Letter Sizes Drill Bits. The numbered sizes are based on but unfortunately are not identical to the stubs steel wire gauge, which originated in 19th century great britain. 1/16 and larger have a 135 degree split point.
The numbered sizes are based on but unfortunately are not identical to the stubs steel wire gauge, which originated in 19th century great britain. 1/16 and larger have a 135 degree split point. They are commonly used to drill lathe centres and spotting drills, i.e.marking holes to guide twist drilling.
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1/16 and larger have a 135 degree split point. Drill number / decimal cross reference drill number decimal (inch) decimal (mm) 97.0059.150 96.0063.160 95.0067.170 94.0071.180 93.0075.190 92.0079.200 91. This type of drill is used in high tensile material such as stainless and titanium. In practice, you will seldom see number sizes past #80.