Weight on bit Weight on bit Weight on bit (WOB), as expressed in the oil industry, is the amount of downward force exerted on the drill bit and is normally measured in thousands of pounds. Weight on bit is provided by drill collars, which are thick-walled tubular pieces machined from solid bars of steel, usually plain carbon steel but sometimes of nonmagnetic nickel-copper alloy or other nonmagnetic premium alloys. Gravity acts on the large mass of the collars to provide the downward force needed for the bits to efficiently break rock. To accurately control the amount of force applied to the bit, the
Isotopes of curium in the periodic table. The shortest-lived isomer is Cm with a half-life of 34 milliseconds. Isotopes of curium Curium (Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was Cm in 1944, which has 146 neutrons. There are 21 known radioisotopes with atomic masses ranging from Cm to Cm. There are also four known nuclear isomers (Cm, Cm, Cm, and Cm). The longest-lived isotope is Cm, with a half-life of 15.6 million years – several