link has reached its lowest point of travel.

Loosen the set screw of the needle bar collar, and set the needle bar so that its highest mark will be just level with the bottom of the rocking frame (Fig. 82). Then tighten the set screw, give the hand wheel a spin round, and again examine the position of the mark when the needle bar has reached its lowest point of travel, to make sure that no mistake has been made. Of course, it is necessary when parts are badly worn to set the needle bar a trifle lower, but this can be done after the foregoing rule has been adopted and proved a failure. In case of any unnecessary looseness in the middle bar or any of its connecting parts, they should be taken out and new parts fitted. The position of the needle may be altered to the right or left by loosening the screws G and H (Fig. 81), and adjusting the connection rod. Care should be taken not to set the connection rod too low down, or the needle may strike on the needle plate and cause trouble.

Fig. 83. Section showing face plate removed from machine

Fig. 83shows the face plate removed from the machine arm, A being a tension release lever. When the presser foot is lifted to its highest position,the end of the lever goes between the tension disc, thus releasing all tension, so that materials can be taken from the machine without drawing slack cotton, or putting any unnecessary strain on the needle. When the presser foot is lowered, this lever should withdraw itself from the disc, thus allowing the proper tension to be put on the cotton. In some machines the withdrawal of this lever depends on a stud screw, fastened to the needle bar and projecting through the face plate. In the downward course of the needle bar this stud screw touches a spring, and causes the lever to trip backward. Should the spring become strained, or the stud screw become raised up a little, the release lever may remain between the disc and cause trouble. Sometimes it is necessary to bend the lever forward or backward to ensure its proper action.

Fig. 84. Hook ring

Fig. 85. Hook guide

Fig. 86. Hook driver

The hook or shuttle is rotary in motion. The hook (Fig. 84), is fitted to a ring, which is fixed to the hook guide (Fig. 85) by means of three small pins, and it is prevented from falling out by a steel cap secured with two screws and springs. Thehook is carried round by a driver (Fig. 86). Much depends on the hook, driver, and hook guide, so that a little detailed information is necessary. The hook driver must be a perfect fit in its bearings and free from sharp places where it comes in contact with the hook. The body of this driver is generally hardened, but the prong J (Fig. 86) is left soft so that it can be bent to meet requirements. When a machine is stitching, the hook driver rotates, and the prong J draws a given amount of slack cotton from the bobbin case. The farther this prong stands out, the more slack cotton it draws off the bobbin. The prong may be bent inward, as shown by the dotted lines, but care must be taken not to drive it in so far as to allow the needle when descending, to strike on it, or to deviate from its true vertical position. Points K and L fit between the nose and neck of the hook, while M comes against the heel. The hook is driven alternately by points K and M.When the hook is just entering the loop formed by the needle, it (the hook) is being driven by the driver wheel or M, and an opening is being made between point K and the hook nose for the free passage of the cotton. When the loop is being drawn off the hook by the take-up lever, the hook is driven by point K, and an opening is made between M and the heel of the hook for the exit of the cotton. There must always be sufficient clearance at points K, L, and M for the cotton or thread being used. As the heel of the driver M wears, the space at K will be reduced. Sometimes this can be remedied by bending the driver in at M, by giving it a blow with a hammer, placing a brass punch at M, but this should not be attempted if the driver is very hard. There is a means of adjustment provided in the hook guide (Fig. 85). This part is held in position by two set screws N and O. At the left of O is a small adjusting screw P. Supposing there is not sufficient space at point K (Fig. 86), for the cotton to pass, loosen the screw O (Fig. 85), and slightly tighten the screw P. This will tilt the hook guide and give more space. Should the screw P be turned in too far, the point L (Fig. 86), will be brought in contact with the narrow part of the hook near the neck, and this will impedeits freedom, so that if allowed to run at much speed, the probable result will be the breaking of the hook off at the neck. This should be noticed in fitting a new hook, as the adjusting screw P (Fig. 85) will in all probability require loosening. The screws at N and O, however, must be kept quite tight. At each side of N is a small screw hole. The screws which fit here are for adjusting the hook closer to or farther from the needle. As an example, supposing a very fine needle has been used in the machine, and it is now required to take a very coarse one on account of the thick material to be stitched, the hook in all probability would strike the needle, indicating that the hook guide requires moving back a little. To do this, loosen the two small adjusting screws and tighten the set screw in N. Afterward try the set screw in O to ascertain if it is secure. In this way, the hook is thrown farther from the needle. Loosening the screw at N, and tightening the adjusting screws, will bring the hook forward. If the hook stands too far from the needle, it is likely to miss the loop. The hook nose must be well pointed and perfectly smooth, roughness or sharpness removed from any part of the hook over which the cotton passes during the formation of a stitch.

Hook rings are made in three sizes, numbers 1, 2, and 3. Number 1 is for a new hook, numbers 2 and 3 are for fitting as the hook wears. No matter what size of ring is used the hook must have perfect freedom. Sometimes the three pins in the guide draw the ring, and cause the hook to bind. It is best, therefore, to fix the ring to the guide, and then test the hook. If it is at all tight, grind it on the rim by means of an emery wheel or a grindstone. If neither is available, use number 1 or number 11⁄2emery cloth first, finishing with number 00 emery cloth. It is better to have the hook a little loose, even sluggish, than too tight. The timing of the hook will be dealt with later on.

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