(b) Chemical Composition.- To comply with  Regulation 33 (b).

(c) Freedom from Defects.- The finished tubes, both externally and internally shall be sound, clean, smooth, well finished and free from surface defects and longitudinal grooving, and the ends must be clean and square.

(d) Tolerance.- The actual weight of each tube shall not be more than 5% above the calculated weight. Unless, otherwise specified, they shall be straight cylindrical, of uniform thickness and external diameter throughout.

(e) Tensile Tests.- Tensile tests shall be made on pieces of tubes or strips cut from the tube. If the tensile test is made on a piece of tube, the ultimate tensile stress shall be not less than 14.50 tons (32,480 lbs.) per sq. inch with an elongation of not less than 50 per cent on 2 inches.

If the tensile test is made on strip cut from the tube, the ultimate tensile stress shall be not less than 14 tons (31,360 lbs.) per sq. inch with an elongation of not less than 40 per cent on a test piece having a gauge length of four times the square root of the area.

The results obtained from a batch shall be uniform, and should a variation of more than one ton (2,240 lbs.) per sq. inch be found between any number of tubes tested, the batch shall be liable to rejection. A batch shall not consist of more than 500 tubes.

(f) Bulging or Drifting Test.- The test piece shall stand bulging or drifting cold (see Diagrams 1 and 2 respectively) without showing either crack or flaw, until, the outside diameter of the bulged or drifted end measures not less than 25 per cent more than the original diameter of the tube.

(g) Flanging Test.- The test piece shall stand flanging cold (see Diagram 3) without showing either crack or flaw until the diameter of the flange measures not less than 40 per cent more than the original diameter of the tube.

(h) Flattening and Doubling over Test.- The test piece shall stand the following test, both cold and at a red heat, without showing either crack or flaw. The test piece shall be flattened down until the interior surfaces of the tube meet and then be doubled over on itself, that is bend through an angle of 180° (see Diagram 4) the bend being at right angles to the direction of the length of the tube.

The tubes shall withstand the test without showing any signs of weeping or any evidence of defects.

(j) Treatment of Test Specimens.- All test material, if not already in an annealed condition, shall be annealed before testing and shall comply with the mechanical tests without further heat or mechanical treatment.