These robust Boring Bars are perfect for most deep boring chores on your lathe. They are double-ended and hold square bits at 90deg or at 45deg. Comes with a wrench and tool bit Square holder. It is suitable for general purpose applications and can be used on iron, steel, aluminum, brass, copper and wood. Boring bars are used to enlarge or finish the inside diameter of a work piece.

During the tempering process, the carbon atoms move out of the spaces between the iron atoms in the martensite to form the iron carbide particles. The strain within the martensite is relieved as the carbon atoms move out from between the iron atoms in the martensite. This results in an improvement in the steel toughness, at the expense of reduced strength.

Imagine you’re a warrior during the middle ages and it’s time to get a new sword. So, you go to a blacksmith and buy a sharp, shiny long sword. A few weeks later you’re in a battle, fighting at the front of the shield wall. You take a huge swing at the enemy, who meets your blow with his sword, and your sword shatters into several pieces. Unfortunately for you, your blacksmith outsourced a batch of swords to a blacksmith on the other side of town who didn’t have time to temper the swords. As a result, the swords were strong, but brittle. Their lack of toughness meant that they could not absorb much of an impact before fracturing.

Item Code No. SetBar Size Dia.Bar Size LengthHolder Size LengthHolder Size SquareSquare Bit Size ABM-IMT-61003/8”4-1/2”2-1/8”1/2”1/8” ABM-IMT-61017/16”5-1/4”2-1/2”5/8”3/16” ABM-IMT-61029/16”6-3/4”3”3/4”1/4” ABM-IMT-61033/4”9”3-3/4”1”5/16” ABM-IMT-61047/8”11-1/2”4-1/2”1-1/8”3/8” ABM-IMT-61051-1/8”14”5”1-3/8”7/16” ABM-IMT-61061-1/4”15”5-1/4”1-5/8”1/2” ABM-IMT-61071-3/8”16”6”1-3/4”5/8” ABM-IMT-61081-1/2”18”6”2”3/4” ABM-IMT-61092”20”7”3”1”

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The amount of tempering required depends on the particular application in which the steel will be used. In some cases, toughness is not important, so tempering at a low temperature for a short period of time is acceptable. In cases where very strong and tough steel is required a high carbon steel tempered at a high temperature might be used.

Tempering steel after quenching is part of the through hardening heat treatment. The purpose of tempering is to improve steel toughness.

Purchase our Principles of Metallurgy online course for only $59. It's normally $225. Use discount code POM59 in the checkout. Available to the first 25 customers.

Tempering is used to improve toughness in steel that has been through hardened by heating it to form austenite and then quenching it to form martensite. During the tempering process the steel is heated to a temperature between 125 °C (255°F) and 700 °C (1,292 °F). At these temperatures the martensite decomposes, initially forming iron carbide particles. The higher the temperature, the faster the decomposition for any given period of time. The micrograph shows a steel after substantial tempering. The black particles are iron carbide.

Untempered martensite is a strong, hard, brittle material. The stronger and harder it is, the more brittle it is. The strength and hardness is a due to elastic strains within the martensite, a result of too many carbon atoms being in the spaces between the iron atoms in the martensite. As the amount of carbon in a steel increases (up to about 0.8 weight percent carbon) the martensite strength and hardness increases.

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• Double Ended one piece boring bars have 90° & 45° square ends.• Set Supplied with Boring Bar, Holder, Allen Key and Screw.• Tool Bits also available on extra cost.• Shiny black finish.• Available with and without Holders.• Only Holder and only Boring Bar also available separately.• Single Ended Boring Bars also available.

Learn more about about tempering steel and steel heat treating is in our Steel Metallurgy and Steel Through Hardening courses. The book Steels: Processing, Structure, and Performance by George Krauss provides a comprehensive discussion of steel heat treating.