There are three different peripheral grinds available on a gundrill tip.

The most common is our #101 grind, used for most deep hole drills, in which the wear land is relieved 175 degrees from the cutting edge. This provides for the freest cutting scenario and results in the longest tool life. The finished tip is not micable. Backtaper is .0008-.001" per inch to prevent drill binding and reduce tool wear. Straightness of .001" per inch runout is possible, and size will be within .0005" overall. Finish will be 80 micro inches or less.

When closer hole tolerance is required, we employ our #102 grind, in which the wear land is relieved 185 degrees from the cutting edge, and Backtaper is reduced to .0002-.0005" per inch, with runout reduced to as little as .0002" per inch. Surface finish improves to 30 micro inches or less.

In special applications, our #103 grind adds a third wear pad at the trailing edge of the tip. This provides for maximum stability of the drill and the smoothest finish (as low as four micro inches) in the hole, due to the increased burnishing effect of the third wearpad. Drill life is shortened, however due to the increased heat generated. All of the above tolerances are of course dependent on numerous variables, including the material, the setup, and the machining parameters.

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