Chicago-Latrobe 44091 #21 118° Jobber Length Drill Bit

Chicago-Latrobe 44091 #21 Jobber Drill Bit

The Chicago-Latrobe 44091 is a #21 jobber length drill bit made from high speed steel with a black oxide finish. It features a conventional 118 degree point angle and a decimal equivalent of .1590 inches. This general purpose bit suits maintenance professionals and metalworkers drilling wire gauge holes in steel and similar materials. It is not designed for coolant-through applications or specialised coated performance.

Thermals noise and power draw in normal use

The high speed steel construction manages heat effectively during standard drilling in mild steel and non-ferrous metals. Black oxide coating helps reduce friction and chip welding at typical hand-fed speeds. No coolant holes are present, so the bit relies on external lubrication or peck drilling to control temperature. Noise and vibration remain consistent with conventional jobber geometry in portable drills.

Behaviour under sustained load

Under continuous drilling the conventional 118 degree point maintains centring but generates more thrust than split point designs. The absence of coolant holes limits heat evacuation in deep holes, requiring frequent withdrawal to clear chips and prevent annealing. Black oxide surface treatment resists galling longer than bright finish bits, yet extended high speed runs will dull the cutting edges faster than cobalt or carbide alternatives.