Machinery's Handbook - Properties of the Steel
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.

The blueprint shows that the part to be machined is 4130 steel and has been tempered at 800 degrees. There will be a need to determine the tensile strength of the material so that the appropriate cutting tool can be chosen. Also the handbook will be used to find and check the hardness to the metal* using a Rockwell C scale tester.

First, locate the chapter for the Properties, Treatment, and Testing of Materials.

Then look for steels and read the tensile strength of 4130 tempered at 800 degrees from the table: 186,000 Pounds per Square Inch.

To find the hardness of the material on the Rockwell C scale, first note that its Brinell hardness is 380. Now turn to another table in the handbook that converts Brinell to Rockwell C scale. Once it is noted that the hardness is 41 RC it becomes apparent that a high speed steel cutter is not appropriate. A coated carbide cutter is more suitable.

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