Drill bit sizes

Drill bits are the cutting tools of drilling machines. They can be made in any size to order, but standards organizations have defined sets of sizes that are produced routinely by drill bit manufacturers and stocked by distributors. Drill bits are the cutting tools of drilling machines. They can be made in any size to order, but standards organizations have defined sets of sizes that are produced routinely by drill bit manufacturers and stocked by distributors. In the U.S., fractional inch and gauge drill bit sizes are in common use. In nearly all other countries, metric drill bit sizes are most common, and all others are anachronisms or are reserved for dealing with designs from the US. The British Standards on replacing gauge size drill bits with metric sizes in the UK was first published in 1959. A comprehensive table for metric, fractional wire and tapping sizes can be found at the drill and tap size chart. Metric drill bit sizes define the diameter of the bit in terms of standard metric lengths. Standards organizations define sets of sizes that are conventionally manufactured and stocked. For example, British Standard BS 328 defines sizes from 0.2 mm to 25.0 mm. From 0.2 through 0.98 mm, sizes are defined as follows, where N is an integer from 2 through 9: From 1.0 through 2.95 mm, sizes are defined as follows, where N is an integer from 10 through 29: From 3.0 through 13.9 mm, sizes are defined as follows, where N is an integer from 30 through 139: From 14.0 through 25.0 mm, sizes are defined as follows, where M is an integer from 14 through 25: