DIN 7715: tolerances, classes, successors

The five parts of DIN 7715

The August 1970 edition put the permissible dimensional deviations for all rubber parts on one sheet. With the ISO standard 3302 in mind, the German standard was split into separate parts from 1977. Since October 1999, moulded articles and extruded parts have been toleranced to DIN ISO 3302-1, hoses to DIN EN ISO 1307.

DIN 7715 AND SUCCESSORS · 1970 TO TODAY

1970 · AUGOne sheet for all rubber parts
1977 · FEBSplit into parts
1979 · NOVPart 5 for sheets, still valid
1983 · NOVPart 3 revised
1999 · OCTDIN ISO 3302-1 replaces parts 2 and 3
2008 · APRDIN EN ISO 1307 for hoses
2018 · JUNEDIN ISO 3302-1, current edition

▮ VALID TODAY▮ WITHDRAWN OR REPLACED

PartSubjectEditionStatus at DIN MediaSuccessor

DIN 7715-1Hard rubber articles1977-02withdrawnnone named

DIN 7715-2Moulded articles in soft rubber (elastomers)1977-02withdrawnDIN ISO 3302-1

DIN 7715-3Extruded articles in soft rubber (elastomers)1983-11withdrawnDIN ISO 3302-1

DIN 7715-4Hoses1977-02withdrawnDIN EN ISO 1307

DIN 7715-5Sheets and sheet articles in soft rubber (elastomers)1979-11current, with warning noticestill valid

Part 3 uses the German term ‘Spritzartikel’ for extruded parts; its English title is ‘extruded rubber products’. Part 3 first appeared in February 1977 and in a revised version in November 1983. The warning notice on part 5 goes back to a correction in DIN-Anzeiger 11/1980: in the last line of table 1 the ± sign is missing before the per centages.

DIN 7715-5: classes P1 to P3 for sheets and punched parts

Part 5 applies to vulcanised soft rubber sheets with and without inserts, with a smooth or profiled surface, and to articles made from them. It does not apply to sheets and articles made of cellular elastomers. The standard distinguishes three tolerance classes:

ClassApplication

P1, fine gradeHigh-precision sheets, such as sheets made in press moulds.

P2, medium gradeStandard commercial quality, such as sheets with a smooth or fabric-textured surface and articles punched from vulcanised sheets or cut to a template.

P3, coarse gradeSheets and articles without special dimensional requirements, such as with a profiled or coarse fabric-textured surface, and parts cut without a template.

As a rule, the standard says the medium grade should be chosen. The fine grade only makes sense where higher accuracy is unavoidable, and always means more effort. The permissible deviations per class and nominal size range are in table 1 of DIN 7715-5.

DIN ISO 3302-1: successor for moulded and extruded parts

DIN ISO 3302-1 governs dimensional tolerances for finished rubber products. The first German edition of October 1999 replaced DIN 7715-2 and DIN 7715-3. The current edition is June 2018, which adopts ISO 3302-1:2014. It sets classes for limit deviations and their values for moulded, extruded and calendered parts in solid rubber, plus the test methods for verification. Not covered are precision O-rings, calendered composite products such as rubber-coated fabric, and products with an applied rubber coating.

Moulded parts: classes M1 to M4

For solid rubber moulded parts the standard provides four tolerance classes:

TOLERANCE CLASSES MOULDED PARTS · DIN ISO 3302-1FROM FINE TO COARSE

M1Precision moulded parts, precision moulds, tight compound control

M2High-quality moulded parts

M3Good-quality moulded parts

M4No critical dimensional requirements

▮ NOMINAL SIZE▮ TOLERANCE ZONE, SCHEMATIC

Fixed dimensions and closure dimensions

Moulding uses more rubber than the cavity holds. The excess escapes as flash and can stop the mould parts from closing fully. The standard therefore gives two series of tolerances. Fixed dimensions (F) are affected neither by flash thickness nor by lateral offset of the mould parts. Closure dimensions (C) can change due to both. The standard has its own classification for the flash itself.

Extrusions and calendered sheeting

Extruded parts need larger tolerances than moulded parts, because the rubber swells after leaving the die and shrinks and distorts during vulcanisation. They have their own classes:

Classes for extrusions
E1 to E3 for cross-section dimensions of unsupported extrusions
EN1 to EN3 for cross-section dimensions of extrusions made on a mandrel
EG1 and EG2 for outside dimensions and EW1 and EW2 for wall thicknesses of ground extrusions
L1 to L3 for cut lengths and EC1 to EC3 for the thickness of cut sections

Calendered sheeting is toleranced to ST1 to ST3 in thickness and SW1 to SW3 in width.

Stating the tolerance class on the drawing

Under DIN ISO 3302-1, different dimensions on the same drawing may follow different classes. If the drawing names no class, the largest tolerance of the relevant table applies. The purchaser and manufacturer agree which class to apply. Tighter classes should only be required where the application needs them, and only for critical dimensions, because effort and cost rise with accuracy. Softer vulcanisates below 50 IRHD usually need larger tolerances than harder ones.

A tolerance zone may also be stated asymmetrically as long as its total width stays the same. Instead of ±0.4, +0.8/0 is then possible, for example.

For sheets to DIN 7715-5 the standard describes the entry precisely. The title block states DIN 7715 with the tolerance class appended under “dimensions without tolerance to:“ or “general tolerances to:“, in the standard’s example P3. Dimensions that follow a different class are entered directly at the dimension. If there is no reference at all, the notes to the standard say class P3 can be assumed as trade practice. A reference to DIN 7715 without a class, or “coarse DIN 7715“, refers to the outdated 1970 edition, whose values may no longer be used for new production and order documents.

When measurements are taken

Under DIN ISO 3302-1, solid rubber parts are measured no earlier than 16 hours after vulcanisation, in case of dispute no earlier than 72 hours. Measurement must be completed within three months of dispatch or before installation, whichever comes first. Parts are measured at standard temperature after conditioning to ISO 23529, without deforming them.

Tolerances at JRT

Parts from JRT follow the DIN standards and tolerances of their product group, because different materials and production methods require their own tolerances.

AUSBAUTo which tolerance standard and class do you make moulded parts if the drawing names no class?

AUSBAUWhich tolerance standard and class do you state for hoses today, and does “DIN 7715-4 S2 and SL2“ from the old standards overview still apply?

FAQ: DIN 7715 and tolerances for rubber parts

Is DIN 7715 still valid?

Only part 5 for sheets and sheet articles in soft rubber. DIN Media lists DIN 7715-5:1979-11 as current, parts 1 to 4 are withdrawn.

Which standard replaces DIN 7715 part 2?

DIN ISO 3302-1. Its 1999-10 edition replaced parts 2 and 3, and the 2018-06 edition is current.

Which standards apply to moulded parts?

Dimensional tolerances of solid rubber moulded parts follow DIN ISO 3302-1 with classes M1 to M4. Which other standards and regulations apply depends on the product group and requirement.

What does M3 mean for moulded rubber parts?

M3 is a tolerance class from DIN ISO 3302-1 and stands for good-quality moulded parts. M1 and M2 are finer, M4 is coarser.

Which tolerance applies if the drawing states no class?

Under DIN ISO 3302-1, the largest tolerance of the relevant table. For sheets to DIN 7715-5, the notes to the standard name class P3 as trade practice.

Which standard applies to hose tolerances?

DIN 7715-4 has been withdrawn and replaced by DIN EN ISO 1307. The current edition is 2008-04, with hose sizes, minimum and maximum inside diameters and tolerances for hoses cut to length. Individual agreements are possible, especially for handmade articles.