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Preferred metric sizes are a set of "international standards and "de facto standards that are designed to make using the metric system easier and simpler, especially in engineering and construction practices. One of the methods used to arrive at these preferred sizes is the use of "preferred numbers and "convenient numbers such as the "Renard series, the "1-2-5 series to limit the number of different sizes of components needed.

One of the largest benefits of such limits is an ensuing multiplicative or exponential reduction in the number of parts, tools and other items needed to support the installation and maintenance of the items built using these techniques. This occurs because eliminating one diameter fastener will typically allow the elimination of a large number of variations on that diameter (multiple thread pitches, multiple lengths, multiple tip types, multiple head types, multiple drive types, and the tools needed for installing each, including multiple drill bits (one for each different thread pitch, material, and fit combination).

## Food & Beverages

### Liquor Bottle Sizes

International agreements, including 75/106/EEC,[1] specify 0.1, 0.25 (​14), 0.375 (​38), 0.5 (​12), 0.75 (​34), 1, 1.5, 2, 3, and 5 litres as the capacities of liquor bottles allowed in international commerce.

## Building Construction

### System 32 Furniture

"System 32 is a standard for the design and manufacture of furniture, most commonly used in the design of cabinets, wherein the major parts (sides, doors, etc.) are available in increments of 32 mm, and shelf supports consist of columns of 5 mm holes on 32 mm centers.

### ISO 2848 Basic Module

The "ISO 2848 basic module is a unit of 100 mm, often represented by a single capital "M", along with 300 mm and 600 mm groupings, that is widely used for the widths of furniture in Europe.

• A standard metric (concrete) block is 190 mm wide, 390 mm long, and 190 mm high, which allows for 10 mm mortar joints in between bricks, giving a standard unit size of 200 mm square by 400 mm long.[2]
• A standard metric brick is 90 by 57 by 190 mm; with 10 mm of mortar, that produces a standard unit of 100 mm x 200 mm.[2]

## Office Equipment & Supplies

### ISO 216 Paper Sizes

"ISO 216 standard specifies the A sizes of paper, including the very common A4, wherein the base size of A0 is one square meter, and the ratio between the height and width is 2, which results in all sizes of paper having the same aspect ratio.

Also related is the set of pen thicknesses for technical drawings (0.13, 0.18, 0.25, 0.35, 0.50, 0.70, 1.00, 1.40, and 2.00 mm).

## Manufacturing

### ISO 261 and 262 Fastener Diameters

ISO 261 defines a set of preferred metric machine screw/bolt sizes, and "ISO 262 defines a subset of those; both are based roughly on "Renard series as defined in "ISO 3, "ISO 17, and "ISO 497. Given that even ISO 262 specifies a fairly large set of diameters, a much simplified set of preferred diameters was developed by one of the lead designers of ASME Z17.1 and ANSI B4.2, Knut O. Kverneland,[3] to reduce the list to 6 preferred sizes, and another 6 intermediate supplementary sizes.[4]

For each size bolt or screw and type of head, there is a corresponding size driver prescribed by various ISO standards, including:

• Internal hex drive: ISO 2936:2001 "Assembly tools for screws and nuts—Hexagon socket screw keys"
• External hex drive: ISO 4014, 4015, 4015, 4017, and 4018.
ISO 262 sizes 1st choice 2nd choice Internal hex, cap head Internal hex, button head Internal hex, flat head screws Internal hex, set screws R''5 R'10 Hex driver and wrench sizes M2.5 2.0 mm 2.0 mm M3 2.5 mm 2.0 mm 2.0 mm 2.0 mm M4 3.0 mm 2.5 mm 2.5 mm 2.5 mm 7 mm M5 4.0 mm 3.0 mm 3.0 mm 3.0 mm M6 5.0 mm 4.0 mm 4.0 mm 3.5 mm 10 mm M8 6.0 mm 5.0 mm 5.0 mm 5.0 mm M10 8.0 mm 6.0 mm 6.0 mm 6.0 mm 16 mm M12 10.0 mm 8.0 mm 8.0 mm 8.0 mm M16 14.0 mm 10.0 mm 10.0 mm 24 mm M20 17.0 mm 12.0 mm 12.0 mm M24 19.0 mm 36 mm M30

For each size bolt or screw and type of head, there is a corresponding size driver prescribed by Acument, the designer of the Torx drive system. As of 2018, there are no ISO standards for hexalobular drive sizes.

ISO 262 sizes 1st choice 2nd choice Pan head Flat head Socket head Socket Button Truss R''5 R'10 Torx driver and wrench sizes[5] M2.5 T8 T8 T8 M3 T10 T10 T10 T8 E4 M4 T20 T20 T25 T15 T15 E5 M5 T25 T25 T27 T25 T20 E6 M6 T30 T30 T30 T27 T30 E8 M8 T40 T40 T45 T40 T40 E10 M10 T50 T50 T50 T45 T50 E12 M12 T55 T55 T55 E14 M16 T70 T60 E20 M20 T90 E24 M24 T100 E32 M30 E36

For each size bolt or screw and type of head, there is a corresponding size driver prescribed by Acument, the designer of the Torx Plus drive system. As of 2018, there are no ISO standards for hexalobular drive sizes.

ISO 262 sizes 1st choice 2nd choice Pan head Flat head Socket head Socket Button Truss R''5 R'10 Torx Plus driver and wrench sizes[6] M2.5 8IP 8IP 8IP 4EP M3 10IP 10IP 10IP 8IP 5EP M4 20IP 15IP 20IP 15IP 15IP 7EP M5 25IP 20IP 27IP 25IP 20IP 8EP M6 30IP 27IP 30IP 27IP 30IP 10EP M8 45IP 30IP 45IP 40IP 40IP 14EP M10 50IP 50IP 50IP 45IP 50IP 16EP M12 55IP 55IP 55IP 55IP 55IP 20EP M16 70IP 60IP 26EP M20 90IP 32EP M24 100IP 40EP M30

If using just the 1st choice bolt sizes, the list of drivers and wrenches needed for all hex and Torx sizes are:[7]

Allen key Torx Torx Plus Hex wrench External Torx External Torx Plus
2 mm T8 8IP 5 mm E5 4EP
2.5 mm T15 15IP 7 mm E8 7EP
3 mm T20 20IP 10 mm E12 10EP
3.5 mm T25 27IP 16 mm E20 16EP
4 mm T27 30IP 24 mm E32 26EP
5 mm T30 45IP 36 mm 40EP
6 mm T45 50IP
8 mm T50 60IP
10 mm T60 70IP
14 mm T70 100IP
19 mm T100

### ISO 1307 Plastic Hose Sizes

ISO 1307:2006, Rubber and plastics hoses—Hose sizes, minimum and maximum inside diameters, and tolerances on cut-to-length hoses specifies nominal diameters for four different types of plastic hoses, including "Type C", which includes the typical "garden hose. Each nominal diameter specifies different ID minimum and maximum values. Notice that the nominal size is a Renard Series.

Nominal Size

ID

Type C

Non-mandrel-built

ID range

Inch

equivalent

ID

min max
3.2 n/a n/a
4 3.4 4.6
5 4.2 5.4
6.3 5.6 7.2 18 in
8 7.2 8.8 14 in
10 8.7 10.3 38 in
12.5 11.9 13.5 12 in
16 15.1 16.7 58 in
19 18.3 19.9 34 in
20 19.3 20.9
25 24.2 26.6 1 in
31.5 30.2 33.4 1 14 in
38 36.5 39.7 1 12 in

### ISO 6708 Nominal Diameter

Nominal diameter, abbreviated DN, is the designation system specified by ISO 6708 for specifying the diameter of trade sizes of metric pipework components, and is the metric equivalent to "Nominal Pipe Size.[8] It is among several ISO specifications that formalize "preferred numbers, and is referred to by numerous other international standards, including ISO 7598 and EN 10255. The complete set of DN values allowed by the standard are:

DN designation DN designation DN designation
DN 10 DN 250 DN 1 500
DN 15 DN 300 DN 1 600
DN 20 DN 350 DN 1 800
DN 25 DN 400 DN 2 000
DN 32 DN 450 DN 2 200
DN 40 DN 500 DN 2 400
DN 50 DN 600 DN 2 600
DN 60 DN 700 DN 2 800
DN 65 DN 800 DN 3000
DN 80 DN 900 DN 3200
DN 100 DN 1 000 DN 3 400
DN 125 DN 1 100 DN 3 600
DN 150 DN 1 200 DN 3 800
DN 200 DN 1 400 DN 4 000

The number following the DN is a "nominal value that is roughly the number of millimeters of a circular feature on the connection point of the pipe, fitting, coupling, etc., but often differing by a noticeable amount. If the DN value is related to the internal bore diameter of the feature, the size should be represented by DN/ID (for Inside Diameter), and if the DN value is related to the outside diameter, the size should be represented by DN/OD (for Outside Diameter).

The relationship between DN and "NPS pipe sizes are as follows. Note that the actual internal diameter varies depending on the pipe wall thickness.[9]

DN Actual OD NPS[10]
dimensionless mm dimensionless
DN 10 17.2 38
DN 15 21.3 12
DN 20 26.9 34
DN 25 33.7 1
DN 32 42.4 1 14
DN 40 48.3 1 12
DN 50 60.3 2
DN 65 76.1 2 12
DN 80 88.9 3
DN 100 114.3 4
DN 125 139.7 -
DN 150 168.3 6
DN 200 219.1 8
DN 250 273 10
DN 300 323.9 12
DN 350 355.6 14
DN 400 406.4 16
DN 450 457 18
DN 500 508 20
DN 600 610 24
DN 700 711 28
DN 750 762 32
DN 800 813 34
DN 900 914 36
DN 1 000 1016 40
DN 1 200 1220 48

## References

1. ^
2. ^ a b
3. ^ Kverneland, Knut O. (1996). Metric Standards for Worldwide Manufacturing. Amer Society of Mechanical Engineers. "ISBN "978-0791800416.
4. ^ Kverneland, Kurt. "TABLE 2 - FASTENER SIZES". Retrieved 2017-10-17.
5. ^ "Torx Drive System" (PDF).
6. ^ "Torx Plus Drive System" (PDF).
7. ^ "Torx Drive System" (PDF).
8. ^ "ISO 6708:1995: Pipework components -- Definition and selection of DN (nominal size)". Retrieved 2017-10-13.
9. ^ "Tube Sizes - ISO" (PDF). Retrieved 2017-10-13.
10. ^ "ISO 17292:2004, Metal ball valves for petroleum, petrochemical and allied industries". Retrieved 2017-10-16.
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