of a lathe is determined by the length of a piece of work that can be turned. This measurement is taken from the points of the live and dead centers when the tail stock is drawn back the full extent of the lathe bed. Fig. 1 shows a turning lathe with sixteen principal parts named. The student should learn the names of these parts and familiarize himself with the particular function of each.

CARE OF THE LATHE

The lathe should be oiled every day before starting. At the end of the period the lathe should be brushed clean of all chips and shavings, after which it should be rubbed off with a piece of waste or cloth to remove all surplus oil. All tools should be wiped clean and put in their proper places. If a student finds that his lathe is not running as it should, he should first call the attention of the instructor to that fact before attempting to adjust it; and then only such adjustments should be made as the instructor directs.

SPEED OF THE LATHE

The speed of the lathe should range from 2400 to 3000 revolutions per minute when the belt is on the smallest step of the cone pulley. At this speed stock up to 3" in diameter can be turned with safety. Stock from 3" to 6" in diameter should be turned on the second or third step, and all stock over 6" on the last step. The speed at which a lathe should run depends entirely upon the nature of the work to be done and the kind of material used. Pieces that cannot be centered accurately and all glued-up work with rough corners should be run slowly until all corners are taken off and the stock runs true. At high speed the centrificial force on such pieces is very great, causing the lathe to vibrate, and there is a possibility of the piece being thrown from the lathe thus endangering the worker as well as those around him. After the stock is running true the speed may be increased.

Fig. 1. - Wood Turning Lathe

TO FIGURE THE DIAMETER OF PULLEYS

Suppose a motor runs 1500 R.P.M. and is fitted with a 4" pulley. Suppose also, a main shaft should run 300 R.P.M.

Then, 1500 : 300 :: x : 4;
Or, 300x = 6000,
x = 20, or the diameter of the large pulley on the main shaft.

Suppose again that a line shaft runs 300 R.P.M., and a counter shaft 600 R.P.M. The counter shaft has a pulley 4" in diameter. The pulley on the line shaft must then have a diameter of 8".

300 : 600 :: 4 : x;
Or, 300x = 2400,
x = 8"

Suppose the cone pulley on the counter shaft runs 600 R.P.M.; a lathe spindle runs 2200 R.P.M., when connected with the small cone pulley which has a diameter of 3". The large cone pulley has then a diameter of 11".

600 : 2200 :: 3 : x
Or, 600x = 6600;
x = 11"

RULES FOR FINDING THE SPEEDS AND SIZES OF PULLEYS

1. To find the diameter of the driving pulley:

Multiply the diameter of the driven by the number of revolutions it should make and divide the product by the number of revolutions of the driver. (20 x 300 = 6000; 6000 ÷ 1500 = 4"--diameter of motor pulley.)

2. To find the diameter of the driven pulley:

Multiply the diameter of the driver by its number of revolutions and divide the product by the number of revolutions of the driven. (4 x 1500 = 6000; 6000 ÷ 300 = 20"--diameter of the driven pulley.)

3. To find the number of revolutions of the driven pulley:

Multiply the diameter of the driver by its number of revolutions and divide by the diameter of the driven. (4 x 1500 = 6000; 6000 ÷ 20 = 300--revolutions of driven pulley.)

POINTS ON SETTING UP LATHE AND SHAFTING

The counter shaft should be about 7' above the lathe. A distance of 6' from the center of the shaft to the center of the spindle is sufficient. In setting a lathe or hanging a counter shaft it is necessary that both be level. The counter shaft must be parallel to the line shaft. When the counter shaft is in position a plumb bob should be hung from the counter shaft cone to the spindle cone; the lathe should be adjusted so that the belt will track between the two cone pulleys. The axis of the lathe must be parallel to that of the counter shaft. The lathe, however, need not be directly beneath the counter shaft as the belt will run on an angle as well as perpendicular.

CHAPTER III

WOOD TURNING TOOLS

A wood turning kit should consist of one each of the following tools. Fig. 2 shows the general shape of these tools.

1¼" Gouge
¾" Gouge
½" Gouge
¼" Gouge
1¼" Skew
¾" Skew
½" Skew
¼" Skew
⅛" Parting Tool
½" Round Nose
¼" Round Nose
½" Square Nose
¼" Square Nose
½" Spear Point
½" Right Skew
½" Left Skew
Slip Stone with round edges
6" Outside Calipers
6" Inside Calipers
8" Dividers
12" Rule
½ pt. Oil Can
Bench Brush

GRINDING AND WHETTING TURNING TOOLS

Skew Chisel

The skew chisel is sharpened equally on both sides On this tool the cutting edge should form an angle of about 20° with one of the edges. The skew is used in cutting both to the right and to the left, and therefore, must be beveled on both sides. The length of the bevel should equal about twice the thickness of the chisel at the point where it is sharpened. In grinding the bevel, the chisel must be held so that the cutting edge will be parallel to the axis of the emery wheel. The wheel should be about 6" in diameter as this will leave the bevel slightly hollow ground. Cool the chisel in water occasionally when using a dry emery. Otherwise the wheel will burn the chisel, taking out the temper; the metal will be soft and the edge will not stand up. Care should be exercised that the same bevel is kept so that it will be uniformly hollow ground. The rough edge left by the emery wheel should be whetted off with a slip stone by holding the chisel on the flat side of the stone so that the toe and heel of the bevel are equally in contact with it. Rub first on one side and then on the other. The wire edge is thus worn off quickly as there is no metal to be worn away in the middle of the bevels. The chisel is sharp when the edge, which may be tested by drawing it over the thumb nail, is smooth and will take hold evenly along its entire length. If any wire edge remains it should be whetted again.

Fig. 2. - Lathe Tools

Gouge

The gouge used in wood turning is beveled on the outside and is ground so that the nose is approximately semi-circular in shape. The tool is a combination of the round nose chisel and the ordinary gouge. The bevel should extend well around to the ends so that the cutting