Drill rods made of high carbon steel are used to make various tools and bearings. They come in different diameters and can be water or oil-hardened. Water-hardened rods are easier to work with but not suitable for welding, while oil-hardened rods are tougher and can be welded. Hardening is done by heating and cooling the rods in water or oil. Tempering reduces the hardness and makes the steel more workable. Cooling should be done slowly to prevent warping.
A drill rod is made of very high carbon steel and is used to make drill bits, taps, dowel pins and roller bearings. A drill rod is also used in the manufacture of hammers, files and punches. The level of carbon used in making steel determines its hardness. Drill rod is sold in lengths typically 36 inches (91 cm) long and in diameters ranging from 1/16 inch (1.5 mm) to 2 inches (5 cm) or larger. The rod can also be produced in a square design.
There are two basic types of drill rods: water-hardened and oil-hardened. A water hardened rod is used in making hammers and files as the rod is not strongly bonded. This allows the material to be worked more easily than oil-hardened drill rod, although water-hardened drill rod is not suitable for welding. On the other hand, the oil-hardened rod is easily welded and machined, it is suitable for general tool making due to its long-lasting toughness.
In the water hardening process, the rod is heated to a cherry red color and then immersed in a tub of water and allowed to cool. This creates a tough, durable product that is still easily worked. When the rod is heated to a cherry red color and then dipped in hot oil, the surface becomes extremely hard and will damage most cutting tools. Therefore, these rods must have all of their machining finished before curing in oil.
Depending on the intended use, some bars must be hardened before machining. To temper steel, it must be heated slowly after it has been hardened with water or oil. By heating the steel to about 800 degrees Fahrenheit (426 degrees Celsius), the hardness is slightly reduced and the steel is more workable. Once brought up to temperature, the steel is left to cool in the air. Once cooled, the piece can be polished.
The difference in hardening from water and oil is that water is a much better conductor of heat and cools the rod faster. Parts should not be agitated in the water as this promotes much faster cooling on the side of the tool being pushed through the coolant. This can cause warping as the sides cool at different rates. This is critical when creating precision work pieces. When making a knife, the steel only needs to be hardened in a vertical up and down motion.
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