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Metric Specifications


More and more Metric specifications are showing up on manufacturing prints in the USA. To help clarify abbreviations we offer explanations below:

ASME/USCTI: USA Tool Standards

American Society of Mechanical Engineering / United States Cutting Tool Institute, all standards are specified in the Imperial measurement (Inches).

DIN: German Standard

Deutsches Institut Fur Normung / German Institute for Standard, all measurements are to the Metric system.

JIS: Japanese Standard

Japanese Industrial Standard, all measurements are to the metric system

ISO: Global

International Standardization Organization, all measurements are to the metric system.

Other countries have their own standards that would relate to specific industries like aircraft and automotive applications. By way of example, in the USA other standards like NAS – National Aero Space. SAE – Society of Automotive Engineers are related to specific of industries.

Here are some examples of differences in Metric Jobber Drills versus an Inch
Jobber Drill:

  1. A metric drill OAL is measured from back of shank to point tip of the drill; an inch drill is measured from back of shank to point shoulder.
  2. OAL on a standard jobber DIN drill (specified as DIN 338) can be shorter than an Inch jobber drill. You need to be vigilant when specifying because DIN Flute lengths are a lot shorter and if using an inch drill bushing your flutes could still be inside the bushing preventing chips from being evacuated.
  3. Metric Drill OD tolerances are measured in lower case letters such as h8. Inch sizes, on the other hand, would be +. 0 to a minus tolerance.
  4. Metric tangs are also different and will not fit into an inch collet.