it will pass through the die and can be grasped by the pulling drawhead as shown at A, Fig. 180. The drawhead is made to engage with a travelling chain B, and thus pulls the tube through the die and over the conical mandrel shown at M, Fig. 180. The principal novelty of the machine employed by the

Tube Company in the improved drawing process consists in the use of a pushing as well as pulling drawhead, of a peculiarly shaped die, and of the method of applying power to move the drawheads. A complete drawing of the machine is shown in side elevation in Fig. 181 and in end elevation in Fig. 182. The drawheads are shown in plan and elevation in Fig. 183, and

Carpenter

FIG. 183.

consist of both a push and a pull head, one of which is located on either side of the die, and each of which carries a chuck for clasping the pipe and a grip by means of which it can be attached to or detached from the rope used for moving the drawheads. The pushing drawhead is used only to crowd

the tube through the die. It is attached to the tube about one foot from the free end of the tube and in such a manner as not to interfere in any way with the free motion of the particles of the pipe due to the increase in length in the drawing process. After the tube is passed through the die it is caught by the pulling draw head which is located on the other side of the die, and is then drawn in the usual manner through the die; simultaneously with the attachment of the pulling drawhead the pushing drawhead is released. The construction of the pushing drawhead was only accomplished as a result of numerous experiments, and it was believed generally by those familiar with the process of drawing that the operation of pushing the tube into the die was impossible. The use of the pushing die saves all work of preparation of the ends of the pipe to make them enter the die and all waste due to the production of bad and ragged ends on the drawn tube. In the drawing machine the drawheads are moved by being attached to a rope by means of a grip instead of being pulled, as in the ordinary process, by a chain. Considerable experimenting was required in order to produce a satisfactory drawing machine. The form of the machine which is in use is shown in drawing Fig. 178, from which it will be noted that the rope R for the draw passes beneath the draw frame AB and is made to take three wraps around two grooved pulleys C and D, thence over an inclined idler E, which returns the rope to the central position of the frame; the slack of the rope is taken up by a tightner pulley T, of the usual construction. The machinery of each drawing frame is operated by a 15 horse-power induction motor K, which is connected by spur and screw gearing to the driving pulley of the rope drive. The starting bar for the motor is in convenient reach of the operator, and is connected so that the motor can be run in either direction as required. Ropes 1 inches in diameter are employed, and have been found to have a reasonable life, the cost of repairs being less than when chains are used for a similar purpose. The practical advantage which the rope has been found to possess over the chain for drawing purposes is due to its elasticity and stretch, by means of which the tube is drawn gradually through the die, and there is an entire absence of jerky motion, which is so destructive to tubes when the drawing is performed by chains or other rigid material. The improvement on the character of the stock due to the yielding nature

of the pulling mechanism is decidedly marked. The drawhead clutch is arranged with a safety opening device, so that the clutch would be released if by any means the drawheads were carried beyond the limit of safe travel.

The method of cleaning the scale from the tube is found to have an important influence on the quality of the tubing, and has been one of the most difficult problems to solve successfully. The use of the ordinary open bath with 8 to 10 per cent. acid was found to injure the tubing materially, and after extensive experiments a more satisfactory process of cleaning was discovered, in which the use of less than 2 per cent. acid is found to clean successfully a rack of tubes in a length of time not exceeding 15 minutes. These good results are due to the fact that the tubes are immersed in a vertical position with both ends open and in such a manner as to allow a free and uninterrupted circulation of the liquid of the bath.

In the practical operation of the plant the tubes to be drawn are passed in succession and at a rate of 24 feet per minute through the different dies until they have reached the required diameter and gauge, being annealed and cleaned after making each pass. During the operation of drawing, whenever the length of the drawn tube exceeds from 18 to 20 feet, it is immediately cut into lengths of 9 to 10 feet, and the process of drawing continued. At present the original tube before the drawing begins, which is employed for bicycle tubing, is 13 inches external diameter.

A general view of the drawing-room is shown in Fig. 184, from which it will be noticed that there is an entire absence of overhead shafting or of moving machinery of any kind, except that connected to the draw benches. An observer would also be struck with the cleanliness of the room and of the dress of the workmen and of the entire absence of grease or oil on the floor. This latter result is obtained by immersing the tubes, before each process of drawing, in a hot bath of greasy material, which, when cooled to the ordinary working temperature, has the consistency of wax or varnish, which adheres to the tubing in a very thin coat, and, although sufficient to lubricate the dies, is insufficient to fly off and cover the floor and working machinery with layers of grease.

The annealing is done in a natural gas furnace, the tubes being moved by automatic machinery at a rate just sufficient to

anneal the tubes with one passage through the furnace. The unannealed tubes, while harder then the annealed, were found, as will be shown by the tests later, to have considerable elasticity and to be of quite uniform quality.

The building is a model workshop of its kind, and was designed by P. J. Fickinger.

It is provided with both side and roof lights, the roof windows being arranged in such a manner that the sashes are vertical and the light enters from the north, thus giving the shop light without any of the glare of direct sunlight, and rendering the use of shades unnecessary.

Tests of a number of samples of the McCool tubes were made in the laboratory of Sibley College, Cornell University. The

FIG. 185.

tests undertaken were such as would bring out the weakness, if any existed, due to the use of the welded joint in the original stock.

Transverse Tests.-Test No. 2, gauge 18, annealed, external diameter 0875 inch, internal diameter 0.785, was carried on supports 18 inches apart; it supported a centre load at elastic limit 340 pounds, at yield point of 370 pounds, and at maximum