Standard Numbers for Design

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Pythagoras identified in music the scale relationships that work as an introduction to EP-calculation. Also technical design is based to "musical scale of engineering ", referred to as the standard basic sets of numbers. The standard basic sets of numbers are based on same idea than Archimedes' "Golden Rule  of Balance",  the lever arm length. The further away some value is from the smaller, the higher the value is compared to smaller.

The following are two definitions of the standard numbers, one of which is SFS standard and the second DIN standard. It is the same. It is elapsed time since about 2.500 years from Pythagoras times.

SFS 2964 standard 1973

"The standard numbers are to streamline and facilitate the magnitudes of free choice of the values. Standard numbers are applicable for any quantity at and are also used for other than standard parts. Additional numbers be exercised only when a specific reasons."

The above is a clear guideline to follow standard numbers. Have we passed the instruction and ignored it? Have  we perhaps unknowingly used the ratios? This occurs eg. when dimensioning steel profiles and the various components are based on the standard numbers.

The above is a clear guideline to follow standard numbers. Have we passed the instruction and ignored it? Have  we perhaps unknowingly used the ratios? This occurs eg. when dimensioning steel profiles and various components that are based on the standard numbers.

An example of HEA cross-section

1   -   1.25   -   1.6   -   2   -   2.5  -   3.15  -   4   -   5   -   6.3   -   8   -   10

HEA        100     120       160     200    240       300    400    500    600

The same when some other cross-section. Later we calculate the before showed.

Conveyor belt widths in mm.

1   -   1.25   -   1.6   -   2   -   2.5  -   3.15  -   4   -   5   -   6.3   -   8   -   10

                                                                         300     400    500    650     800   1000

                          1200     1600    2000

Metric screws (mm)

1   -   1.25   -  1.6   -   2   -   2.5  -   3.15  -   4   -   5   -   6.3   -   8   -   10

                                 M1,2     M1,6        M2      M2,5         M3         M4       M5        M6        M8       M10

                                 M12      M16        M20    (M24)         M32       M42

DIN 323, DIN 3

"Normal numbers are used in machinery and equipment to set selections, prescribing pressures, revolution, peripheral speed, powers, and similar variables as well as numerical values ​​of length to machine parts." As a general rule the dimensions must comply with the basic procedures without compromising the appropriateness of technical features or without wasting possible raw material.

Basic Series R 5

The standard numbers are rounded values ​​of geometric series of consecutive terms. Selected sets are the fifth root of ten (R 5 = 1.6), the tenth root of ten (R 10 = 1.25), the twentieth-root of ten (R 20 = 1.12), and the fortieth root of ten (R 40 = 1.06).

The numbers based on the standard series R 5, and R 10 have a large effect on product design. The standard series factor can be checked by multiplying five times 1.6:

1.6 x  1.6   x  1.6   x  1.6  x  1.6 = 10.(486)

 1 – 1.60 – 2.50 – 4.00 – 6.30 – 10

1.6⁵ = 10 

        1.25¹⁰ = 10 

                    1.12²⁰ = 10 

                               1.06⁴⁰ = 10

                                         (1.03⁸⁰ = 10)

Basic Series R 10

One or two set of standard numbers can not be explained the engineering design in practice, but it can model. The basic set of standard numbers R 5 is too few to product design.

Therefore, the standard numbers for the basic set of R 10 complete the set of R5, including the factor 1.25. Factor 1,25 is good for a number of products. Also to structural analysis, as well as machinery ageing, so it can say 1.25 is a major factor.

1.00 – 1.25 – 1.60 – 2.00 – 2.50 – 3.15 – 4.00 – 5.00 – 6.30 – 8.00 – 10.00

Basic series R 20 

1.00 – 1.12 – 1.25 – 1.40 – 1.60 – 1.80 – 2.00 – 2.24 – 2.50 – 2.80 – 3.15 – 3.55 – 4.00 – 450 – 5.00 – 5.60 – 6.30 – 7.10 – 8.00 – 9.00 10.00

The basic set R 20 of standard numbers is too dense to product design, product variations, because the number becomes large, but it is perfect for goods, such as pipes, etc.

Wheel diameters to crane end carriages

1   -   1,25   -   1,6   -   2   -   2,5  -   3,15  -   4   -   5   -   6,3   -   8   -   10

                       125       160     200     250      315     400   500 mm

Basic series R 40

The basic set of R 5 is preferred before R 10 series and the same when R10 to further R 20 series, etc. The series below is as the previous R 20 series, which we do not use for the EP-calculation. The product designer must be aware of the standard number series, because EP-calculation is largely based on the standard numbers.