on steel around a spot which has been overstrained. These lines show where the excessive stress produced by hammering broke off the scale, forming bright lines here indicated in black, and which are of perfectly regular spiral form which it is not difficult to follow. This straightening was done with the greatest care and precaution, and no trouble spared to do a good job, and still-see the result! Is it to be wondered at that incompetent men will ruin a steel fabrication, or that some "engineers" say that steel is unfit as a material of construction. But there is a remedy for all this, which must be plain to all, and can be best expressed by the old proverb, " Prevention is better than cure." Start the work correctly in the first place, use nothing but straight shapes, and condemn all abuse and carelessness, however slight, and half the battle is won; but let the bad practices once obtain for ever so short a time and it will be impossible to break them. These remarks and tests tend to show several things in regard to fabrication of steel work, namely: "Steel eye-bars can be made perfect in every respect, much superior to those of iron; and methods used in shops at the present time must at an early day be superseded by such as will insure better work." An additional point of the greatest importance is this; with current prices of labor and material, not only in Pittsburgh, but in Eastern shops as well, steel work is a little cheaper than iron for all large structures. The ultimate strength of steel, such as is commonly used for structural purposes, is to that of iron as 100: 71, or as 100: 65 when comparing the elastic limits, while the relative cost of steel to iron, as taken from contract prices obtaining at present is as 100:74. Thus basing all calculations of parts on the elastic limit of the material and the cost on current prices, the relative cost of an iron and steel structure for the same work, will be as : 100 85.8: 100, not considering a smaller freight account, there being less material in the work; nor cheaper erection, work being less cumbersome. 65 = TENSILE TESTS OF STEEL EYE-BARS. BY GUS. C. HENNING, M.E. WATERTOWN ARSENAL, MASS., Report of Mechanical Tests made with the 400 ton U. S. Testing Machine. Elongation of pin holes M1 = 0.75"; M2 = 1.08". Elongation of ten sections (2.79" fractured section) 1.69"; 1.65; 1.68; 1.60; 1.91; 1.65; 1.59; 1.48; 1.51; 1.59; 1.55; 1.60; 1.60; 1.55; 1.58; 1.54; 1.50; 1.53; 1.62. Area at fracture, 5.33 × 0.79 = 4.21 in. Reduction 33.7%. Fractured 16" from centre of pin hole M. Appearance of fracture silky centre with fine granular metal at sides radiating from centre. The thickening of metal in front of pin hole M, and dishing of the heads was such that the under side of the head was flat after the test. Head M, was dished concave on the under side; placing an 18" straight edge along the axis of the bar, showed an opening of the metal at the front side of the pin hole 0.25", and at the back side of the pin hole of 0.08". = Test No. 4583. Sectional Area, 6.33 = '';-Gauged Length, 160". |