Westfield Fasteners Product Specification:

DIN 603 - Coach Bolts (Cup Head Square Neck Bolts), with Part Thread

This product guide contains the specification for metric threaded coach bolts / carriage bolts, specifically with a part threaded shank, available from Westfield Fasteners. The basis of this specification is the DIN standard DIN 603.

Product Description

Generally used in timber to timber and timber to metal construction, these bolts incorporate a square neck to grip the hole in the timber when fitting, and therefore negates the need for any drive recess to be included on top of the head. Supplied to DIN 603, but with a partially threaded shank.

Scope of the ISO standard.

DIN 603 specifies the tolerances and the permissable variation in form of carriage bolts / coach bolts / cup head bolts, and covers metric thread diameters from M5 up to and including M20. Mechanical properties for these items are defined in ISO 898 and ISO 3506.

Table 1 below defines the overall dimensions and tolerances of this screw type, whilst table 2 defines the tolerances on the shank length.

Notes to figure 1:

There may be up to 2 incomplete threads at the end of the bolt (a).

Variations from DIN 603

In practice, the manufacturers often stray away from the standard when deciding how much thread to apply to the shank on these bolts. This is why there are fully threaded variants of many available sizes. With this in mind, the data provided in table 2 should be taken as a guide only.

Table 1: Dimensions & Tolerances according to DIN 603

Thread, d	M5	M6	M8	M10	M12	M16	M20
thread pitch (standard metric coarse)	0.8	1	1.25	1.5	1.75	2	2.5
thread length	b min. (shank length ≤ 125mm)	16	18	22	26	30	38	46
b min. (shank length > 125mm ≤ 200mm)	22	24	28	32	36	44	52
b min. (shank length > 200mm)	-	-	41	45	49	57	65
head diameter	d_k max.	13.55	16.55	20.65	24.65	30.65	38.80	46.80
d_k min.	12.45	15.45	19.35	23.35	29.35	37.20	45.20
shank diameter	d_s max.	5	6	8	10	12	16	20
d_s min.	4.52	5.52	7.42	9.42	11.30	15.30	19.16
neck height	f_n max.	4.10	4.60	5.60	6.60	8.75	12.90	15.90
f_n min.	2.90	3.40	4.40	5.40	7.25	11.10	14.10
head height	k max.	3.30	3.88	4.88	5.38	6.95	8.95	11.05
k min.	2.70	3.12	4.12	4.65	6.05	8.05	9.95
head radius	r₁ ≈ (approx.)	10.7	12.6	16	19.2	24.1	29.3	33.9
neck radius	r₂ max.	0.5	0.5	0.5	0.5	1.0	1.0	1.0
square neck radius	r₃ max.	0.75	0.90	1.20	1.50	1.80	2.40	3.0*
neck thickness	v_n max.	5.48	6.48	8.58	10.58	12.70	16.70	20.84
v_n min.	4.52	5.52	7.42	9.42	11.30	15.30	19.16

Thread, d

M10

M12

M16

M20

thread pitch (standard metric coarse)

0.8

1.25

1.5

1.75

2.5

thread length

b min. (shank length ≤ 125mm)

b min. (shank length > 125mm ≤ 200mm)

b min. (shank length > 200mm)

head diameter

d_k max.

13.55

16.55

20.65

24.65

30.65

38.80

46.80

d_k min.

12.45

15.45

19.35

23.35

29.35

37.20

45.20

shank diameter

d_s max.

d_s min.

4.52

5.52

7.42

9.42

11.30

15.30

19.16

neck height

f_n max.

4.10

4.60

5.60

6.60

8.75

12.90

15.90

f_n min.

2.90

3.40

4.40

5.40

7.25

11.10

14.10

head height

k max.

3.30

3.88

4.88

5.38

6.95

8.95

11.05

k min.

2.70

3.12

4.12

4.65

6.05

8.05

9.95

head radius

r₁ ≈ (approx.)

10.7

12.6

19.2

24.1

29.3

33.9

neck radius

r₂ max.

0.5

1.0

square neck radius

r₃ max.

0.75

0.90

1.20

1.50

1.80

2.40

3.0*

neck thickness

v_n max.

5.48

6.48

8.58

10.58

12.70

16.70

20.84

v_n min.

4.52

5.52

7.42

9.42

11.30

15.30

19.16

Table 2: Shank Length Tolerance according to DIN 603

total shank length	M5	M6	M8	M10	M12	M16	M20
unthreaded shank length (l_s) and distance from head to first full form thread profile(l_g)
Nom. size	min	max	l_s min	l_g max	l_s min	l_g max	l_s min	l_g max	l_s min	l_g max	l_s min	l_g max	l_s min	l_g max	l_s min	l_g max
16	15.10	16.90	-	8	-	10	/	/	/	/	/	/	/	/	/	/
20	18.95	21.05	-	8	-	10	-	12	-	14	/	/	/	/	/	/
25	23.95	26.05	-	8	-	10	-	12	-	14	/	/	/	/	/	/
30	28.95	31.05	-	18	-	10	-	12	-	14	-	18	/	/	/	/
35	33.75	36.25	15	19	12	17	-	12	-	14	-	18	/	/	/	/
40	38.75	41.25	20	24	17	22	11.75	18	-	14	-	18	/	/	/	/
45	43.75	46.25	25	29	22	27	16.75	23	11.5	19	-	18	/	/	/	/
50	48.75	51.25	30	34	27	32	21.75	28	16.5	24	-	18	/	/	/	/
55	53.50	56.50	35	39	32	37	26.75	33	21.5	29	16.25	25	-	23	/	/
60	58.50	61.50	40	44	37	42	31.75	38	26.5	34	21.25	30	-	23	/	/
65	63.50	66.50	45	49	42	47	36.75	43	31.5	39	26.75	35	17	27	/	/
70	68.50	71.50	50	54	47	52	41.75	48	36.5	44	31.25	40	22	32	-	28.5
80	78.50	81.50	60	64	57	62	51.75	58	46.5	54	41.25	50	32	42	21.5	34
90	88.25	91.75	-	-	67	72	61.75	68	56.5	64	51.25	60	42	52	31.5	44
100	98.25	101.75	-	-	77	82	71.75	78	66.5	74	61.25	70	52	62	41.5	54
110	108.25	111.75	-	-	87	92	81.75	88	76.5	84	71.25	80	62	72	51.5	64
120	118.25	121.75	-	-	97	102	91.75	98	86.5	94	81.25	90	72	82	61.5	74
130	128.00	132.00	-	-	101	106	95.75	102	90.5	98	85.25	94	76	86	65.5	78
140	138.00	142.00	-	-	111	116	105.75	112	100.5	108	95.25	104	86	96	75.5	88
150	148.00	152.00	-	-	121	126	115.75	122	110.5	118	105.25	114	96	106	85.5	98
160	156.00	164.00	-	-	-	-	-	-	120.5	128	115.25	124	106	116	95.5	108
180	176.00	184.00	-	-	-	-	-	-	140.5	148	135.25	144	126	136	115.5	128
200	195.40	204.60	-	-	-	-	-	-	160.5	168	155.25	164	146	156	135.5	148

total shank length

M10

M12

M16

M20

unthreaded shank length (l_s) and distance from head to first full form thread profile(l_g)

Nom. size

min

max

l_s min

l_g max

l_s min

l_g max

l_s min

l_g max

l_s min

l_g max

l_s min

l_g max

l_s min

l_g max

l_s min

l_g max

15.10

16.90

18.95

21.05

23.95

26.05

28.95

31.05

33.75

36.25

38.75

41.25

11.75

43.75

46.25

16.75

11.5

48.75

51.25

21.75

16.5

53.50

56.50

26.75

21.5

16.25

58.50

61.50

31.75

26.5

21.25

63.50

66.50

36.75

31.5

26.75

68.50

71.50

41.75

36.5

31.25

28.5

78.50

81.50

51.75

46.5

41.25

21.5

88.25

91.75

61.75

56.5

51.25

31.5

100

98.25

101.75

71.75

66.5

61.25

41.5

110

108.25

111.75

81.75

76.5

71.25

51.5

120

118.25

121.75

102

91.75

86.5

81.25

61.5

130

128.00

132.00

101

106

95.75

102

90.5

85.25

65.5

140

138.00

142.00

111

116

105.75

112

100.5

108

95.25

104

75.5

150

148.00

152.00

121

126

115.75

122

110.5

118

105.25

114

106

85.5

160

156.00

164.00

120.5

128

115.25

124

106

116

95.5

108

180

176.00

184.00

140.5

148

135.25

144

126

136

115.5

128

200

195.40

204.60

160.5

168

155.25

164

146

156

135.5

148

DIN 603 - Coach Bolts (Cup Head Square Neck Bolts), with Part Thread

Figure 1: Coach Bolts with part thread

Notes to figure 1:

Table 1: Dimensions & Tolerances according to DIN 603

Table 2: Shank Length Tolerance according to DIN 603