MISCELLANEOUS METALS. 619 



Have at least one upper and lower shoe of each kind assembled and make sure that there is 



no interference. 



(24) Make sure that iron templets used for reaming are properly set and held to line. 



(25) Secure match-marking diagrams for work which has been assembled and reamed and 

 m. ike sure that tin- match marks are plainly visible. 



(26) Have proper camber blocking used in assembling trusses and secure the desired camber 

 lu-furr tin- reaming is done. 



(27) Require that all treads and supports for the drums of draw spans be carefully leveled 

 with an instrument. 



(28) Study carefully the machine details and discriminate between those dimensions which 

 must be exact and those in which slight variations are permissible. 



1 >et ermine in advance the desired accuracy of driving fits for bolts or keys and similar parts 

 and make sure that such accuracy is attained. 



(29) Examine castings carefully for blowholes and other imperfections and discriminate 

 between such defects as are unimportant and those which render the castings unfit for use. 



(30) Make sure that bushings, collars and similar parts are held securely in place. 



(31) Make sure that all drum wheels, expansion rollers, turntable rollers and similar parts 

 are exact in size, so as to carry equally the loads which may be placed upon them. 



(32) Ascertain in advance 'that the paint provided complies with specifications. Watch 

 carefully the painting directions and make sure that paint is properly applied and only where 

 intended. 



(33) Verify all shop marks and make sure that they are legible as well as correct. 



(34) Have important members so loaded as to be headed in the right direction upon arrival 

 at the site of the work. 



(35) Try a few countersunk head bolts in the holes where they are to be used to insure a 

 proper fit. 



(36) Make sure that small pieces are bolted in place for shipment as shown on the plans and 

 that other small parts are properly boxed or otherwise secured against loss. 



(37) Make sure that rivets, tie rods, anchor bolts and miscellaneous parts are shipped so as 

 to avoid delay in erection. 



(38) Examine the field rivets to insure that they are free from fins or other defects. 



(39) Exercise special care in the examination of all movable structures and particularly their 

 moving parts. 



(40) Make reports weekly or as directed, exhibiting carefully and concisely the actual con- 

 ditions. 



(41) Observe carefully and report such unusual difficulties as may be encountered and the 

 means adopted in overcoming them, and endeavor by a study of the details or other means to 

 make recommendations which will prevent their recurrence in future work. 



MISCELLANEOUS METALS. The physical properties of the following metals depend 

 upon whether they are cast, rolled, or drawn, and upon the details of manufacture, and the values 

 given are therefore approximate. 



Aluminum has a specific gravity of 2.58 to 2.7. The ultimate tensile strength per sq. in. is 

 about 15,000 Ib. for cast, 24,000 Ib. for sheet, and 30,000 to 65,000 Ib. for aluminum wire. The 

 elastic limit is about i the ultimate strength. The modulus of elasticity is about 11,000,000 Ib. 

 per sq. in. Aluminum is used in engineering construction principally in the form of an alloy. 



Copper has a specific gravity of 8.6 to 8.9. The ultimate tensile strength varies from 36,000 

 to 40,000 Ib. per sq. in. for soft copper wire with an elongation in 10 in. of 35 to 20 per cent; to 

 49,000 to 67,000 Ib. per sq. in. for hard-drawn copper wire with an elongation varying from 3.75 

 per cent in 10 in., to an elongation of 0.85 per cent in 60 in. Copper is also used in an alloy with 

 other metals. 



Zinc, or spelter, has a specific gravity of about 7.00. The ultimate tensile strength per sq. in. 

 varies from 3000 to 8000 Ib. It is used for galvanizing and for making alloys. 



Nickel has a specific gravity of about 8.8. Nickel is used principally in alloys. 



Tin has a specific gravity of about 7.35. Tin is used as a covering for iron and steel sheets and 

 in alloys. 



Lead has a specific gravity of about 11.4. Lead is very plastic and flows easily under stress. 



ALLOYS. An alloy is a combination of two or more metals made by mixing them when in a 

 molten condition. Alloys are commonly mechanical mixtures; although some have a slight chem- 

 ical union. The properties of alloys depend not only upon the ingredients, but upon the method and 



