DIN 76-1

June 2004

D EUTSCHE NORM

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Thread run-outs and thread undercuts for ISO metric threads as in DIN 13-1

76-1 Supersedes December 1983 edition.

ICS 21.040.10 Gewindeausläufe und Gewindefreistiche – Teil 1: Für Metrisches ISO-Gewinde nach DIN 13-1

In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker.

Foreword This standard has been prepared by Technical Committee Fachgrundnormen of the Normenausschuss Mechanische Verbindungselemente (Fasteners Standards Committee). It is based on International Standards ISO 3508 : 1976 and ISO 4755 : 1983. As a departure from ISO 4755, which specifies only one type of thread undercut with g2 max = 3 P, this standard specifies two types, i.e. type A with g2 max = 3,5 P (normal design) and type B with g2 max = 2,5 P (short design). Type B thread undercuts are intended for use on a case-by-case basis, where required for technical reasons; the use of special tools is necessary here. It should be noted that ISO 3508 and ISO 4755 do not contain specifications for thread run-outs and thread undercuts for internal threads. Amendments This standard differs from the December 1983 edition in that it has been editorially revised. Previous editions DIN 2352: 1924-11; DIN LON 369-1 = DIN 30140-1:1936-12; DIN 76-1: 1924-09, 1943-04, 1953-11, 1965-09, 1967-06, 1975-09, 1983-12.

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All dimensions are in millimetres.

1

Scope

This standard specifies dimensions for thread run-outs and thread undercuts for bolts, screws and similar components with external or internal ISO metric (coarse or fine pitch) thread as in DIN 13-1 and DIN ISO 261.

2

Normative references

This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies. DIN 13-1 DIN 76-2 DIN 76-3 DIN EN 28839

General purpose ISO metric screw threads – Nominal sizes for 1 mm to 68 mm diameter coarse pitch threads Thread run-outs and thread undercuts for pipe threads conforming to ISO 228-1 Thread run-outs and thread undercuts for trapezoidal threads, buttress threads, knuckle threads and other coarse pitch threads Mechanical properties of fasteners – Bolts, screws, studs and nuts made of non-ferrous metals (ISO 8839 : 1986) Document comprises 5 pages. Translation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text.

© No part of this translation may be reproduced without the prior permission of DIN Deutsches Institut für Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, has the exclusive right of sale for German Standards (DIN-Normen).

English price group 7 www.din.de www.beuth.de

10.04

9587848

Page 2 DIN 76-1 : 2004-06 DIN EN ISO 898-1 DIN ISO 261 ISO 3508 : 1976 ISO 4755 : 1983

3

Mechanical properties of fasteners made of carbon steel and alloy steel – Part 1: Bolts, screws and studs (ISO 898-1 : 1999) ISO general purpose metric screw threads – General plan (ISO 261 : 1998) Thread run-outs for fasteners with thread in accordance with ISO 261 and ISO 262 Fasteners – Thread undercuts for external metric ISO threads

Dimensions and designation

3.1

External threads

3.1.1 Thread run-outs Thread run-out dimensions shall be as given in figures 1 and 2 and table 1.

Key to figure 1 Shank diameter R pitch diameter Figure 1: Thread run-out dimensions (notation)

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3.1.2

Distance from last full form thread to bearing face, a (for fully threaded components)

Figure 2: Dimension a (notation) 3.1.3 Thread undercuts Thread undercut dimensions shall be as given in figure 3 and table 1. It should be noted that fasteners with thread undercut do not meet the requirements for minimum breaking load as specified in DIN EN ISO 898-1 or minimum breaking torque as specified in DIN EN 28839. Type A, with g1 and g2 of normal design Type B, with g1 and g2 of short design

Figure 3: Thread undercut dimensions (notation)

Page 3 DIN 76-1 : 2004-06 Designation of a type B thread undercut (B):

Thread undercut DIN 76 – B Table 1: Dimensions of thread run-outs and thread undercuts for external threads Thread run-out

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Thread pitch P

Nominal diameter(s), d (coarse thread)

x1

x2

Distance a1

Max.

a2

Thread undercut a3

dg

Max.

g1

g2

r

Min.

Max.

|

Type A Type B Type A Type B Normal 1)

Short 2)

Normal 3)

Short 4)

Long 5)

h13 6)

(normal) 7) (short) 8) (normal) 7) (short) 8)

0,2 0,25 0,3

– 1; 1,2 1,4

0,5 0,6 0,75

0,25 0,3 0,4

0,6 0,75 0,9

0,4 0,5 0,6

– – –

d – 0,3 d – 0,4 d – 0,5

0,45 0,55 0,6

0,25 0,25 0,3

0,7 0,9 1,05

0,5 0,6 0,75

0,1 0,12 0,16

0,35 0,4 0,45

1,6; 1,7; 1,8 2; 2,3 2,2; 2,5; 2,6

0,9 1 1,1

0,45 0,5 0,6

1,05 1,2 1,35

0,7 0,8 0,9

– – –

d – 0,6 d – 0,7 d – 0,7

0,7 0,8 1

0,4 0,5 0,5

1,2 1,4 1,6

0,9 1 1,1

0,16 0,2 0,2

0,5 0,6 0,7

3 3,5 4

1,25 1,5 1,75

0,7 0,75 0,9

1,5 1,8 2,1

1 1,2 1,4

– – –

d – 0,8 d–1 d – 1,1

1,1 1,2 1,5

0,5 0,6 0,8

1,75 2,1 2,45

1,25 1,5 1,75

0,2 0,4 0,4

0,75 0,8 1

4,5 5 6; 7

1,9 2 2,5

1 1 1,25

2,25 2,4 3

1,5 1,6 2

– 3,2 4

d – 1,2 d – 1,3 d – 1,6

1,6 1,7 2,1

0,9 0,9 1,1

2,6 2,8 3,5

1,9 2 2,5

0,4 0,4 0,6

1,25 1,5 1,75

8 10 12

3,2 3,8 4,3

1,6 1,9 2,2

3,75 4,5 5,25

2,5 3 3,5

5 6 7

d–2 d – 2,3 d – 2,6

2,7 3,2 3,9

1,5 1,8 2,1

4,4 5,2 6,1

3,2 3,8 4,3

0,6 0,8 1

2 2,5 3

14; 16 18; 20; 22 24; 27

5 6,3 7,5

2,5 3,2 3,8

6 7,5 9

4 5 6

8 10 12

d–3 d – 3,6 d – 4,4

4,5 5,6 6,7

2,5 3,2 3,7

7 8,7 10,5

5 6,3 7,5

1 1,2 1,6

3,5 4 4,5

30; 33 36; 39 42; 45

9 10 11

4,5 5 5,5

10,5 12 13,5

7 8 9

14 16 18

d–5 d – 5,7 d – 6,4

7,7 9 10,5

4,7 5 5,5

12 14 16

9 10 11

1,6 2 2

5 5,5 6

48; 52 56; 60 64; 68

12,5 14 15

6,3 7 7,5

15 16,5 18

10 11 12

20 22 24

d–7 d – 7,7 d – 8,3

11,5 12,5 14

6,5 7,5 8

17,5 19 21

12,5 14 15

2,5 3,2 3,2

The dimensions specified are approximately equal to

2,5 P

1,25 P

3P

2P

4P

–

–

–

3,5 P

2,5 P

0,5 P

1)

x1 to be used where no other indications are made in product standards or on drawings.

2)

x2 to be used where a short thread run-out is required for technical reasons.

3)

a1 to be used where no other indications are made in product standards or on drawings.

4)

a2 to be used for slotted and cross recessed head screws and in cases where a short distance is required for technical reasons.

5)

a3 to be used for screws assigned to product grade C.

6)

Tolerance h12 for screw threads up to 3 mm nominal diameter.

7)

Type A to be used where no other indications are made in product standards or on drawings.

8)

Type B to be used where a short thread undercut is required for technical reasons.

Page 4 DIN 76-1 : 2004-06

3.2

Internal threads (blind tapped holes)

2)

3)

3.2.1 Blind tapped holes with thread run-out The dimensions of blind tapped holes with thread run-out shall be as given in figure 4 and table 2.

1)

Key to figure b Useful thread length Limit deviations for the calculated value of t: +00,5 P. da, min = 1 d, da, max = 1,05 d. For nuts, the countersink diameters, da, are specified in the relevant dimensional standards. 3 ) Special designs (e.g. 90° or 60° countersink) shall be indicated on the drawing. A 60° countersink is recommended for studs with thread run-out and for centre holes, and a parallel countersink is recommended for light alloy studs. 1) 2)

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Figure 4: Dimensions of blind tapped holes with thread run-out (notation)

3.2.2 Blind tapped holes with thread undercut The dimensions of blind tapped holes with thread undercut shall be as given in figure 5 and table 2. Type C, with g1 and g2 of normal design Type D, with g1 and g2 of short design

1)

Key to figure b Useful thead length 1)

Limit deviation for the calculated value of t:

+0,5 0

P.

Other dimensions as in figure 4. Figure 5: Dimensions of blind tapped holes with thread undercut (notation) Designation of a type C blind tapped hole with thread undercut:

Blind tapped hole DIN 76 – C

Page 5 DIN 76-1 : 2004-06 Table 2: Dimensions of thread run-outs and thread undercuts for internal threads

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Thread pitch, P

Nominal diameter(s), d (coarse thread)

Thread run-out *) (guideline values)

Thread undercut

e1

e2

e3

dg

Normal 1)

Short 2)

Long 3)

H13

g1 Min. Type C Type D

g1 Max. Type C Type D

r |

(normal) 4) (short) 5) (normal) 4) (short) 5)

0,2 0,25 0,3

– 1; 1,2 1,4

1,3 1,5 1,8

0,8 1 1,2

2 2,4 2,9

d + 0,1 d + 0,1 d + 0,1

0,8 1 1,2

0,5 0,6 0,75

1,2 1,4 1,6

0,9 1 1,25

0,1 0,12 0,16

0,35 0,4 0,45

1,6; 1,7; 1,8 2; 2,3 2,2; 2,5; 2,6

2,1 2,3 2,6

1,3 1,5 1,6

3,3 3,7 4,1

d + 0,2 d + 0,2 d + 0,2

1,4 1,6 1,8

0,9 1 1,1

1,9 2,2 2,4

1,4 1,6 1,7

0,16 0,2 0,2

0,5 0,6 0,7

3 3,5 4

2,8 3,4 3,8

1,8 2,1 2,4

4,5 5,4 6,1

d + 0,3 d + 0,3 d + 0,3

2 2,4 2,8

1,25 1,5 1,75

2,7 3,3 3,8

2 2,4 2,75

0,2 0,4 0,4

0,75 0,8 1

4,5 5 6; 7

4 4,2 5,1

2,5 2,7 3,2

6,4 6,8 8,2

d + 0,3 d + 0,3 d + 0,5

3 3,2 4

1,9 2 2,5

4 4,2 5,2

2,9 3 3,7

0,4 0,4 0,6

1,25 1,5 1,75

8 10 12

6,2 7,3 8,3

3,9 4,6 5,2

10 11,6 13,3

d + 0,5 d + 0,5 d + 0,5

5 6 7

3,2 3,8 4,3

6,7 7,8 9,1

4,9 5,6 6,4

0,6 0,8 1

2 2,5 3

14; 16 18; 20; 22 24; 27

9,3 11,2 13,1

5,8 7 8,2

14,8 17,9 21

d + 0,5 d + 0,5 d + 0,5

8 10 12

5 6,3 7,5

10,3 13 15,2

7,3 9,3 10,7

1 1,2 1,6

3,5 4 4,5

30; 33 36; 39 42; 45

15,2 16,8 18,4

9,5 10,5 11,5

24,3 26,9 29,4

d + 0,5 d + 0,5 d + 0,5

14 16 18

9 10 11

17,7 20 23

12,7 14 16

1,6 2 2

5 5,5 6

48; 52 56; 60 64; 68

20,8 22,4 24

13 14 15

33,3 35,8 38,4

d + 0,5 d + 0,5 d + 0,5

20 22 24

12,5 14 15

26 28 30

18,5 20 21

2,5 3,2 3,2

4 to 2,5 P

10 to 6,3 P

The dimensions specified are approximately equal to

6,3 to 4P

–

4P

2,5 P

–

–

0,5 P

*) Including blind hole extension. 1)

e1 to be used where no other indications are made in product standards or on drawings.

2)

e2 to be used where a short extension is required for technical reasons.

3)

e3 to be used where a long extension is required for technical reasons.

4)

Type C to be used where no other indications are made in product standards or on drawings.

5)

Type D to be used where a short thread undercut is required for technical reasons.

In the case of fine pitch threads, the dimensions of thread run-outs and thread undercuts shall be selected as a function of the pitch. NOTE 1: The dimensions of thread run-outs and thread undercuts for pipe threads are specified in DIN 76-2, and those for trapezoidal threads, buttress threads, knuckle threads and other coarse pitch threads are specified in DIN 76-3. NOTE 2: For other types of screw thread (e.g. UNF threads), it is recommended that the relationships between thread run-outs (x or e values) and the pitch be used by analogy.