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Preferred metric sizes

Preferred metric sizes is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Preferred metric sizes rather than just read about it. In short: 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 and 1-2-5 series, to limit the number of different sizes of components…

Preferred metric sizes — main illustration
Preferred metric sizes — illustration

Key takeaways

  • Preferred metric sizes belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Preferred metric sizes to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Preferred metric sizes from memory before moving on to harder problems.

Reference excerpt

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 and 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 and beverages

Liquor bottle sizes

International agreements, including 75/106/EEC, specify the capacities of liquor bottles allowed in international commerce as the following 10 sizes:

100 ml (1⁄10 L) 250 ml (1⁄4 L) 375 ml (3⁄8 L) 500 ml (1⁄2 L) 750 ml (3⁄4 L) 1 L 1.5 L 2 L 3 L 5 L In the United States, the alcohol industry switched to metric bottle sizes on October 1, 1976, abandoning the existing 38 sizes of bottles and instead adopting the following 6 sizes:

50 mL (miniature) 200 mL (replaced the half-pint) (≈237 mL is a U.S. half-pint) 500 mL (replaced the pint) (≈473 mL is a U.S. pint) 750 mL (replaced the fifth) (≈757 mL is a fifth of a U.S. gallon) 1000 mL (replaced the quart) (≈946 mL is a U.S. quart) 1750 mL (replaced the half-gallon) (≈1893 mL is a half U.S. gallon)

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. 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.

Office equipment and 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 {\displaystyle {\sqrt {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, to reduce the list to 6 preferred sizes, and another 6 intermediate supplementary sizes.

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 2936:2014 "Assembly tools for screws and nuts—Hexagon socket screw keys" External hex drive: ISO 4014, 4016, 4017, and 4018

For Torx bolts, 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.

Similarly, for Torx Plus bolts, 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 1307 plastic hose sizes

See also:

ISO 6708 Nominal Diameter (for garden 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. The nominal size is a Renard series.

ISO 6708 nominal pipe diameter

Nominal diameter, abbreviated DN (diamètre nominal/Durchmesser nach Norm), 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. 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:

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.

See also Adjustable shelving, used in logistics with items and carriers of various standardised and non-standardised sizes Eurocontainer, a system for boxes that can be used for reusable packaging for transport and storage Gastronorm, a standard for professional kitchenware tray and container sizes ISO metric screw thread, the international standard for machine screw threads OpenStructures, open specification for modular interfaces in hardware based on a geometrical grid

References

Illustrations

Preferred metric sizes: Use of preferred metric sizes is common in engineering designs
Use of preferred metric sizes is common in engineering designs
Preferred metric sizes: Champagne bottles in various sizes, probably 200 ml, 375 ml, 750 ml, 1.5 L, 3 L, 6 L, 9 L, 12 L and 18 L.
Champagne bottles in various sizes, probably 200 ml, 375 ml, 750 ml, 1.5 L, 3 L, 6 L, 9 L, 12 L and 18 L.
Preferred metric sizes: Shelf where the shelf bearing holes are placed with 32 mm distances from center to center, giving flexible choices for shelve positioning.
Shelf where the shelf bearing holes are placed with 32 mm distances from center to center, giving flexible choices for shelve positioning.
Preferred metric sizes: Cross section of a wooden joist layer, where 6 M (or 6 modules) indicates a distance of 600 mm.
Cross section of a wooden joist layer, where 6 M (or 6 modules) indicates a distance of 600 mm.
Preferred metric sizes: A-series paper sizes.
A-series paper sizes.

Worked examples

Example 1 — a first encounter with Preferred metric sizes

Start with the simplest possible case. Write down what Preferred metric sizes claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Preferred metric sizes before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Preferred metric sizes ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Preferred metric sizes

In research
Preferred metric sizes appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Preferred metric sizes in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Preferred metric sizes is common in secondary-school and first-year university syllabi. It links to neighbouring topics International standards, Metric system, so understanding it makes those chapters shorter.
In everyday life
Look for Preferred metric sizes outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Preferred metric sizes in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Preferred metric sizes means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Preferred metric sizes out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Preferred metric sizes in simple terms?

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 a…

Why does Preferred metric sizes matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Preferred metric sizes?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Preferred metric sizes.

Tags

  • International standards
  • Metric system

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