Part 15 (1/2)

_Bending Pipes and Tubes_--It is difficult toa noticeable bulge at so er of this trouble if care is used, but iron pipe, having a seaiven special attention to avoid opening the sea if the tube or pipe is brought to a full red heat all the way around its circumference and at the place where the bend is desired Hold the cool portion solidly in a vise and, by taking hold of the free end, bend very slowly and with a steady pull The pipe must be kept at full red heat with the flames from one or more torches and must not be hammered to produce the bend If a sufficient purchase cannot be secured on the free end by the hand, insert a piece of rod or a s the bend, should ses appear, theywith the work

Tubing or pipesheld between two flat ht red heat The

Anotherco a solid cap or plug at each end

Thin brass tubing may be filled with melted resin and may be bent after the resin cools To re it to run out

Large jobs of bending should be handled in special pipe bending h for

WELDING

Welding with the heat of a blacksas fire, can only be performed with iron and steel because of the low heat which is not localized as with the oxy-acetylene and electric processes

Iron to be welded in this manner is heated until it reaches the tee color, not white, as is often stated, this orange color being slightly above 3600 degrees Fahrenheit Steel is usually welded at a bright red heat because of the danger of oxidizing or burning the metal if the temperature is carried above this point

_The Fire_--Ifcoal or, better still, from coke Gas fires are, of course, produced by suitable burners and require no special preparation except adjustree for the size and thickness of thewelded so that it will not be burned

A coal fire used for ordinary forging operations should not be used for welding because of the impurities it contains A fresh fire should be built with a rather deep bed of coal, four to eight inches being about right for work ordinarilyuntil the coal around the edges has been thoroughly coked and a sufficient quantity of fuel should be on and around the fire so that no fresh coal will have to be added while working

After the coking process has progressed sufficiently, the edges should be packed down and the firethe ends to be joined The fire should not be altered by poking it while theheated The best forh banks of coked coal on each side of theor channel froht down on top of the fire with a s to Weld_--If the operator is not familiar with the metal to be handled, it is best to secure a test piece if at all possible and try heating it and joining the ends Various grades of iron and steel call for different rees of heat, the properdetermined best by actual test under the hareat deal to do with their handling, especially in the case of a more or less inexperienced workular in shape, the h with before the metal is heated and the best positions on the anvil as well as in the fire deterard to the convenience of the workht to a welding temperature

Unnatural positions at the anvil should be avoided as good work is most difficult of perfor_--While there areon the relative shape of the pieces to be joined, the portions that are to eneral way, this shape being called a ”scarf” The end of a piece of work, when scarfed, is tapered off on one side so that the extree

The other side of the piece is left flat and a continuation in the saht plane with its side of the whole piece of work The end is then in the forure 50)

[Illustration: Figure 50--Scarfing Ends of Work Ready for Welding]

Scarfing may be produced in any one of several ways The usualheat, at which tier body of metal at the ends to be joined This body of th of the tapered portion being about one and a half ti handled Each piece should be given this shape before proceeding farther

The scarfthe ends, although this is not good practice because it is then iive the desired upset and additional metal for the weld This added thickness is called for by the fact that the metal burns away to a certain extent or turns to scale, which is reiven this shape they should not fit as closely together as ht be expected, but should touch only at the center of the area to be joined (Figure 51) That is to say, the surface of the beveled portion should bulge in the es are separated by a little distance when the pieces are laid together with the bevels toward each other This is done so that the scale which is formed on the metal by the heat of the fire can have a chance to escape froether

[Illustration: Figure 51--Proper Shape of Scarfed Ends]

If the scarf were to be for each other at the same time or before the centers did so, the scale would be imprisoned within the body of the weld and would cause the finished work to be weak, while possibly giving a satisfactory appearance from the outside

_Fluxes_--In order to assist in re surfaces as clean as possible while being joined, various fluxing

For welding iron, a flux of white sand is usually used, this ht to a red heat in the fire