i, = melting and foundry loss (all metal unaccounted for) in percentage of the total metal charged. This 
percentage is obtained from the average cost summary and it is item 40 on the sample copy for 
illustrative purposes on page 19. L is 10.00% in this summary. 
3 — slagged castings in percentage of the total metal charged. It is item 38 on page 19. Bis 0.3% in this 
illustration. 
D = weight of defective castings in pounds. The weight of a defective casting is the same as the shipping 
weight of a good casting. This weight is 600 pounds for the sample casting whose cost calcula- 
tion is illustrated on page 25. 
d — weight of heads and gates used on both the good and the defective castings, in pounds. This weight is 
(800 pounds for the sample casting whose cost calculation is illustrated on page 25. 
The formula used for calculating the yield of a specific casting or castings made from a specific pattern 
san be stated in simple terms making it more easily understood. The yield is calculated by multiplying the 
shipping weight of the casting or castings (G in the formula) by the difference between 100% and the sum 
>f the average percentages for metal losses (S), melting and foundry loss (L), and slagged castings (B). 
This result is then divided by the sum of the weights of the good castings (G), the defective castings (D), 
and the heads and gates used on both the good and the defective castings (H), which gives the yield. 
In the above formula, the terms S, L, and B are constant as they represent average figures taken from 
‘he average cost summary representing average or normal operations of the foundry. The other terms vary 
with the casting whose cost is to be determined. By substituting the proper figures for the letters in the above 
formula, the yield for the casting illustrated on page 23, is calculated to be 48.2%. The use of this simple 
method for determining the yield for a specific casting is illustrated later on page 23. 
The cost of steel per net ton of good castings varies with the yield, and it includes two main items: 
the cost of metals (item 1 on page 18), and the conversion or melting cost. The cost of metals should be based 
on the market prices of the metals used for making the steel. The conversion or melting cost (this is item 2 
‘ess item 1 on the average cost summary, page 18) should be the average cost representing average or normal 
yperations in the foundry. This average conversion cost should always be used instead of the actual conver- 
sion cost for any single month. It is calculated in the following manner by using for this illustration the as- 
sumed figures on the average cost summary on page 18: 
Average Amount Prevailing Cost Per Net 
Per Net Ton of Charge Cost Per Unit Ton of Charge 
.... 6 man hours 7oc an hour...........$ 4.20 
60 gallons 6c a gallon........... 3.60 
1.00 
90 
.40 
labor LL... 
Fuel ......ovoonnt. 
Supplies ........... 
furnace Repairs ................ 
“ther Repairs in Metal Department. . 
Total average conversion cost per net ton charged. .$10.10 
[nn calculating the average conversion cost for electric furnaces the average kilowatt hours and pounds of elec- 
rodes per net ton of charge would be used in the manner illustrated above. Also the average cost per kilowatt- 
Jour representing average operating conditions should be used. 
To obtain the cost of steel for a specific casting, its yield is calculated from the formula given above, 
nd the cost of steel can then be quickly calculated from the following formula: 
} 100 M — [P Xx (100 —L)] 
Cost of steel per net ton of good castings =— - -LP 
M = total metals and conversion cost per net ton of metal charged into the furnace. It is item 2 on the sam- 
ple copy of an average cost summary illustrated on page 18, which should be adjusted with the 
market prices of metals. _ 
., = melting and foundry loss (all metal unaccounted for) in percentage of total metal charged into the fur- 
nace. Tt is item 40 on the sample copy of an average cost summary illustrated on page 10.