For the three still interested
it appears (about) 24 is the most common
Engines Of War: or, Historical and Experimental Observations on Ancient And Modern Warlike Machines And Implements, Including the Manufacture of Guns, Gunpowder, and Swords with remarks on Bronze, Iron, Steel, &c. Henry Wilkinson, M.R.A.S. London 1841
p. 70 Part III On The Manufacture of Fire-Arms, And Modern Improvements.
http://books.google.com/books?id=0XJeF_oa3SMC The iron called Damascus, from it’s resemblance to the celebrated Oriental barrels and sword blades, is now manufactured in great perfection in this country, as well as in France and Germany, and may be varied in fineness or pattern to almost any extent, according to the various manipulations it may undergo. One method is to unite, by welding
25 bars of iron and mild steel alternately, each about 2 feet long, 2 inches wide, and 1/4 of an inch thick; and having drawn the whole mass into a long bar, or rod, 3/8 of an inch square, it is then cut into proper lengths of from five to six feet; one of these pieces being made red hot is held firmly in a vice, or in a square hole, to prevent it from turning, while the other end is twisted by a brace, or by machinery, taking care that the turns are regular, and holding those parts which turn closer than others with a pair of tongs, the rod is by this means shortened to half it’s original length, and made quite round.
1851 Great Exhibition of the Industry of all Nations: Official Cataloguehttp://www.gracesguide.co.uk/1851_Great_Exhibition:_Official_Catalogue
Class VIII. Naval Architecture, Military Engineering, Guns, Weapons, etc.
200. WILKINSON & SON, 27 Pall Mall — Manufacturers.
A series of illustrations, showing the different stages of the manufacture of gun-barrels:
(A.) Horse-shoe nails, or stubs.
(B.) Old coach-springs, cut up by means of shears.
(C.) Scrap stub-iron.
(D.) A gun-barrel in its various stages, made of a mixture of stubs and steel (A. and D.), first twisted into a spiral, then partially welded by jumping, then completely welded, and the figure of the iron brought out by acids.
(E.) A bar of iron made from scrap (C), for Damascus twist.
(F.) A bar of steel, made from scrap (D.), for Damascus twist.
(G.)
Twenty-one bars of iron and steel (E. and F.), packed alternately for welding
(H.) Twenty-one bars (G.) welded together.
(I.) A square rod made by drawing out the mass (H.) between rollers.
(J.) The square rod (I.) twisted round its own axis, and then flattened, showing the figure produced.
(K.) Specimen to show the manner in which the figure called Damascus twist is produced; two bars or rods (I.), are first twisted round their axis the whole length, the one to the right and the other to the left, then flattened and welded together, then twisted spirally to form the barrel as in (D.), partially welded by jumping, and the welding completed, filed at the end, and the figure produced.
(L.) A similar specimen, finer; composed of
two bars of 48 alternations of iron and steel.
(M.) A similar specimen, composed of three smaller bars of
21 alternations.
(N.) A similar specimen, called "chain twist."
(O.) A similar specimen, called "steel Damascus."
(P.) A finished barrel, composed of seven different kinds of twist.
The Irish Industrial Exhibition of 1853: A Detailed Catalogue of Its Contents John Sproule 1854
http://books.google.com/books?id=cNKl8YYZejsC The process of making Damascus barrels is more complicated, as involving a greater number of stages. The strand in this case is composed of three or four twisted rods instead of two, and they are all generally twisted in one direction; but it is in the manufacture of the rods themselves that the essential difference consists. These are no longer stub iron or decarbonized steel, but are formed of from
twenty to four-and-twenty alternate layers of iron and steel welded together.
The New American Cyclopaedia: A Popular Dictionary of General Knowledge George Ripley, Charles Anderson Dana 1859
http://books.google.com/books?id=kL9PAAAAMAAJ Greener describes the most perfect work of this kind as being done at Liege, Belgium.
Alternate bars of iron and steel, 32 of each, are piled and rolled into a sheet 3/16 of an inch thick; this is then slit into 3 square rods, which are twisted till the lines resemble the threads of a fine screw, and 6 of these are placed together and welded into one. The figure produced is exceedingly fine…
Appleton's Dictionary of Machines, Mechanics, Engine-work, and Engineering, 1873
http://books.google.com/books?id=zi5VAAAAMAAJ Gun Barrels
http://books.google.com/books?id=zi5VAAAAMAAJ&pg=PA936&dq The iron called Damascus from its resemblance to the celebrated Oriental barrels and sword-blades, is now manufactured by welding
25 bars of iron and mild steel alternately, each about 2 feet long, 2 inches wide, and 1/4 of an inch thick…
