The wire gauge number ranging from 107 to 1 and letters ranging from A to Z. 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 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).RF Cafe also has drill size tables for lettered drill size varieties. This particular page presents the numbered drill size series. Decimal drill sizes further include both SAE units and metric units. In the second column the letter drill sizes in inches are given. Drill bits are available in hundreds of sizes, and the size designations include letters, numbers, decimals, and fractions. The chart below will show you the drill bit sizes of all the lettered drill bits from A to Z. A 1/4-20 thread uses an 'F' size drill,but you aren't going to die if you use a close fractional drill substitute. I use them seldom,so can't recall the exact beginning and ending sizes. Besides, when you want to obtain maximum thread depth, lettered drill bits are used. The letter drills are drills in larger sizes from ABOUT 1/4' to ABOUT 1/2' range. The drill size chart contains tools up to 1.5 inches in diameter, but larger tools are also commonly used. Moreover, number and letter sizes are also used for twist drill bits, more than other forms, as their ranges encompass the sizes used more in twist drills. The wire gauge and letter systems refer to tool diameters that increase as the wire gauge decreases from 107 to 1 and then continues from A to Z. Since they fall in the sizes between those two types, they are used whenever a precision-sized hole is needed to be made. The most common uses for lettered and numbered drill bits are for using taps since you won’t probably find the exact match for fractional or metric sizes, but you can get close to them by using lettered or numbered bits. Drill bits are available in hundreds of sizes, and the size designations include letters, numbers, decimals, and fractions. 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. That is why numbered and lettered drill bits were developed to make up the gaps between these two sizes. What are letter drill bits used for?Īs we’ve seen, most of the measurement systems followed for drill bits are metric and fractional measurements. In other words, lettered bits are simply the larger versions of the numbered wire sizes. These lettered drill bits fall in between the normal 1/64 or 1mm jumps between the sizes of the other two sets. Here A is the smallest and Z is the largest. They are denoted by the letters from A to Z. The numbered ones have gauge sizes ranging from 80 to 1 the number 80 is the smallest while 1 is the biggest. Other than the drill bit sizes mentioned earlier we also have numbered and lettered drill bit sizes. Style A charts provide decimal equivalents of fractions, wire gauge drill sizes, letter drill sizes, and metric sizes. Fractional drill bit sizes, on the other hand, make inch-sized products. Well, the metric drill sizes are defined by the diameter of the bit in terms of metric lengths. What is the difference between these sizes? In nearly all other countries, the metric system sizes are maintained. the measurement system for drill bits is the fractional-inch and gauge bit sizes.
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