Gun Drill - 1: Drilling Deep
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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.
For the machinist deep hole drilling with the standard twist drill can have a variety of problems:
  • The deeper the hole the more the drill may deviate or curve
  • The drill must be retracted continuously for chip removal and coolant application
  • Deep close tolerance holes using standard twist drill often require more than one drill to rough out the bore then a reaming or a boring tool to complete the operation
To overcome this problem high-pressure coolant drills and gun-drills were designed that can machine a precision bore in one pass. This is accomplished by coolant which is forced over the diameter of the tool via a passage inside the drill. The pressure of the coolant then forces the chips back out of the drill either through the relief between flutes, a channel, or through the tubular shank. Deep hole drilling machines are often called "gun drills" because the production of cannon was their original use and they are still used to day to drill out rifle barrels.
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