Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 417
butt-welded or lap-welded. It is a mere question of manufacture. It is difficult to make a lap-welded tube less than 1^ diameter, and therefore below this size they are usually butt-welded; but this size and above, lap-welded. Wrought-iron j^ipes of the smaller diameters are connected by… … Fig. 943.
Mechanical drawing
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