Seamless Steel Savings Illustrated

As an illustration of the possible cost savings, take a hypothetical example of a gear application that requires 8620 steel ,vith dimensions of 6.435 inches outer diameter (OD) by 3.200 inches inner diameter (ID) before hobbing and broaching. The manufacturer needs 400 feet of metal to produce 500 gears. (Yardstick measurement: About 50 percent material has to be removed to result in 3.200-inch ID in 6.435-inch OD bar.)

The alternatives are to buy 6V2- inch round bar, or to buy seamless tubing that has a 6 V2-inch OD by 3-inch ID. The bar weighs ll2.8 pounds per foot, and costs $49.52 per foot. * The cost of machine time to bore the ID is $21. 60 per foot. Total cost: $71. 12. But the allowance for scrap value of the 3-inch bored ID is 5 cents per pound, or $1. 20 per foot. This adjusts the total cost of bar to $69.92 per foot. The tubing weighs 88.78 pounds per foot, and its cost is $58. 73 per foot. The difference between the $69.92 total adjusted cost of the barand the $58. 73 cost of the seamless tube is $11. 19- which represents a 16 percent cost savings possible with the use of tubing instead of using bar starting stock.

It is important to note that the calculations include the cost of machining the ID hole in the bar stock.