Drill Specifications

More different specifications are showing up in manufacturing prints in the USA. To help clarify abbreviations see the explanations below.

Other countries have their own standards that would relate to specific products such as aircraft and automotive. In the USA other standards, including NAS (National Aero Space) and SAE (Society of Automotive Engineers), are related to those types of industries. Here are some examples of differences in metric jobber drills versus inch jobber drills.

  1. A metric drill OAL is measured from back of shank to point tip; an inch drill is measured from back of shank to point shoulder.
  2. OAL and flute length of a standard DIN 338 jobber drill can be shorter than an inch jobber drill. The flute length in parparticular should be noted when using an inch drill bushing. The shorter flutes could end inside the bushing, preventing chip evacuation.
  3. Metric drill OD tolerances are measured in lower case letters such as h8; inch sizes would be +. 0 to a minus tolerance.
  4. Metric tangs are sized differently and will not fit into an inch collet.