1032 



TUBES 



converting the ribbon of brass into a tubular form, the edges of the ribbon forming a 

 longitudinal opening down the entire length of the partially-formed tube : this longi- 

 tudinal opening or slit and the edges of the metal are brought closer together by re- 

 moving the wedge D. and checking the passage of the ribbon, when the pull of the 

 drawbench brings the two edges of the partially-formed tube closer together. Tubes 

 of larger diameter and of thicker metal, however, require the breadth of metal neces- 

 sary for their construction to be rendered concave in their entire length, to facilitate 

 the operation of turning the metal up ; and this is done by means of a pair of rolls, 

 one of which has on it a series of projecting beads of varying diameters in convexity ; 

 the corresponding roll has corresponding concave grooves, as shown in fig. 2045. The 



2044 2045 



2046 



B c 



width of metal is presented to that portion of the roll which will impart the necessary 

 degree of concavity to the strip in its entire length. It is then passed through the 

 rolls, and in passing through is converted into a concave trough-like piece of sheet 

 metal. As in former descriptions in reference to thin metal, the end of the metal is 

 beaten into a tange to be caught by the plyers of the drawbench. This tange is passed 

 through the drawing tool, laid hold of by the plyers, and drawn through the tool ; its 

 edges are drawn together by a final pinch or pull of the drawbench. The next opera- 

 tion is that of soldering or uniting the two edges of the metal together : previous to 

 this the partially-formed tube is annealed, and immersed in a solution of weak acid, 

 which removes the scale and grease used in lubricating the metal to facilitate its pas- 

 sage through the tool in turning up from a ribbon to its tube-like form. After the 

 acid is removed by immersion in pure water, the open-jointed tube is in a condition to 

 be soldered at the joint ; previous, however, to this it is necessary to bind the tube 

 round with wire at greater or less distances, in order to prevent the seam from opening 

 in the fire when the metal becomes relaxed with the heat of the soldering stove. The 

 wire used is annealed or soft-iron wire ; it is passed round the tube, and its ends 

 twisted together ; see fig. 2046. Along the open joint is laid granulated brass solder, 

 mixed with borax, the latter acting as a flux, at the same time keeping the edges of 

 the joint clean. The solder fuses at a lower temperature than the tube to be soldered. 

 When the solder has been distributed along the seam of the tube (this and the pre- 

 ceding operation usually being performed by women and girls), the tube is in a con- 

 dition to be passed into the hands of the solderer. The soldering furnace or stove 

 has a provision for a fire 6 or 7 feet long, which burns in a firebrick square tunnel, 

 open at both ends for the introduction of the unsoldered tube at one end, and when 

 soldered to remove it at the opposite end. The fuel used is small coke or ' breezes ; ' 

 coal until reduced to coke would prevent by its smoke and consequent low heat the 

 fusion of the solder. Fig. 2047 shows a section through length of a soldering stove, 

 and fig. 2048 a perpendicular section of the same. A A A A A, fig. 2047, is brickwork ; 

 D D, dampers, to regulate the draught of fire and increase or diminish its intensity ; 



2047 



2048 



c c are iron bars, on which those rest 

 on which the fire is placed ; and u B, 

 the tube which is to undergo the 

 soldering process. The pipe is in- 

 serted at one end ; the fire playing 

 under and over it, speedily heats the 

 tube ; the necessary heat to fuse the 

 solder arrived at, it fuses and unites 

 the two edges of the metal, and the 

 operation of soldering is completed. 

 If the tube has been bound round 

 with wires, these are untwisted and taken off, and in order to got rid of the borax, the 

 tubes are immersed in long troughs of wood, lined with lead and filled with a ' pickle,' 

 composed of a solution of oil of vitriol and water. After remaining in this bath for a 

 limited period, and being rinsed out in water, the superfluous solder is filed off, and 

 tho tube is in a condition to receive its final finish in the drawbench, which is effected 

 by placing a drawing-tool so formed that its internal diameter has more friction on the 

 tube than the one used for ' turning up ' the tube from the ribbon, the tange of the tuba 



