of

If he would apply his knowledge

the laws of heat, expansion of metals, and friction, he would arrive at some such conclusion as this: The friction caused by the tool in removing material generated heat, and thereby heated the entire piece of stock. This caused the stock to expand. The expanThe expansion, which was mostly lengthwise, produced pressure against the centers. This extra pressure along with the heat, power, and lack of lubrication caused the steel to seize into the center and consequently it was twisted off.

Undue friction caused by lack of lubrication or overload has made it necessary to rebabbitt many a bearing in the machine shop. Friction generated heat, this heat accumulated caused still less lubrication and finally the metal in the bearing melted

out.

Every belt used in the shop transmits power by friction. The amount of power a belt is able to transmit depends upon four things, the width, thickness, speed, and pounds pull on it.

There are many machines driven by friction wheels and discs where the load is not heavy. They are very satisfactory.

Bear in mind that every time you throw in the clutch on your lathe you are applying friction to some surface.

Heat and Expansion of Metals.

Often times it is necessary to shrink rings, collars, and wheels on shafts. Then the expansion coefficient of the various metals has to be taken into account, and

with a complete knowledge of how much these metals expand when heated a certain amount, a machinist is able to make a satisfactory fit.

Mixing certain unlike metals together produces an alloy that neither shrinks nor expands when heated and allowed to cool. This fact is taken advantage of in the manufacture of babbitt metals. Good babbitt metal does not shrink upon cooling from the melted state after it is poured. This makes it tight and firm in the bearing.

In doing accurate measuring the machinist must exercise care to see that both his measuring tool and the work being gauged are at exactly the same temperature. A difference in their temperatures will give an untrue reading on the gauge.

Many solid brass journals in which high speed shafts run are made a tight fit when they are cool so that when they are warmed up to the proper running temperature they will be just a good running fit. In such a case the difference in expansion rates of the metals must be taken into account.

The patternmaker has to take into account also the fact that when molten metal cools it shrinks an appreciable amount. In order that the cooled casting shall be of the proper size, he has to allow a certain amount oversize on all patterns according to the metal from which the castings are to be made.

Bringing the subject closer to home; even in the making and fitting of pistons in a gas engine the expansion of the iron due to the heat of the explosions, has to be allowed for.

Gravitation.

When lining up machines with their countershafts and leveling them, gravity has to be reckoned with if the best results are to be obtained. It is gravity that causes the plumb bob to do its work in this case. Belts do not run well on shafts that are not level, nor are machines always as accurate when not leveled. A lathe with a twisted bed can not be expected to do as

Centrifugal Force.

Whenever we see sparks leaving an emery wheel we see the result of centrifugal force in action. It is also this same force acting that causes emery wheels to explode and fly in all directions.

Centrifugal force also causes wheels that are not balanced to vibrate and jump while in motion.

When we enter the engine room and see how smoothly and steadily the large engine running a whole factory operates, we will also see another application of centrifugal force. The weights of the governor that controls the engine's speed are thrown out by this force.

By utilizing the laws and facts concerning centrifugal force and gravitation we are enabled to balance large pulleys and fly wheels so perfectly that they will run for hours when once set in motion on true bearings.

Noncompressibility of Liquids.

In the large hydraulic presses used for pressing wheels on to their shafts, forming boiler and tank heads, riveting, punching and bending, advantage is taken of the fact that liquids are practically noncompressible.

The small hydraulic jack used about machines is another instance of the application of hydraulics in a practical way. There are many more applications in modern shops.

Compressibility of Gases.

Were it not for the fact that gases are compressible, and especially air, there would be no rapid fire riveting hammer in use in the shops. There seems to be

a

medium for operating riveting and chipping hammers, riddlers, moulding machines, breast drills, air chucks and small hoists.

A study of pneumatics will reveal much to the student, and there are still more ways to take advantage of the fact that gases are compressible. What happens when a gas is compressed, what happens when it expands, how far it can be compressed, and what will happen when the limit is reached? All are questions for

even a machinist to think about. Machines and Mechanical Motions.

Machines are all a combination of levers, beams, incline planes, and cylinders rotating on shafts. Every piece of machinery in the shop is a unit embodying nearly everyone of the above elements and perhaps more.

Every inventor develops his ideas in accordance with his knowledge and understanding of the fundamentals of machines and their design. The machine designer, because he has command of higher mathematics and science, is able to bring out and develop new and wonderful applications of the fundamentals of machines. Electricity and Magnetism.

Electricity has become so commonplace in our everyday life that we pay little attention to it and its application even to our work. To understand some of the fundamentals of this strange force that travels in or about a metallic conductor may at some time aid us in avoiding accidents as well as help us in the execution of our daily tasks in the machine shop.

The fact that heat is developed when an excess of current is allowed to pass through certain kinds of metallic conductors is taken advantage of in the electric furnaces now used in producing steels. The later types of small furnaces used for heat treating of tool steels are also heated by the electric method.

The sensitive pyrometer used to gauge

the exact degree of temperature in one of these heat treating furnaces is an electrically operated instrument. The rod or coil that is placed in the furnace is a small thermo couple that produces an electric current. Connected with this coil is an exceedingly sensitive voltmeter. The hotter the furnace becomes, the greater the amount of current, consequently the voltmeter which is not graduated into volts but degrees of temperature tells the degree of heat that exists within the furnace. In the construction of the pyrometer advantage is taken of the fact that when two metals with dissimilar electrical resistances are connected together and heated, a current of electricity is produced.

Electricity is also used in two different ways in shops to do spot and arc welding. Spot welding is used where two rods, wires, loops or sheets are to be united. Arc welding is used for much the same work as acetylene.

Magnetism, a state within a piece of iron or steel that causes it to draw other pieces of the same metal towards it or repel them is produced by electricity. In the shop it is used to separate the iron scrap from the brass and aluminum, to charge large lifting magnets and magnetic chucks. Light.

Were a machinist to possess a thorough knowledge of light and laws pretaining to it he could solve many of his problems. strange as it may seem. The laws controlling the refraction and reflection of light waves have been applied in the manufac ture of gauges. Just recently a large tool manufacturing concern in the U. S. brought guaranteed accuracy within a millionth part of an inch. This accuracy was made possible by using light waves to test. Many expert tool and die makers now have studied the process and are able to get more accurate work than before. Light can be seen thru a space much less than one thousandth part of an inch in width. This fact alone is valuable to know.

There are hundreds of other applications

of physics to practical shop problems that exist today. The job that seemed beyond us when we did not understand the physics connected with it becomes easy and interesting when we have studied that subject.

WHERE CHEMISTRY APPLIES IN THE EVERY DAY SHOP JOB.

Perhaps there is no branch of science that has helped to bring the machine trade ahead as has chemistry. Thru chemical research and experimentation the best and strongest kinds of alloy steels and metals used by the machinst have been developed. The foundryman has to seek the advice of the chemist to solve his casting problems, the die caster has to do the same in order to get a strong alloy to use in his casting machine. High speed and alloy cutting steels have been originated by the chemist. The proper heat treatment of irons and steels is first determnied by one versed in metalurgical chemistry. Oxygen.

Oxygen has a great appetite for iron and steel when they are heated. Certain amounts of burned iron or iron oxide, when present on the surface of the steel, tell us that the steel has been heated to a certain temperature. This fact has been made use of for years in determining the degree of hardness within a hardened and tempered piece of steel or tool.

Malleable castings are made by packing the common casting in boxes filled with pure iron oxide or scale, closing them securely, and heating them to a red heat for several days. This treatment allows the oxygen combined with the iron in the scale to unite with the carbon mixed with the iron in the castings and thus frees the castings of the carbon and renders them bendable and less breakable.

Every heat treater of steels understands what will happen to his tool steels if he does not have the mixture of air and gas or air and oil mixed in the right proportions. Generally too much free oxygen the furnace flame will scale his work, and sometimes burn out the carbon, thus rend

in

ering his tool or steel useless. Even in the forge too much oxygen will produce bad results. Carbon.

Every expert tool and diemaker uses his knowledge of the effects that carbon has when present in tool steels. Whether or not he knows it he is acting in accordance with the chemical changes in the steel when he hardens and tempers it.

It is also a well known fact that when sand and carbon are placed in an electric furnace and fused together a very hard substance called Carborundum or Crystalon is produced. This substance and others produced in a similar manner are used to make abrasive wheels of all descriptions. Modern machine practice uses millions of wheels of this kind now to do work formerly done on lathes, and other jobs that were not thought possible before abrasives were developed.

Acids and Salts.

Various acids and salts are used daily in connection with the machine trades. Soldering fluxes, welding compounds, and etching fluids belong to one or more of the above classes.

Acid solutions are used to remove the heavy scale formed on drop forgings. Salt solutions are used to produce sudden cooling, color effects and for electro-plating. Acid solutions are used to treat sheet iron before it is tinned or galvanized. Parts of cam shafts used in auto motors are now copper plated in a copper cyanide solution to prevent carbonizing except where desired. The steel rule the machinist uses in his daily work is an acid etching. Micrometer dials on machines are made in the same manner as scales. Even master plates from which all disc phonograph records are made is produced by acid etching.

In Conclusion.

These few simple instances of where science enters into the solution of shop problems may show to a certain degree the value of knowing something about the

subject. It should not be forgotten that the mere knowing of these things ought to be incentive enough to induce every machine shop student to study his science. lessons. It is much easier to learn this related subject matter now while one is at school than it will be later when every day is a work day and every evening and night one for rest.

It has taken centuries to bring science to the place where it now is. The laws and facts that have been discovered are recorded in understandable form for our benefit. Why throw away the opportunity to profit by the experiences of many learned scientists and mathematicians. Rather let us see where we can reap benefit from some of their labors by making use of some science in our daily shop life.

A FIGURE PUZZLE.

Open a book at random, and select a word within the first ten lines, and within the tenth word from the end of the line. Mark the word. Now double the number of the pages, and multiply the sum by 5. Then add 20.

Then add the number of the line you have selected.

Then add 5.

Multiply the sum by 10.

Add the number of the word in the line. From this sum subtract 250, and the remainder will indicate in the unit column the number of the word; in the tens column the number of the line, and the remaining figures the number of the page.-Progress.

Murphy had lost his eye and had with pride secured a glass one to replace it. One day he was on guard duty without his false eye.

"You, Murphy, you're not dressed properly. Where's your eye?" asked the O. D.

"Sure, sorr, Oi left it in me tent to keep an eye on me barrack bag while Oi am on guard."

Next to marriage, the choosing of a life work is probably the most important step taken by a young man. There are a good many things about the two steps we can compare and contrast.

In this world there are so many fine girls that a fellow ought to find no difficulty in choosing a good one. There are so many fine chances in positions that a fellow should find little trouble in picking out a good one. The difficulty is to find. just the right girl and just the right job.

If you lose your job, you must start

over again at a new one. If you choose the wrong wife you are in trouble. Both are perilous and critical enterprises.

If you get a position in which you fail or which you don't like, you may get another. In fact, you may get many others, if you are not careful, until you become a drifter. If you make a mistake in choosing the right girl for better or worse, you find it much more difficult to correct the mistake. So does she.

If you lose wife or position, in either case you are out of luck. A change cannot be made without loss to you and the business or to you and the girl.

All these things make the choice of a life work almost as important as choosing a life partner. Out of the experience that many men have gained in life, some very

only rules of common sense, have been formed.

If you

came back from the war,

it would be wise to go back to the old work and to the old employer to get your feet on the ground again.

If you are picking your first job after leaving school, look into it pretty carefully before you decide. Stick to your old occupation until you find a better one. Don't jump to another line of work until you are sure it offers better opportunities than the old one. Look before you leap. Consider that when you change to another line of work you may be scrapping the one great wage earning asset you have, that is, the skill and experience you have built up in the old work.

It may take you a long time to gain it in a new line. The place in which your previous knowledge and skill should command the best return is the industry or business you have been following. Why not fix your attention on the work ahead of you and aim for that?

The best way to make your previous skill and knowledge worth most is to train yourself for promotion. If you determine to shift to a new business, get all the facts about it before you make the change. Find out what your chances will be of holding a good job twenty years from now. Do not be led astray by the alluring offer of large wages at the present time in a temporary line of work.

Choose an employer in a business in which the positions have been so carefully analyzed that the line of promotion is definite and sure for the willing and competent man. Learn what this line is and get yourself ready to move up when vacancies occur and the business grows.

Above all be sure the work is something you would like to do and for which you are fitted both from the standpoint of your interest and your kind of ability.

Minneapolis young men are fortunate to be located in a city where the opportunities