Drill bits are the cutting tools of drilling machines. They can be made in any size to order, but standards organisations have defined sets of sizes that are produced routinely by drill bit manufacturers and stocked by distributors. Drill bits are the working end of drill tools. ... // Hand held A bit and brace, a hand-powered drill. ...

In the US, 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 Standard on replacing gauge size drill bits with metric sizes in the UK was first published in 1959. Wikiquote has a collection of quotations by or about: United States Wikinews has news related to this article: United States United States government CIA World Factbook Entry for United States House. ... British Standards is the new name of the British Standards Institute and is part of BSI Group which also includes a testing organisation. ... 1959 was a common year starting on Thursday of the Gregorian calendar. ...

Metric Drill Bit Sizes

Metric drill set, 1.0 - 6.0 mm by 0.1 mm, jobber length

Metric drill bit sizes define the diameter of the bit in terms of standard metric lengths. Standards organisations 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. Image File history File links Download high resolution version (757x1297, 108 KB)Set of metric high speed steel twist drills. ... Image File history File links Download high resolution version (757x1297, 108 KB)Set of metric high speed steel twist drills. ... See: International System of Units, colloquially called the Metric System, and also metrication. ...

From 0.2 through 0.98 mm, sizes are defined as

• N * 0.1 mm,
• N * 0.1 + 0.02 mm,
• N * 0.1 + 0.05 mm, and
• N * 0.1 + 0.08 mm, with N an integer from 2 through 9.

From 1.0 through 2.95 mm, sizes are defined as

• N * 0.1 mm and
• N * 0.1 + 0.05 mm, with N an integer from 10 through 29.

From 3.0 through 13.9 mm, sizes are defined as

• N * 0.1 mm, with N an integer from 30 through 139.

From 14.0 through 25.0 mm, sizes are defined as

• M * 1 mm,
• M * 1 + 0.25 mm,
• M * 1 + 0.5 mm, and
• M * 1 + 0.75 mm, with M an integer from 14 through 25.

In smaller sizes, bits are available in smaller diameter increments. This reflects both the smaller drilled hole diameter tolerance possible on smaller holes, and also the wishes of designers to have drill bit sizes available within at most 10% of an arbitrary size hole.

The price and availability of particular size bits does not change uniformly across the size range. Bits at size increments of 1 mm are most commonly available, and lowest price. Sets of bits in 1 mm increments might be found on a market stall. In 0.5 mm increments, any hardware store. In 0.1 mm increments, any engineers' store. Sets are not commonly available in smaller size increments, except for drill bits below 1 mm diameter. Drill bits of the less routinely used sizes, such as 2.55 mm, would have to be ordered from a specialist drill bit supplier. This subsetting of standard sizes is in contrast to general practice with number gauge drill bits, where it is rare to find a set on the market which does not contain every gauge.

Metric dimensioning is routinely used for drill bits of all types, although the details of BS328 apply only to twist drill bits. For example, a set of forstner bits may contain 10, 15, 20, 25 and 30 mm diameter cutters.
Drill bits are the working end of drill tools. ...

Fractional Inch Drill Bit Sizes

Fractional inch drill bit sizes are still in common use in the US. In the past, they were popular elsewhere, but now have been largely discarded in favour of metric sizes.

ANSI B94.11M-1979 sets size standards for jobber length straight shank twist drill bits from 1/64 inch through 1 inch in 1/64 inch increments. For morse taper shank drill bits, the standard continues in 1/64 inch increments up to 1 3/4 inch, then 1/32 inch increments up to 2 1/4 inch, 1/16 inch increments up to 3 inches, 1/8 inch increments up to 3 1/4 inches, and a single 1/4 inch increment to 3 1/2 inches.

One disadvantage of this scheme of sizing is that the size increment between drill bits is very large for the smaller sizes, 100% for the first step. The implication is that number gauge drill bits have to be used to bridge the gaps.

Another disadvantage is the convention in labelling the bits. Rather than an integral number of 64ths of an inch, drill bit sizes are written down as irreducible fractions. So, instead of 78/64 inch, or 1 14/64 inch, the size is always written as 1 7/32 inch. This can lead to confusion and mistakes unless great care is taken. An irreducible fraction is a fraction a/b, where the numerator a is an integer and the denominator b is a positive integer, such that there is not another fraction c/d with c smaller in absolute value than a and 0<d<b, and c and d are integers...

US Number and Letter Gauge Drill Bit Sizes

A #80 drill bit.

Number and letter gauge drill bit sizes are still in common use in the US. In the past, they were popular elsewhere, but now have been largely discarded in favour of metric sizes. A complication of using a gauge rather than a standard measurement of length is that the user always has to refer to a table of gauge sizes. For example, to drill a hole which is 10 thou bigger than a 1/8 inch bolt, the user must first work out that 1/8 inch is 125 thou, so the hole size needed is 135 thou, and then must look up in a reference book which gauge drill bit has this diameter - a number 29. Image File history File links Download high resolution version (1024x768, 123 KB)A #80 drill bit (.0135 inch diameter) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1024x768, 123 KB)A #80 drill bit (.0135 inch diameter) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Wikiquote has a collection of quotations by or about: United States Wikinews has news related to this article: United States United States government CIA World Factbook Entry for United States House. ... Most modern English speakers think of thou as a relic of Shakespeares day Thou is the old second person singular pronoun of the English language. ...

Number drill bit gauge sizes are analogous to, but different from, american wire gauge. Here's a conversion table. American wire gauge (AWG) is used in the United States and other countries as a standard method of denoting wire diameter, especially for non-ferrous, electrically conducting wire. ...

Number gauge is routinely used from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest). Number gauge is actually defined at least down to size 97, but these smaller sizes are rarely encountered. It happens that as the technology for making small drill bits and drilling small holes has become more available, metric measurements have become the norm.

Number and letter gauge drill bits are almost always twist drill bits. There is no particular reason why the gauge cannot be used to measure bits of other types, but the gauge covers a size range across which the twist drill bit is the most commonly used. Drill bits are the working end of drill tools. ...

The gauge-to-diameter conversion does not follow a set formula, but rather was defined as a useful and practical measure. The graph shows how gauge diameters change with gauge. Each step along the horizontal axis is one gauge size. The step size between adjacent gauges is smaller for smaller gauges. This is appropriate, because the tolerance of the diameter of drilled holes is closer for smaller drill bits. The increment from one gauge to the next for a number 92 drill bit at 0.2 mm diameter is just 5%, compared to 10% for standard metric sizes. Image File history File links Graph of US number and letter gauge drill sizes. ...

Jobber Length Drill

Jobber Length Drills are standard drills, as compared with screw machine drills which have a much shorter length of flute. As a result screw machines are much more rigid, but cannot drill holes as deep as jobber length drills.

Long Series Drill Bits

Centre Drill Bit Sizes