Net Cost of Extrusions Less than Bar Stock

Depending upon the steel grade, the difference in final cost between an extrusion and a part made by machining can be enlightening. Look at the part depicted below made from grade 304 stainless steel.

the finished extruded shape weighs 9 pounds per foot. To machine this part from a rectangular bar would require a bar 1.750" X 5.000". This bar would weigh 27 pounds per foot. Thus to machine this part one foot long would require the purchase of 27 pounds of material. In this instance, you not only pay more initially, you pay for the cost of 18 pounds of surplus material, the cost to machine this surplus material, and the cost of inbound freight. Suppose the finished job required 4,000 feet of finished material. The 9 pound extrusion would require one truckload of raw material. The bar stock would require three truckloads of material. In this instance, you pay for two truckloads of material that is machined into chips and the surplus is scrapped. What are your machining costs per pound of metal removal? Remember, you must machine away 18 pounds of stock.