Admiralty

The Admiralty Tests for iron for ship-building may be tabulated as follows : -

BB or 1st class plate iron and sheet iron 1/4 inch thick and above . .

(grain lengthways)..

Tensile Strain per square inch.

22 tons.

(grain crossways)..

18 „

Do., boiler plate, do. do.

(grain lengthways)..

• 21 „

(grain crossways)..

• 18 „

B or second class plate and sheet iron . •

(grain lengthways)....

. 20 „

(grain crossways)..

17 ,,

Angle, Bulb, T, Angle-bulb, Tee-bulb, or other iron of ordinary form ..

(grain lengthways)..

22 „

All the above are in addition to the forge tests enumerated at page 281...

BB bar iron, moulding, sash bar, half round, and segmental iron. Fire-bar iron ..

Do. ... 22 „ and such forge tests, hot and cold, as may be deemed expedient.

Rough Tests For Wrought Iron

There are several very useful tests which may be applied to iron of different forms in addition to the tensile tests.

Forge Tests

Plate iron may be bent either hot or cold, with or across the grain. The bending is done upon a cast-iron rectangular slab, having the corner slightly rounded off. The angle through xchich the plate should lend without cracking depends upon the quality and thickness of the iron, and is shown in the following tables, which, together with the tests following for angle irons, etc., have been extracted from the Admiralty directions for test-

PLATE IRON.

Hot.

Cold.

Thickness.

1 inch thick and under.

1 inch.

3/4 inch.

1/2 inch.

1/4 inch.

B B, grain lengthways .

125°

15°

25°

35°

70°

„ „ cross-ways

90°

10°

15°

30°

B, grain lengthways

90°

10°

20°

30°

65°

:, „ crossways ....

60°

10°

20°

SHEET IRON.

Hot.

Cold.

B B, grain lengthways .....

125°

90°

„ „ crossways...

90°

40°

B, grain lengthways....

90°

75°

„ „ crossways ....

60°

30°

N.B. - It should be noticed that the angle mentioned above in each case is the angle through which the plate is bent, commencing at the horizontal, not the angle between the two sides of the plate after it is bent.