31 OF ENGINEERING FORMULAE.
Tests ok Iron. (Indian Store Department.)
Material. J Ultimate Stress. Tons per sq. in. Contraction pör cent, of area at fracture-
Highest Class. Lowest Class. Highest Class. Lowest Class.
Bars, round & square. 27 23 45 20
Do. flat 26 22 40 16
Angle or T • ■ • • 25 21 30 12
Plate lengthways .. 24 20 20 8
Do. crossways .. 22 17 12 3
Materials tested to 4 per cent, of total value.
Materials under specified strain are accepted if the contrac-
tion is proportionally higher.
Admiralty Tests fok Ikon Plate.
Hot, to bend without fracture from 90° to 125°.
Cold Test, to beud without fracture to the following
angles:—
Lengthways. Crossways.
1 in. plate..........10° to 15° 5°
| „ ..........20° „ 25° 5° to 10°
i „ ..........30° „ 35° 10° „ 15°
I „ __________55° „ 70° 20° „ 30°
Tests fob Cast Ibon.
A common test for cast iron is 1 ton on the centre of an
inch square bar 1 foot between supports; or 30 cwt. on the
centre of a bar 2 inches deep X 1 inch wide and 3 feet between
supports—the bar to bear the load without breaking.
Tükneb’s Scale pok Steel,
T. contains from 1 • 65 to 1 -40 carbon.
II. „ V40„l-15 „
III. „ 1-15 „0'90 „
IV. „ -90 „ -65 „
V. „ -65 „ -40 „
VI. „ ’40 „ -15 „ ■
VH. „ ’15 „ -0 „