Chapter X: Part II: Everyday Machines (1)

I

SOME PRACTICAL ADVICE

Some of 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 by one 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 a lucky 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 experience and 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 and facts 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 combination of 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.

THE LAWS OF GRAVITATION

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 persons who 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.

HOW TO ADJUST SEWING MACHINES.

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 vibrating shuttle, 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. 79 and 80 will 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 unworked for 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.

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 two thicknesses, a coarse cotton cannot be locked centrally. Fine cotton will need a fine needle, which necessitates a fine hole needle plate.

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 loop to 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 to Fig. 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 this should 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 at Fig. 81 is of the "Rotary Hook"--zigzag type. Its uses are similar to that of the oscillating shuttle type, but its construction is rather more complicated.

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 is given to the feed or stitch mechanism. Figure 82 shows 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 in Fig. 81 no 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 the hand 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 shows 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.

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. The hook 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 impede its 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 1-1/2 emery 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.

The bobbin case (Fig. 87), fixes to a stud in the centre of the hook. It is held in position, that is, kept from revolving with the hook, by means of a stop pin, Q, fitting between a holder. The tension is obtained by a spring, R, which is regulated by turning a small screw, S, to the right to tighten and to the left to loosen. Fig. 88 shows the bobbin case in position, with the holder raised ready for taking it out of the machine. Fig. 89 shows the bobbin in position in the bobbin case and method of threading, and Fig. 91, the direction the cotton should draw off the bobbin when it is in the machine. It will be noticed that the cotton pulls in the opposite direction to which the hook travels, as shown by an arrow in Fig. 88. The bobbin case holder (Fig. 91), should prevent the bobbin case from revolving with the hook. As parts wear, the bobbin case is liable to slip past the holder, causing the cotton to be stranded and broken. When such is the case the holder should be bent as shown by (Fig. 92), but it must not fit so tightly against the bobbin case as to cause the cotton to become trapped. The holder is held rigid by means of a catch and spring T (Fig. 88). Should the catch or holder become worn, fit new parts by driving out the pins U and V. Any sharpness or roughness on the forked part of the holder should be removed. Should the stop pin Q (Fig. 87) become loose, it should be soldered and well cleaned with an emery cloth. The centre tube of the bobbin case should also be kept quite firm. Should it become loose, place it over some hard substance, rivet it until tight, and thoroughly smooth with very fine emery cloth.

The take-up spring (Fig. 93) is attached to the face plate, and is shown in position in Fig. 83. Replace a new one as follows: First take out the set screw W (Fig. 93), and remove the complete thread controller from the face plate. Then take out the screw and withdraw the old spring. Place the ring part of the new spring in the recess between plate Y and back plate Z, and replace the screw X, being careful not to get the spring fastened under the screw head. This done, fix the spring and other parts on the face plate. A small barrel with a slot in it receives the coiled portion of the spring. See that the part of the spring that is turned in enters the slot in the barrel, then replace the screw W, but before tightening this screw, see that the hooked part of the spring A´ rests on the regulator B´, which determines the amount of action given to the take-up spring. By raising it, less action is given. The amount of pressure on the spring is regulated by adjusting the barrel in the face plate. Take off the face plate, loosen the screw C (Fig. 83), fix a screw-driver in the rear of the barrel (seen inside the face plate), turn it toward you for more pressure, and backward for less and tighten the set screw C.

Presser feet are made solid for ordinary purposes, although alternating feet can be fitted when desired. Figs. 94, 95, and 96 show a pressure foot, collar, and spring. To fix this foot, remove the ordinary presser foot, turn the foot bar round by loosening the set screw, so that the groove made for the reception of the presser foot is directly behind the needle. Put on the collar (Fig. 95), then turn the foot (Fig. 94), and screw it in position. Next place the spring each side at the points D´ (Fig. 94), press down the collar (Fig. 95), and secure it by its set screw. The springs will act on each half of the foot, and keep them firm, though the material be uneven. The foot is particularly useful when overseaming a hem or the top band of a lady's boot, etc. To time the hook and needle, raise the connection rod so as to produce no throw, and tighten the screw as in Fig. 81. Then take off the needle plate and remove the slide E´ (Fig. 81) under which will be seen a crank and screws.

Now turn the machine back as at Fig. 88, lift up the bobbin case holder by pressing the catch T, and remove the bobbin case. Take off the hook guide cap by removing the two screws. Turn the hand wheel F (Fig. 81), toward you, until the needle bar has descended to its lowest point of travel, and loosen the crank screw farthest from you. Having done this, continue turning the hand wheel until the needle bar has risen. With the lowest mark level with the rocking frame casting, at this point, examine the hook, the point of which should be just up to the needle. If otherwise, loosen the other screw in the crank under the plate E´ (Fig. 81). Be sure the needle bar mark is level with the rocking frame, place the hook with its point just up to the needle, and tighten the crank set screw, being careful to have no end play to the short shaft. Again examine the needle bar and hook and if in proper time finally secure crank set screws and replace the fittings previously removed. Thread the machine as indicated (Fig. 81). Set the needle as high in the bar as it will go, with the long groove facing the operator, and thread the needle from the long groove side. The stitch regulator will be found at F´ (Fig. 81). The raising of it will shorten and the lowering of it will lengthen the stitch. The feed should be set about one thirty-second of an inch above the needle plate when at its highest point. To raise the feed, turn the machine back as in Fig. 88. Near to the part G (Fig. 88) will be found a large set screw. Loosen it and press the lever H (Fig. 88) upward raising the feed bar J as high as required, and tighten the set screw at G firmly. To remove the feed for cleaning and sharpening, take off the needle plate, under which will be seen two feed set screws. By unscrewing these, the feed can be lifted out.

One of the modern machines on the market is the Wheeler and Wilson, known as the Number 61, which is of rotary hook principle. The hook forms part of the under shaft, somewhat similar to that known as the D9 W and W. This hook and shaft revolves in two long bearings, and is held in position by a fluted wheel, which forms a collar at the right-hand end; thus when set properly no end play is permitted. This is an advantage over the boat-shaped shuttle machine. In the latter, the shuttle rocks about, becomes worn on the surface, often blunt pointed by striking the needle. As it wears, it becomes loose in the carrier, thus giving it freedom to roll away from or toward the needle, as well as making its action with relation to the needle very uncertain; and on account of the number of little loosenesses in fittings that this uncontrolled shuttle produces, missed stitches are frequent, and difficult to remedy, unless a number of new fittings are obtained or old ones repaired.

If there is any alteration required in the time of the rotary hook referred to, it can be made to the smallest fractional part of an inch very quickly and easily, and the movement can be relied on. The shaft to which it is secured is positive in its action (no variable motion), and at every stitch will meet the needle at exactly the same spot. This is an improvement over the boat-shaped shuttle, which has to have a certain amount of play or slackness to allow the loop to extricate itself; and this slackness increases as the machine is worked, so that the shuttle action often becomes very erratic.

Sometimes a carrier becomes sprained at one end, thus allowing the shuttle too much freedom. If at the heel end, the carrier should be removed and placed in a vise (heel uppermost). The heel should be given a light blow with a hammer, thus bending it into correct position, but it must never be allowed to incline toward the shuttle; it should stand perfectly square, and have the upper corners rounded off. If inclined toward the shuttle, the loop may occasionally hang on the heel, and cause an irregular tension.

In some machines the bobbin case holder (Fig. 97) rests on the casting seen in Fig. 81. It is secured by a large set screw, D (Fig. 97). For general use, this screw should be adjusted to allow number 40 cotton to pass freely over the bobbin case. The holder should not be removed, except when adjustment or repair is needed. The vertical portion is hinged to the base, and is kept upright by a lock spring and stud. If the spring is pressed from the stud, the vertical or ring part can be drawn back for placing in or taking out the bobbin case. The face of this portion must be perfectly square with the bottom of the base, otherwise it may cause considerable trouble. A slight adjustment can be made by loosening the two screws and moving the lock spring. A set square, E, should be used for testing the accuracy of this part as shown (Fig. 98), F representing the bobbin case holder.

The thread controller is similar in design to several others, but its movement is regulated by a small lever (Fig. 99) which receives its motion from a link attached to the foot bar bracket set screw, and this may be seen through a hole in the face plate. At G (Fig. 99), this lever engages with a stop washer located behind the thread controller plate. The washer is recessed to form a stop, at the same time to give sufficient clearance for the action of the spring; thus as the foot bar rises and falls, so does the thread controller spring. It is a common practice when cleaning a machine to remove the face plate, thus detaching the link referred to, and not connecting it again when replacing the face plate. From this, trouble arises. The tension pulley should be placed on its stud, the large boss being toward the face plate.

Thread a machine as follows: From the reel pin to nipper F (Fig. 81), round tension pulley G as the arrow indicates, down and into thread controller H up to take-up lever, threading over the roll and through the slot from the top of lever, then down the thread guide J, into guide K, and through the needle-eye from right to left.

In the ordinary boat-shaped shuttle, the looping up of the thread is not difficult. The needle, as it descends, enters an opening or cavity in the carrier, one side of which forms a support for the needle and guards it from contact with the shuttle point. Now, it is important that there be clearance for the needle. If the carrier stands so prominent as to spring the needle out of its true vertical line it will carry it away from the shuttle, and give the latter a chance to miss the loop.

Then there are carriers and drivers of varying heights. Those of the raised kind are preferable, if properly fitted. By "raised" is meant that they are higher, so as to form a better guard for the needle, as previously referred to (Fig. 100 A, in which E indicates the portion of raised carrier, F the shuttle point, and G the needle). But sometimes they are too high, and permit the needle-eye to be buried in the carrier, thus preventing the proper formation of the loop. This can be so bad as to cause very frequent missing; or it may be of such a slight character as to cause a miss-stitch only now and then. Occasionally, a needle bar has to be lowered, and that is sufficient to cause the same fault. The eye of the needle should always be about one thirty-second of an inch above the upper edge of the carrier, and the latter should be shaped so as to allow that amount of clearance the whole of the time the needle is rising to form the loop, until the shuttle point has well entered the same. Fig. 100 B shows how a carrier is hollowed to give the necessary clearance to the needle eye.

When a machine is reasonably tight in all parts, gauges and setting marks may be adhered to for the preliminary adjustments; and then if the machine works erratically, other adjustments must be made. Where no marks or gauges are furnished for the adjustment of the needle bar, it should be so set as to allow the shuttle or hook to enter the bold part of the loop formed from the needle. A good rule is to set the needle bar so that the needle-eye is about 1/32 inch below the point of the shuttle M (Fig. 100 C) when the latter is up to the centre of the needle groove. But this may have to be varied from 1/64-inch to 3/32-inch. In boat-shaped and similar shuttle machines, a good rule is to set the needle so that the eye N will pass just below the lower side of the shuttle O as the latter is passing through the loop as in Fig. 100 D, P, indicating the level of the bed plate.

II

MECHANICAL MOVEMENTS

What is meant by this term is that these devices are intended for the transmission of motion. Motion in mechanics may be simple or compound. Simple motions are those of straight translation, which if of indefinite duration must be reciprocating, or what is called oscillating or helical.

Compound motions consist of combinations of any of the simple motions. Perpetual motion is an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without, or which has within itself the means, when once set in motion, of continuing its motion perpetually, or until worn out, without any new application of external force. The machine by means of which it has been attempted, or supposed possible to produce such motion, is an invention much sought after, but physically impossible.

The illustrations herewith exhibit a number of devices of various kinds, well known to the practical mechanician and professional engineer, and usually called mechanical movements. It is estimated there are no less than 1,500 of these movements doing service at the present day; but many of them are, of course, quite complex, and difficult to master. In this book, I show about one hundred of the simplest sort, or those in common use. Their usefulness will at once be appreciated if we refer to Fig. 102, which shows a machine for grinding or breaking up substances within its capacity. It contains within itself the true principle of the little mill used to grind coffee. The word "grind" in this connection is scarcely the right one, as the mill rather "crushes" or breaks up, than grinds. You will notice coffee, ready for use, is coarse and unlike flour in texture, the latter being "ground" fine and smooth. In grinding, the abrading surfaces are brought very much closer together than in the breaking or crushing processes. In a coffee mill, the berries or grains drop into a vacancy, left between the revolving cone and the walls of the mill. The vacancy between the walls and the cone is a little less at the bottom where the crushed coffee is discharged, and this enables the small and large grounds to fall into the drawer. The detailed plan in illustration (Fig. 102) shows a mill complete, as well as the various parts. It will be noticed that the cone (Fig. 5), is corrugated or grooved as shown (Fig. 4). Figs. 6 and 7 show sections of lining at B and C (Fig. 3). A shows the hopper into which the coffee berries are placed before grinding. Figure 9 shows the crank detached, and Figs. 8 and 10 show the remaining parts of the machine, while Figs. 1 and 2 show the handle and drawer. The latter is to receive the ground or crushed coffee after it has gone through the mill. Further description is unnecessary if we take for example the movement represented at Fig. 150, which is a sort of ball-bearing motion, only instead of small balls wheels are used. Besides being made use of in bicycles in small balls, it is used as depicted for "hanging" grindstones, and for many other similar purposes.

The device also shown at Fig. 139, is one in common use. It is a modification of the sprocket wheel on the bicycle. Many of the devices shown herewith are rarely noticed because of our familiarity with them.

The action of pumps, the working of pistons, the changing of motion, and many other things are shown and explained in the little illustrations given in these descriptions, which do not pretend to be exhaustive, or even full.

Fig. 103. In this the lower pulley is movable. One end of the rope being fixed, the other has to move twice as fast as the weight, and a corresponding gain of power is consequently effected.

Fig. 104 is a simple pulley used for lifting weights. In this the power must be equal to the weight to obtain equilibrium.

Fig. 105. Blocks and tackle. The power obtained by this contrivance is calculated as follows: Divide the weight by double the number of pulleys in the lower block; the quotient is the power required to balance the weight.

Fig. 106 represents what are known as "White's pulleys", which can be made with separate loose pulley; or a series of grooves can be cut in a solid block, the diameters being made in proportion to the speed of the rope; that is, 1, 3, and 5 for one block, and 2, 4, and 6 for the other. Power as 1 to 7.

Figs. 107-108 are what are known as Spanish bartons.

Fig. 108 is a combination of two fixed and one movable pulley.

Figs. 111-113 are different arrangements of pulleys. The following rule applies to these: In a system of pulleys where each is embraced by a cord attached to one end of a fixed point, and at the other to the centre of the movable pulley, the effect of the whole will be the number 2 multiplied by itself as many times as there are movable pulleys in the system.

Fig. 114. Endless chain for maintaining power on going barrel, to keep a clock going while winding, as during that operation the action of the weight or mainspring is taken off the barrel. The wheel to the right is the going wheel, and that to the left the striking wheel. P is a pulley fixed to the great wheel of the going part, and roughened to prevent a rope or chain hung over it from slipping. A similar pulley rides on another arbour, _p_, which may be the arbour of the great wheel of the striking part, attached by a ratchet and click to that wheel, or to the clock frame if there is no striking part. The weights are hung as may be seen, the small one being only large enough to keep the rope or chain on the pulleys. If the part _b_ of the rope or chain is pulled down, the ratchet-pulley runs under the click, and the great weight is pulled up by _c_, without taking its pressure off the going wheel at all.

Fig. 115. Triangular eccentric, giving an intermittent reciprocating rectilinear motion, often used for the valve motion of steam-engines.

Fig. 116. Ordinary crank-motion.

Fig. 117. In this, rotary motion is imparted to the wheel by the rotation of the screw, or rectilinear motion of the slide by the rotation of the wheel. Used in screw cutting and slide lathes.

Fig. 118. Uniform circular into uniform rectilinear motion; used in spooling frames for leading or guiding the thread on to the spools. The roller is divided into two parts, each having a fine screw-thread cut upon it, one a right and the other a left-handed screw. The spindle, parallel with the roller, has arms which carry two half nuts, fitting to the screw, one over the other under the roller. When one half nut is in, the other is out of gear. By pressing the lever to the right or left the rod is made to traverse in either direction.

Fig. 119. A system of crossed levers, termed "lazy tongs." A short, alternating rectilinear motion of rod at the right will give a similar, but much greater motion to the rod at the left. It is frequently used in children's toys. It has been applied to machines for raising sunken vessels; also applied to ship pumps three quarters of a century ago.

Fig. 120. Centrifugal governor for steam engines. The central spindle and attached arms and balls are driven from the engine by the bevel gears at the top, and the balls fly out from the centre by centrifugal force. If the speed of the engine increases, the balls fly out from the centre, raise the slide at the bottom, and thereby reduce the opening of the regulating valve, which is connected with the slide. A diminution of speed produces an opposite effect.

Fig. 121. Water-wheel governor acting on the same principle as Fig. 120, but by different means. The governor is driven by the top horizontal shaft and bevel gears, and the lower gears control the rise and fall of the shuttle or gate over or through which the water flows to the wheel. The action is as follows: The two bevel gears on the lower part of the centre spindle, which are furnished with studs, are fitted loosely to the spindle, and remain at rest so long as the governor has a proper velocity; but immediately the velocity increases, the balls flying farther out, draw up the pin, which is attached to a loose sleeve which slides up and down the spindle, and this pin, coming in contact with the stud on the upper bevel gear, causes that gear to rotate with the spindle, and to give motion to the lower horizontal shaft in such a direction as to make it raise the shuttle or gate, and so reduce the quantity of water passing to the wheel. On the contrary, if the speed of the governor decreases below that required, the pin falls and gives motion to the lower bevel gear, which drives the horizontal shaft in the opposite direction, and produces a contrary effect.

Fig. 122. Another arrangement for a water-wheel governor. In this the governor controls the shuttle or gate by means of the cranked lever, which acts on the strap or belt in the following manner: The belt runs on one of three pulleys, the middle one of which is loose on the governor spindle, and the upper and lower ones fast. When the governor is running at the proper speed the belt is on the loose pulley, as shown; but when the speed increases, the belt is thrown on the lower pulley, and thereby caused to act upon suitable gearing for raising the gate or shuttle and decreasing the supply of water. A reduction of the speed of the governor brings the belt on the upper pulley, which acts upon the gearing for producing an opposite effect on the shuttle or gate.

Fig. 123. Another form of steam-engine governor. Instead of the arms being connected with a slide working on a spindle, they cross each other, are elongated upward beyond the top, and connected with the valve-rod by two short links.

Figs. 124, 125. Diagonal catch and hand-gear used in large blowing and pumping engines. In Fig. 124 the lower steam valve and upper eduction valves are open, while the upper steam valve and lower eduction valve are shut; consequently the piston is ascending. In the ascent of the piston rod the lower handle will be struck by the projecting tappet, and being raised will become engaged by the catch, so as to shut the upper eduction and lower steam valves; at the same time the upper handle will be disengaged from the catch, the back weight will pull the handle up and open the upper steam and lower eduction valves, when the piston will consequently descend. Fig. 125 represents the position of the catches and handles when the piston is at the top of the cylinder. In going down, the tappet of the piston rod strikes the upper handle, and throws the catches and handles to the position shown in Fig. 124.

Fig. 126. A mode of driving a pair of feed rolls, the opposite surface of which require to move in the same direction. The two wheels are precisely similar, and both gear into the endless screw, which is arranged between them. The teeth of one wheel only are visible, those of the other being on the back or side which is concealed from view.