TUBES 



1033 



2049 



is passed through the tool, find laid hold of by the plyers attached to the chain of tho 

 bench, the wheels are thrown into gear, and the tube is drawn through and receives in 

 the operation the fine smooth surface apparent on well and carefully drawn brass tubes. 



The Ornamentation of Tubes in Brass, $c. The action of the drawbench being, as 

 its name indicates, to draw or pull a partially-formed cylinder through a steel tool or 

 die, the tool or die being placed at right angles, the aperture in the centre of the tool 

 being placed parallel to the surface of the top of the drawbench, suggests that if the 

 tube is cylindrical, reeded, fluted, square, oval, hexagonal, polygonal, or angular in 

 its entire length, any of these forms may readily be produced, by simply substituting 

 a draw-plate, the aperture of which corresponds to the external configuration of the 

 desired form of the tube. Tubes which have spiral, concave, or convex twists or 

 threads, traversing their entire length, however, require pecu- 

 liarly formed tools or dies, and an arrangement in their use to 

 meet the requirements of the desired style of ornamentation. 



Tubes shown in fig. 2049, ABC, are produced from metal, 

 first ornamented by the introduction of perforated sheet zinc 

 between two sheets of metal, and in that position the three 

 sheets are passed through a pair of rolls, the perforated zinc, 

 by the pressure in rolling, being forced into the surface of 

 the brass to be ornamented ; the raised portions of ornament 

 in relief; as the quatrefoils, disks, and diamonds, correspond- 

 ing to the perforations in the zinc introduced between the 

 two sheets of brass to be ornamented. This style of orna- 

 mentation of flat metal was introduced by K. F. Sturges, of 

 Birmingharii, in the year 1852, and is identical with the pro- 

 cess employed in the production of the plates used to produce 

 impressions from natural objects, and known as Nature- 

 Printing. The same effect would be produced by steel rolls cut with ornamental 

 devices on their outer circumference, but the expense of such rolls being very great, the 

 perforated zinc, considering the limited character of the demand for such tube?, is more 

 economical. The ornamental metal being cut up into the breadth required, is made 

 into tube by the process already described as that by which ordinary soldered cylindrical 

 brass tube is made. 



Another variety of ornamental tube is produced by a very ingenious process intro- 

 duced also in the year 1852, by Mr. Fearn. In this process the ornament is impressed 

 on the surface of the tube after it is made : the tool used is formed by a construction 

 of rolls as shown at.%. 2050, the internal or hollow surface of the rollers which press 



2051 2052 



upon the tube being cut with the necessary design, the cylindrical or other tube to be 

 ornamented is supported internally by a mandril, and in passing it through the com- 

 bined tool or die, tho rollers, A A A A, revolve and indent the design cut on their cir- 

 cumference into the surface of the plain tube to be ornamented. Fig. 2051 shows the 

 style of ornament produced by this process : A being produced on a steel mandril as an 

 internal support ; in B and c the convexity or relief of the ornamental beads being 

 greater, it is produced by substituting for the incompressible steel mandril a filling of 

 pitch and resin; the number of rolls may be diminished, or tho designs on the 

 concave surface of the rollers may be varied according to the style of ornament 

 .desired. It is unnecessary to state that the rollers are formed of the best steel, and 

 are carefully tempered after the die-sinker has cut the design thereon. 



When the ornamentation desired consists of series of reeds or flutes traversing 

 spirally and screw-like, familiarly known as ' twisted tube,' and largely used in the 

 construction of mediaeval and other gas-fittings, &c., the tool represents a screw-nut, 



