Twist drill bits are available in standard lengths, referred to as Stub-length or Screw-Machine-length (short), the extremely common Jobber-length (medium), and Taper-length or Long-Series (long).

While longer bits can drill deeper holes, they are more flexible meaning that the holes they drill may have an inaccurate location or wander from the intended axis. The functional length of a bit determines how deep a hole can be drilled, and also determines the stiffness of the bit and accuracy of the resultant hole.A very acute point angle has more web surface area presented to the work at any one time, requiring an aggressive lip angle, where a flat bit is extremely sensitive to small changes in lip angle due to the small surface area supporting the cutting edges. The proper amount of lip clearance is determined by the point angle. Both conditions can cause binding, wear, and eventual catastrophic failure of the tool. A greater lip angle will cause the bit to cut more aggressively under the same amount of point pressure as a bit with a smaller lip angle. The lip angle determines the amount of support provided to the cutting edge.The correct point angle for the hardness of the material influences wandering, chatter, hole shape, and wear rate. Harder materials require a larger point angle, and softer materials require a sharper angle. The point angle, or the angle formed at the tip of the bit, is determined by the material the bit will be operating in.Low spiral (low twist rate or 'elongated flute') drill bits are used in cutting applications where high cutting speeds are traditionally used, and where the material has a tendency to gall on the bit or otherwise clog the hole, such as aluminum or copper. A fast spiral (high twist rate or 'compact flute') drill bit is used in high feed rate applications under low spindle speeds, where removal of a large volume of chips is required. The spiral (or rate of twist) in the drill bit controls the rate of chip removal.Characteristics ĭrill geometry has several characteristics: There are also certain specialized drill bits that can create holes with a non-circular cross-section. A comprehensive drill bit and tap size chart lists metric and imperial sized drills alongside the required screw tap sizes. The drill will grasp the upper end of a bit called the shank in the chuck.ĭrills come in standardized drill bit sizes. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation.

Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials.

JSTOR ( July 2021) ( Learn how and when to remove this template message)įrom top: Spade, brad point, masonry, and twist drills bits Drill bit (upper left), mounted on a pistol-grip electric drill A set of masonry drillsĭrill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section.

Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. The wire gauge number ranging from 107 to 1 and letters ranging from A to Z.This article needs additional citations for verification. Fractional sizes are measured in inches and metric sizes are measured in millimeters. In this drill bit size table, standard size drill bits available in several measurement systems, you can find wire gauge number, letter, fractional and metric drill sizes.

ANSI B94.11M-1979 specifies the size standard of straight shank twist drill bits with working length from 1/64 inch to 1 inch in increments of 1/64 inch.ĭrill Size Chart/Table – Drill Bit Dimensions Chart Fractional-inch drill bit sizes: the drill bit sizes are written as irreducible fractions.They are loosely based on the Stubs Steel Wire Gauge. Number and letter gauges do not follow a formula or standard increments. Number and letter gauge drill bit dimensions are often used for twist drill bits rather than other drill forms, and are still in common use in the U.S. Smaller sizes will be listed in the drill dimensions chart, but those are rarely encountered in practice. Number and letter gauge drill bit sizes: the number drill bit gauge sizes range from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest).

Drill bit sizes in 64ths chart