Modern Machine-Shop Practice Part 128

In Fig. 1862 is represented a nut threading or tapping machine. The vertical spindles have spring sockets in which the taps are held, so that they can be inserted or removed without stopping the machine. The nuts are fed down the slots of the inclined plates shown on the upper face of the circular base, and the spindles are raised and lowered by the pivoted levers shown. The nuts lie in a dish that contains water up to the level of the bottom of the nuts, the object being to prevent the taps from getting hot and therefore expanding in diameter. Upon the top of the water floats a body of oil about 1/2 inch deep, which lubricates the cutting edges of the tap. These machines are also made with six instead of four spindles, which in both machines run at different speeds to suit different sizes of nuts, and which are balanced by weights hanging inside the central hollow column or frame.

[Ill.u.s.tration: Fig. 1863.]

Fig. 1863 represents the socket for driving the tap, so devised that when the tap is strung for its intended length with nuts, the top nut releases the tap of itself, the construction being as follows: S is the socket that fits into the driving spindle of the machine; its bore, which fits the stem of the tap easily, receives two headless screws B, a pin P, which is a sliding fit, and the screw A. R is a ring or sleeve fitting easily to the socket, and is prevented from falling off by screw A. The tap is provided with an annular groove G. The flattened end of the tap pa.s.ses up between and is driven by the ends of screws B, the weight of the collar ring or sleeve R forcing pin P into the groove G, thus holding the tap up. When the tap is full of nuts the top nut meets face V of ring R, lifting this ring upon the socket and relieving pin P of the weight of R, the weight of the tap and the nuts then causes the tap to be released. By this construction the tap can be inserted or removed while the machine is in motion.

In Fig. 1864 is represented a rotary nut tapper, and in Fig. 1865, is also represented a sectional view of the same machine.

The tap driving spindles are driven from a central vertical shaft S, driven by bevel-gear B. The horizontal driving shaft operates a worm C, to drive a worm-wheel in a vertical shaft, which drives a pinion _a_, driving a spur wheel W in the base of the spindle head, by which means this head is revolved so as to bring the successive spindles in front of the operator. A trough is provided at T to cool the tap with oil and water after it has pa.s.sed through the nut.

Fig. 1866 represents a nut tapping machine designed for light work, the spindles are raised after each nut is tapped by the foot levers and rods shown, the latter connecting to a shoe fitting into a groove in a collar directly beneath the driving pulleys of the spindles.

Fig. 1867 represents a three-spindle nut tapping machine, in which the spindles are horizontal and the nuts are held in three separate heads or horizontal slideways and are traversed by the ball levers shown, and a self-acting pump supplies them with oil. The three spindles are driven by a cone pulley having four changes of speed to suit different diameters of taps.

PIPE THREADING MACHINERY.--In Fig. 1868 is represented a machine for threading and cutting off pipe of large diameter. This machine consists of a driving head corresponding to the headstock of a lathe, but having a hollow spindle through which the pipe may pa.s.s. The pipe is driven by a three-jawed chuck, and the threading and cutting off tools are carried on a carriage which has a threading head for ordinary lengths of pipe, and one for short pieces such as nipples, the latter swinging out of the way when not in use. Between these two is a pair of steadying jaws for the pipe. A side view of the front of the carriage is shown in Fig.

1869, H H, &c., representing the threading dies used for nipples. It is movable along a slideway E and pivoted upon its slider. The dies are carried in a chuck G, and are opened or closed by the lever N; at L is the handle for the screw that operates the guide jaws A A.

[Ill.u.s.tration: Fig. 1868.]

[Ill.u.s.tration: Fig. 1869.]

The threading head at H (right-hand end of Fig. 1868), is represented in Fig. 1870, being pivoted so that it also can be swung out of the way to permit of the removal of the pipe. The dies C are opened or closed by the hand wheel B, operating a worm mes.h.i.+ng into a segment of a worm-wheel upon the body of the head, the amount of motion being regulated by the stop screw at F, which therefore regulates the size to which the dies can be closed, and therefore the diameter of thread the dies will cut. The construction of the cutting-off head is shown in Fig.

1871, T representing the cutting tool which is operated by the hand wheel K. The carriage is fed or traversed by means of two pinions operated by the six-handled wheel shown at W, Fig. 1868; these two pinions engaging racks beneath the carriage, and near the inside edges of the bed, one of them being seen at the extreme right-hand end of Fig.

1868.

[Ill.u.s.tration: Fig. 1870.]

[Ill.u.s.tration: Fig. 1871.]

[Ill.u.s.tration: Fig. 1872.]

In Fig. 1872 is represented a machine for threading or tapping the fittings for steam and gas pipe. The tap is carried in the end of the vertical spindle, and the work may be held in the vice upon the work table, or if too large the table may be swung out of the way.

The general design of the machine corresponds somewhat to that of a drilling machine.

BROACHING PRESS.--Broaching consists in forcing cutters through keyways or apertures, to dress their sides to shape.

In Fig. 1873 is represented a broaching press. Its driving gear which is within the box frame is so constructed that it may be started and stopped instantly, notwithstanding its heavy fly wheel.

Figs. 1874 to 1877 represent the method of cutting out a keyway by broaching.

[Ill.u.s.tration: Fig. 1873.]

[Ill.u.s.tration: Fig. 1874.]

In Fig. 1874 A represents the end of a connecting rod having three holes, B, C, and D, pierced through it, their diameters nearly equalling the total finished width of keyway required. The punch D' is first forced through, thus making the three holes into one.

[Ill.u.s.tration: Fig. 1875.]

[Ill.u.s.tration: Fig. 1876.]

[Ill.u.s.tration: Fig. 1877.]

The [V]-shape of the end of the cutting punch D' tends to steady it while in operation, forces the cut outwards into the next hole, preventing them from jambing, and causes the strain upon the punch to begin and end gradually; thus it prevents violent action during the ingress and egress of the cutting punch. This roughing out process dispenses with the use of the hammer and chisel, and saves much time, since it is done at one stroke of the press. The next part of the process is the introduction of a series of broaches such as shown in Fig. 1875, the principles involved being as follow: It is obvious that from the large amount of cutting edge possessed by a single tooth extending all around such a broach, it would be impracticable to take much of a cut at once; hence a succession of broaches is used, some of them performing duty on the sides only, others at the ends only, but the last and final broach is usually made to take a very fine cut all over.

All these broaches are made slightly taper; that is to say, the breadth of the lower tooth at A in Fig. 1875 is made less than that at B, the amount allowed varying according to the dimensions and depth of the keyway.

The smallest of the set of broaches is entered first and forced through until its end stands level with the upper face of the work. Each broach is provided with a conical teat at one end and a corresponding conical recess at the other, so that when the second broach is placed on top of the first, the teat fitting into the recess below it, will hold the two broaches central one to the other.

The head of each broach is made somewhat conical or tapered, and sets in a corresponding recess in the driving head in the machine, which, therefore, holds the broaches parallel one to the other. A succession of these broaches is used, each requiring one stroke of the press to force it within the keyway, and another to force it out.

The following is an example of broaching, relating to which, the dotted lines shown on the broaches, Fig. 1876, indicate the depths and shapes of the teeth. The small end of each broach corresponds to the large end of the one that preceded it, which is necessary in order to permit it to enter easily. Of the ten broaches used the first two operate to straighten the side walls of the hole, No. 3 being the first to operate upon the circular corners, which are not cut to the rectangle until No.

8 has pa.s.sed through. But as the duty in cutting out the corners diminishes, the walls and ends of the hole are operated upon to finish them to size; thus broach No. 3 leaves the hole 1-1/8 or 1.125 inches wide, and 2.7501 inches long, which No. 4 increases to 1.1354 inches wide and 2.7605 inches long. This increase of width and depth, or breadth, as it may more properly be termed, continues up to the last or tenth cutter, which is parallel and of the same dimensions as the large end of cutter No. 9. Fig. 1877 gives two views of the No. 10 broach.

Broaches require a very free lubrication in order to prevent them from tearing the walls of the hole, and to enable them to cut easily and smoothly; hence it is found highly advantageous after the teeth are cut to cut out grooves or pa.s.sages lengthways of the broach, and extending nearly to the bottom of the teeth, which eases the cut as well as affords the required lubrication; but it is obvious that the finis.h.i.+ng cutter must not have such oil ways.

MODERN

MACHINE-SHOP

PRACTICE

[Ill.u.s.tration]

ILl.u.s.tRATED

MODERN

MACHINE-SHOP

PRACTICE

[Ill.u.s.tration: _Vol. II MODERN MACHINE-SHOP PRACTICE FRONTISPIECE_

COMPOUND MARINE ENGINE.]

MODERN

MACHINE-SHOP PRACTICE