Depth Of Teeth

Every gear cut with a different number of teeth to the inch, should be cut of a depth to the pitch line, to cor-ond with the number of teeth to the inch. This is called pro-portion. Therefore, if you cut a gear eight to the inch, the depth to the pitch line should be one-eighth of an inch, and the whole depth of the tooth would be two-eighths. Again, if you cut a gear twelve to the inch, the depth to pitch line should be one-twelfth of an inch, and the whole depth of tooth two-twelfths. And again, if you cut a gear twenty to the inch, the depth to pitch line should be one-twentieth of an inch, while the whole depth should be two-twentieths, and so on ad infinitum.

Measuring To Find The Number Of Teeth

To find the size a certain gear should be, for a certain number of teeth, is an easy matter if you study carefully these rules. If you want a gear with thirty-two teeth and eight to the inch, it should be four inches, measuring across the diameter to the pitch line, and the two-eighths outside of the pitch line would make it four inches and two-eighths. Again, if you want a gear with forty teeth, and ten to the inch, it should measure across the diameter to pitch line four inches, and the two-tenths outside the pitch line would make the whole diameter four inches and two-tenths. And again, if you want a gear with eighty teeth, and twenty to the inch, it should measure to the pitch line, across the diameter, four inches, and the two-twentieths outside the pitch line would make it four inches and two-twentieths, and these examples will form a rule for the measurement of all except bevel gears.

Bevel Gears

These are turned a certain bevel to correspond with each other, according to the angle upon which the shafts driven by them are set. For instance, if two shafts are set upon an angle of ninety degrees, the surfaces of the faces of these gears will stand at an angle of forty-five degrees. To get the surface of these gears in turning them, put a straight edge across the face, then set your level on an angle of forty-five degrees, and try the face of the teeth by placing the level on a straight edge. After turning the face of the teeth, square the outer diameter by the face Of the teeth: and to get the size to which you wish to cut, measure from the centre of the face of the teeth. Thus if a bevel gear is six inches in diameter, and the face of the teeth is one inch, you will measure from the centre of the face, and find it is five inches. On this line you calculate the number of teeth to the inch, and if you want a gear with twenty teeth, and ten to the inch, it should measure two inches across the face to the centre of the surface of the teeth; and if the face of the teeth were one inch in length, the diameter of the gear would be three inches, and the inside of the teeth would measure only one inch. Again if you want to cut a gear with forty teeth, and ten to the inch, it would measure four inches to the centre of the teeth on the suface. And if the surface of the teeth were one inch long, the diameter of the would be five inches, while it would only measure three inches inside the teeth. These examples will form a rule for all bevel gear.

Draw-Filing And Finishing

To draw-file a piece of work smoothly and quickly, it is ben to first draw-file it with a medium fine file, and finish with a superfine file. After doing this, polish the work with dry emery paper, and then with emery paper and oil.

Lining Boxes With Babbitt Metal

To line boxes properly, so as to insure their filling every time, it is necssary to heat the box nearly red hot, or at least not enough to melt toe metal. Then smoke the shaft where the metal is to he poured upon it. This insures its coming out of the box easily, after it is cold. After smoking the shaft, put it into the box or boxes, and draw some putty around the ends of them, for the purpose of stopping them, iking care not to press upon it, for if you do it will go into the box, and fill a place that ought to be filled with metal; and in the meantime your metal ought to be heated, and after you have poured it, let the box stand till it is nearly cold; drive out your shaft, and it is done.

Making Lining Metal

Melt in a crucible one and a half pounds of copper, and while the copper is netting, melt in a ladle twenty-five pounds of tin, and three of antimony, nearly red hot. pour the two together, and stir until nearly cool. This makes the finest kind of lining metal.

Putting Machines Together

In putting machines together no part should be finished except where it is necessary to make a fit, as it is sometimes the case that machinery is miscalculated, and by finishing it would be spoiled, while if it were not it might be saved by slight alterations in design. And again. in finishing certain parts before you get a machine together, you are unknowingly finishing parts not necessary to be finished, and making them of a shape anything but desirable. This rule, however, is not intended to apply to machinery being made to detail drawings.

How To Drill A Hole Where Yon Have No Reamer

It is sometimes necessary to drill a hole of an exact size to fit a certain shaft, and at the same time have it smooth without reaming it. This may be done, by first drilling a hole, a one-hundredth of an inch smaller than the size desired, and then making a drill the exact size and running it through to finish with. This last drill should have the corners of its Una rounded, like a reamer, and the hole should be finished without holding the drill with a rest.

Boring A Hole With A Boring Tool

In boring a hole with a boring tool, it is usually necessary to drill the hole first, and too much care cannot be taken in finishing. An iron gauge should be made first: is usually made of a piece of sheet iron or wire. The hole should then be drilled smaller than the size desired, and then bored to the required size, and it is impossible to bore a hole perfect without taking two or three light chips, mere scrapings with which to finish. Holes, in this way, may he bored as nicely as they can be reamed.

Squaring Or Facing Up Cast Iron Surfaces

A round end tool is best for this. A rough chip should first be taken off, over the entire surface to be faced. Then speed your lathe up and taking a light chip, merely enough to take out the first tool marks, run over the entire surface again. In turning up surfaces it is always best to begin at the centre and feed out, as the tool cuts freer and will wear twice as long.

Boring Holes With Boring Arbor

A boring arbor is a shaft with a steel set in it, for the purpose of boring holes of great length, and is designed to be used in a lathe. In doing this properly, you must first see if your lathe is set straight. If not, adjust it; having done this, put the piece of work to be bored in the carriage of your lathe, pass your arbor through the hole to be bored, and put it on the centres of your lathe. Having done this, adjust your work true to the position desired by measuring from the point of the tool, continually turning round the arbor from side to side of the piece to be bored, while you are bolting it to the carriage, and measure until it is perfectly true. Having done this, bore the hole, and take for the last chip only a hundredth of an inch. This makes a true and smooth hole. It is impossible to make a hole true with any kind of a tool when you are cutting a large chip, for the tool springs so that no dependence can be placed upon it.

How To Make A Boring Arbor And Tool That Will Not Chatter

Boring tools, when used in small arbors, are always liable to chatter and make a rough hole. To prevent this, the tool should be turned in a lathe, while in its position in the arbor, upon the circle of the size of the hole to be bored, and the bearing lengthwise of the arbor should be only as wide as the feed of the lathe; for if the bearing of the tool is on the face, the more it will chatter.