ISO/DIS 484-1:2026(en)

ISO/TC 8/SC 3

Secretariat: ANSI

Date: 2026-01-22

Shipbuilding — Ship screw propellers—manufacturing tolerances —Part 1: Propellers of diameter greater than 2,50 m.

Construction navale - Hélices de navires - Tolérances de fabrication - Partie 1: Hélice de diamètre supérieur à 2,50 m

© ISO 2026

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Contents Page

Introduction..................................................................................................................v

1 Scope............................................................................................................................1

2 Normative references............................................................................................1

3 Field of application...................................................................................................1

4 Methods for measuring pitch..............................................................................1

4.1.1 Use of marking gauges........................................................................................2

4.1.2 Method with a graduated ring..........................................................................2

4.1.3 Method using coordinate measuring machine.............................................2

5 Methods for measuring the thickness of the section..................................2

6 Accuracy classes.....................................................................................................................................................................................................3

7 Tolerances on the pitch...................................................................................................................................................................................4

8 Tolerances on the extreme radius of the screw propeller.........................................................................................5

9 Tolerances on the thickness of the blade section................................................................................................................5

10 Checking and tolerances of the form of blade sections.................................................................................................5

11 Tolerances on the length of the blade sections......................................................................................................................9

12 Tolerances on the location of blades, reference lines, and blade contours..............................................9

12.1 Marking of lines of reference.................................................................................................................................................. 9

12.2 Tolerances on the contour of the leading edge......................................................................................................11

12.3 Tolerances on the angular deviation between two consecutive blades..........................................11

13 Tolerances on rake, axial position, and relative axial position of consecutive blades..............11

14 Surface finish..........................................................................................................................................................................................................12

15 Static balancing....................................................................................................................................................................................................13

16 Measuring equipment...................................................................................................................................................................................13

Bibliography.....................................................................................................................................................................................................................14

Introduction

The propeller manufacturer may choose any equipment and method that enables the tolerances to be verified to the required accuracy. The suitability of the chosen equipment and method needs to be demonstrated.

Measurement and evaluation as well as given tolerances in accordance with this standard are related to a defined net of discrete measuring points which shall embody the geometry of the propeller in a sufficient way.

The application of progressive measuring methods allows to step forward from a pointwise pattern to an area-measured pattern of propeller blades.

As long as no tolerances are defined for acceptable deviations between actual and nominal patterns, those shall be agreed between manufacturer and customer deduced from definitions of this standard in case those methods shall be used.

Shipbuilding — Ship screw propellers — Manufacturing tolerances — Part 1: Propellers of diameter greater than 2,50 m

This part of ISO 484 defines manufacturing tolerances of ship screw propellers of a diameter greater than 2,50 m.

NOTE Some deviations for the tolerance are permitted in certain cases subject to the discretion of the customer or of the designer and the customer.

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 1302, Geometrical Product Specifications (GPS) — Indication of surface texture in technical product documentation

This part of ISO 484 applies to monobloc, built-up, and controllable pitch propellers.

4.1 The principle of one method of measurement consists in setting out along a helicoidal line of radius, r, a certain length, PQ, corresponding to the desired angle, α, and in measuring the difference, h, in the heights of the points P and Q with respect to a reference plane (see Figure 1).

The length PQ shall be set out using one of the methods described in 4.1.1, 4.1.2, or 4.1.3.

NOTE Other methods giving the required accuracy may be used if necessary.

Key

1 small graduated ring

2 large graduated ring

Figure 1 — Pitch measurement

The length PQ shall be set out by means of marking gauges.

The length PQ shall be set out by means of angle, α, on a part of a graduated ring of suitable radius (see Figure 1).

The height coordinates are taken at defined measuring points by means of coordinate measuring machine, and they are related to each other (determination of height differences needed for pitch evaluation). Both Cartesian coordinate system (x, y, z) and polar coordinate system (α, r, h) can be applied alternatively in order to define measuring points P and Q.

5.1 The thickness of a cylindrical section at a point S shall be measured along direction SV (see Figure 2) on the plane tangent to the coaxial cylinder and perpendicular to the pitch line of the pressure side of the section (and only along direction SU perpendicular to the pressure side surface or direction S parallel to the propeller axis when defined in this way on the drawings).

Key

1 pressure side

2 suction side

3 cylindrical section

4 line of points U at the chordwise position of maximum thickness

5 developed section perpendicular to the pressure side along direction SU (left) and/or SUV (right)

6 developed cylindrical section along direction ST

7 pressure side

NOTE: left: measured position at propeller; right: cylindrical blade section rotated by 90°

Figure 2 — Thickness measurement

5.2 The maximum thickness at each radius shall be determined by means of a pair of outside callipers or from the profile obtained by plotting the thickness at various points: S, S1, S2, S3, etc.

The accuracy class shall be selected by the customer. The indications in Table 1 serve as guidance in this choice.

Table 1 — Accuracy of manufacturing

Table 2 — Pitch tolerances

7.1 Pitch shall be measured at least at the radii indicated in Table 3. By agreement between the interested parties, different radii may be measured.

Table 3 — Pitch measurement locations

7.2 The measurement of local pitches for Class S and Class I is further controlled as described in Clause 10.

7.3 The tolerances on the local pitch and on the mean pitch of each radius of each blade given in Table 2, a) and b) are increased by 50 % for sections at 0,4 R or less.

7.4 Should the propeller manufacturer wish to compensate for an error on the pitch (inside or outside the tabulated tolerances) by means of an alteration in the propeller diameter, he may do so only with the customer’s agreement.

7.5 The design pitch is the pitch of the reference line as defined below.

The design pitch line of a section is a helical reference for the section in question of which the section ordinates for the face and the back are given.

It could be a line joining the nose and tail of the section or any other conveniently placed helical line.

7.6 The local pitch at point B (Figure 1) is determined by measuring the difference in height between two points, P and Q, situated at equal distances from point B and on either side of the latter (BP = BQ) and by multiplying the difference in height by. This shall be compared with the local pitch as calculated from the design face offsets for the same points.

The distance between any two points used for a local pitch measurement may range between 100 mm and 400 mm. One pitch measurement is to be near the leading edge, one near the trailing edge, and there shall be at least two other pitch measurements in between. As far as possible, the pitch measurements should be consecutive.

7.7 The pitch per radius and per blade is determined for each radius by multiplying the difference in height between the most distant measuring points at each radius by .

7.8 The average pitch per blade is defined as the arithmetic mean (average) of the measured pitches per radius for the blade in question.

7.9 The average pitch for the screw propeller is defined as the arithmetic mean of the average pitches per blade.

8.1 The tolerances in Table 4 are expressed as percentages of screw propeller radius.

Table 4 — Radius tolerance

8.2 In the case of a ducted propeller, these tolerances may need to be reduced.

Table 5 — Blade thickness tolerance

Note For design thickness values >100 mm the percentage tolerances apply, for all others the absolute tolerances apply.

9.1 The thickness shall be measured at the same radii as those at which the pitch is measured.

9.2 The tolerances in Table 5 are expressed as percentages of the local thickness at chordwise position (S, S1, S2 etc.).

9.3 The maximum thicknesses according to the propeller design shall not be less, after deduction of the minus tolerance, than the thicknesses required by the Classification Society concerned.

10.1 These apply only to propellers of Class S and Class I and to the same radii as those at which the pitch is measured.

In case of CNC-machining of blade and edges, it can be agreed between the manufacturer and the customer to abstain from any further checking of the form of blade sections.

10.2 To avoid undue deviation in overall camber, the algebraic sum and difference of the percentage deviations resulting from any two consecutive measurements of local pitch shall be considered. Any algebraic sum and difference shall not exceed 1,5 times the allowable tolerance (for example, if the tolerance is ±2 %; the sum of consecutive deviations shall be within ±3 %, see Figure 3).

10.3 Alternatively, the satisfactory continuity of the cylindrical sections may be verified by the use of suitable flexible templates.

10.4 The leading and trailing edges shall be checked by templates, or equivalent devices, to demonstrate their accuracy to the drawing. These templates shall be calculated along a straight path or formed to the pitch and radius of the tested section. The length of these templates shall be about 20 % of the blade section length but not necessarily more than 120 mm.

10.4.1 Single part templates shall fit within the following tolerances of the face and the back:

— Class S: ±0,5 mm;

— Class I: ±0,75 mm.

10.4.2 Alternatively, by agreement between the manufacturer and the user, the edges shall be checked by templates made in three parts for each edge (see Figure 4) a short nose template controlling the final edge detail and two fairing templates from the nose, one to the face and one to the back, each covering about 20 % of the blade length but not necessarily more than 120 mm. These templates shall fit with the following tolerance:

— Class S: 0,25 mm;

— Class I: 0,35 mm.

In case of large skew of the blades (skew angle more than 25°), LE templates (having a corresponding shape) may be attached perpendicular to the leading edge contour alternatively by agreement between the manufacturer and the user. This holds for the area from 0,7 R to the tip. The templates shall be attached at the cross points of blade outline and nominal test radii, and they shall overlap at least 2 test radii, at which pitch, thickness, etc. will be checked, but not necessarily more than 300 mm length.

The number of templates to be applied is the same as for the conventional procedure.

Key

^a Theoretical outline of blade section (for reference).

^b Pitch difference is too high because the absolute value (IV-III = -3,5 %) is larger than allowed according to Table 2, a).

^c Pitch difference is too high because the absolute value (III + II = 3,5 %) is larger than allowed according to Table 2, a).

A deviation in local pitch X Heights measured

I – V intervals of measurements on pressure side

0, … 5 measured outline of blade section

NOTE The values which are too high are underlined because their absolute value is larger than the allowed value from 10.2 (local pitch tolerance from Table 2, a) multiplied with 1,5).

Figure 3 — Example for measurement and verification of blade section tolerances

Key

1 short nose template made to size + max tolerance

2 form templates for pressure and suction sides separated by 6 mm for independent application

3 theoretical suction side profile

4 contact surface for suction side

^a Leading edge (+6 mm).

^b Pressure side.

Figure 4 — Measurement using template

Table 6 — Blade length tolerances

11.1 The tolerances in Table 6 are expressed as percentages of the values of the ratio: diameter by the number of blades (D/Z).

11.2 The lengths of the sections of each blade shall be measured at five radii at least (Example: 0,3 R – 0,5 R – 0,7 R – 0,8 R – 0,95 R).

The reference line is positioned as a straight line on the drawing by location of the point M on the pressure side of the blade and point O on the axis of the propeller.

This point M shall be marked on a cylindrical section at a radius outside 0,5 R and, if possible, near 0,7 R.

In principle, it is selected in such a way that the line OM cuts the largest possible number of blade sections.

The ratio between the angles φE (leading edge) and φS (trailing edge) is indicated on the drawings (see Figure 5).

Point M’ on the manufactured propeller shall be determined in such a way that a ratio φE/φS as found on the drawings can be obtained at the considered radius (see Figure 6).

Figure 5 — Angles of blade leading and trailing edges of the propeller design

Figure 6 — Lines of reference of the manufactured propeller

The reference planes through points M’ are used to check the shape of the leading edge and skew angle, as well as the blade angular deviation.

NOTE For skew angle definition, see ISO 3715-1.

The tolerance shall be calculated on the radii according to Table 3 on the corresponding arcs and are valid for the arc lengths E’’M’’ (see Figure 6). They are given in percentages of D/Z in Table 6 (D = Diameter, Z = number of blades).

The tolerances for the distance E’’M’’ shall be double the values given in Table 6, provided that the contours of the blade edges are fair.

The tolerances shall be given by the following:

— Class S and I: ±1°;

— Class II and III: ±2°.

The rake is characterized by the position of the reference line PP’ [see Figure 7, a)]. This is measured by the distance to a plane, W, perpendicular to the axis of rotation of the screw propeller at three points (at least). A, B, and C situated at 0,3 R or 0,4 R, 0,6 R or 0,7 R, 0,9 R or 0,95 R.

Alternatively, the centre line of blade sections shall be used as reference line PP’ [see Figure 7, b)] for evaluation of rake in case of high-skewed propeller blades (skew angle >25°).

Table 7 gives the tolerances on these distances: d (A), d (B), and d (C) expressed as a percentage of the propeller diameter, D, to control the axial position of the blades. The same tolerances (and not double tolerances) are applicable to differences such as d (B) – d (C), for the same blade, to control the rake; and to differences such as d1 (C) – d2 (C), for two consecutive blades, to control the relative axial position.

Table 7 — Rake tolerances

Figure 7 — Blade rake and reference line

The surface texture of the blades, expressed as an arithmetic mean deviation, Ra in micrometres, in accordance with ISO 1302, shall have a roughness not greater than the following:

— 2 from the hub for propellers of Class S;

— 3 from the radius 0,3 R for propellers of Class I;

— 5 from the radius 0,4 R for propellers of Class II;

— 8 from the radius 0,5 R for propellers of Class III.

15.1 When finished, all propellers shall be statically balanced.

The maximum permissible balancing mass, p, (in kilograms) at the tip of the propeller blade is defined by:

or Km, whichever is smaller (1)

where

m is the mass of propeller in kilograms;

R is the radius of blade tip in metres;

n is the designed revolutions per minute of the propeller;

C and K are factors depending on class given in Table 8.

Table 8

15.2 In the case of a controllable pitch or built-up propeller, the manufacturer shall convince the user that the assembled propeller will be in accordance with the requirements of this Clause.

The maximum permissible inaccuracy of the measuring equipment shall not exceed half the tolerance on the dimension or quantity to be measured or, in the case of geometric measurements, 0,5 mm, whichever is greater.

Bibliography

[1] ISO 484‑2, Shipbuilding — Ship screw propellers — Manufacturing tolerances — Part 2: Propellers of diameter between 0,80 m and 2,50 m inclusive

[2] ISO 3715‑1, Ships and marine technology — Propulsion plants for ships — Part 1: Vocabulary for geometry of propellers