MACHINES

The various machines used for manufacturing purposes are generally classified as follows:

Lathes; as, engine, turning, speed, grinding, cutting off, axle, wheel, screw machine, etc.

Planers; as, shapers, slotters, surface grinders, etc.

Milling machines; as, power, hand, duplex, universal, vertical, profiles, etc.

Drills; as, vertical or horizontal spindles, chucking and boring machines, etc..

Punches; as, presses, shears, etc.

Power hammers; as, steam, helve, trip, drop, etc.

There are numerous special machines which can be classed as modifications of some one of the above classes.

LATHE

By far the most important and the one which embodies the general principles of the other classes is the lathe. The figure on page 91 shows outline of a 12 inch by 5 foot engine lathe.

The size of a lathe is stated by the largest diameter it will swing on centers and the length of the bed. The carriage is moved along the length of the Vs of the lathe bed parallel to the axis of the driving spindle; the motion is imparted to carriage from the driving spindle either by the feed rod 11, through a belt transmission that is used when doing plain turning, or by the lead screw 10, and a system of change gears which is used when cutting screw threads.

The stepped cone pulley on driving spindle of lathe is belted to similar cone on countershaft except that the steps are in reverse order.

Example. When a countershaft makes 160 R. P. M., what is the R. P. M. of a lathe spindle, with pulley 7 in. dia. on counter, belted to a 4§ in. dia. on lathe spindle?

Solution. By formula for speeds of pulleys,

1. When the dia. of lathe pulley is 7§ in. and countershaft pulley is 4§, what is the R. P. M. of spindle if counter makes 160 R. P. M.?

2. Find R. P. M. of a lathe spindle when the pulley is 6 in. dia. and countershaft makes 155 R. P. M. with a pulley 6 in. diameter.

3. Find R. P. M. of a lathe cone pulley 8 in. dia. when the countershaft makes 170 R. P. M. and the pulley on countershaft is 5 in. diameter.

4. When a lathe cone pulley is 3 in. dia. and countershaft pulley is 11 in. dia., find R. P. M. of spindle when countershaft makes 165 R. P. M.

5. When a lathe spindle pulley is 8 in. dia. and countershaft runs 170 R. P. M. with a pulley 4 in. dia., what is the R. P. M. of the lathe spindle?

6. When a cone pulley is 3 in. dia. and countershaft runs 195 R. P. M. with pulley 91⁄2 in. dia. on countershaft, what is the R. P. M. of the lathe spindle?

7. The cone pulley of a certain lathe has steps 7 in., 6 in., 4 in., and 3 in. diameters respectively, belted to

the steps of a cone on countershaft, the diameters of which are as follows: 4 in., 63 in., 7§ in., and 9 in. When the countershaft runs 170 R. P. M. find the different speeds at which the work on the spindle may be driven.

8. A lathe has on its driving spindle a four step cone pulley with diameters as follows: 8 in., 63 in., 5 in., and 31 in. Belted to this cone is the cone on countershaft with steps 51 in., 63 in., 81⁄2 in., and 10 in. diameters respectively. Find the different R. P. M. at which work can be turned in the lathe, when the countershaft runs 180 R. P. M.

9. A lathe has a cone on the head spindle with steps 8 in., 6 in., 5 in., and 3 in. diameters respectively. If the countershaft runs 175 R. P. M. with a cone having steps 41⁄2 in., 64 in., 77 in., and 91⁄2 in. diameters respectively, what different R. P. M. may be given the work on the lathe centers?

BACK GEARS

The back gears are used to reduce the speed of lathe spindle, thus allowing a heavier cut to be taken at reduced speed.

On the back gear spindle are two gears fast to the same sleeve; on the lathe cone pulley is fastened a small gear which may be thrown into mesh with large gear on back gear sleeve; on the other end of the cone pulley fastened securely to lathe spindle is a large gear which is thrown into mesh with the smaller gear of back gears. When the back gears are not in mesh, a clamp nut fastens spindle gear securely to cone pulley.

Example. If a countershaft running 160 R. P. M. has a 5 in. dia. pulley belted to 8 in. pulley on lathe spindle, with gear fast to cone having 32 teeth and gear fast to spindle having 90 teeth, these being in mesh with back gears of 88 and 30 teeth respectively, what is the R. P. M. of lathe driving spindle?

1. When a countershaft runs 165 R. P. M. and pulley on countershaft is 4 in. dia. belted to a 7 in. dia. pulley on lathe spindle; and when the gears are the same as in above example, what is the R. P. M. of lathe spindle?

2. When the pulley on a countershaft is 7ğ in. dia. and the cone pulley is 4ğ in. dia. other sizes same as in problem 1 find R. P. M. of spindle.

3. When a countershaft makes 155 R. P. M. and the pulley is 8 in. dia. belted to lathe cone pulley 6 in. dia. with back gears 85 and 32 teeth, in mesh with 31 on cone and 84 on spindle, what is the number of R. P. M. of lathe spindle?

4. When a countershaft runs 185 R. P. M. and the pulley on countershaft is 5 in. dia. belted to an 8 in. dia. pulley on spindle with gears same as in problem 3, what is the number of R. P. M. of lathe spindle?

5. When a countershaft pulley 6 in. dia. running 160 R. P. M. is belted to a cone pulley 63 in. dia. and back gears with 75 and 20 teeth in mesh with 25 tooth gear on cone and 69 tooth gear on spindle, what is the number of R. P. M. of spindle?

6. When a countershaft pulley 5 in. dia. and running 225 R. P. M. is belted to a cone pulley on the lathe spindle 73 in. dia. with gears on back gear quill of 75 and 25 teeth in mesh with 25 teeth on cone pulley and 65 teeth on spindle, what is the R. P. M. that a piece will make on lathe centers?