Carriage Bolt DIN 603
Equivalent Standard: ISO 8677 | UNI 5731
Carriage Bolt DIN 603 is a round Head Bolt with Square Neck underneath. The Square neck Beneath Round head act as a locking neck, which prevents turning when the nut is tightened or removed ensuring a secure and robust connection.
Typical Applications:
The square neck locks into wood or metal, preventing the bolt from turning when a nut is tightened. Round head provides a smooth, tamper-resistant surface Finish, often used where aesthetics or safety is important. The Square Neck provides resistance while turning when the nut is tightened.
Other Common uses include:
- Commonly used for Fastening wood to wood, wood to metal, or metal to metal (often where access to the bolt head is limited or undesirable after installation).
- Timber construction and woodworking (e.g., decking, fencing, garden furniture, playground equipment)
- Security fixings (as they are difficult to undo from the head side)
- Joining metal components where a self-locking bolt is beneficial.
Nuts and Washers Compatibility with DIN 603 bolts:
- DIN 934 (Hex nuts)
- DIN 125 or DIN 9021 (Flat washers, for load distribution)
- DIN 603
- Material Grade: 4.8, 8.8
- Size: M5 to M20
- Finish: Bright ZINC, HOT DIP Galvanization. Self Black Oxide.
- Thread: METRIC
DIN 603
DIN 603 specifies the tolerances and the permissable variation in form of carriage bolts / coach bolts / cup head bolts. Din 603 is Round Head With Square neck unerneath is specially used for fasting metal to wood. Din 603 bolt or Carriage bolts have a smooth head which is not easily accessed for fastening and Square neck prevents the bolt from turning when the nut is tightened which differentiates these din 603 standard bolts from regular bolts. Din 603 carriage bolts have special type of head which adds a finished or decorative look to any application distributing the load on wider clamping area. Diameters ranging from M5 to M20 and lengths up to 80mm.
Technical Specification for DIN 603 Carriage Bolts with Mushroom Round Head
| Thread d | M5 | M6 | M8 | M10 | M12 | M16 | M20 | |
| P | 0,8 | 1 | 1,25 | 1,5 | 1,75 | 2 | 2,5 | |
| b | l < 125mm | 16 | 18 | 22 | 26 | 30 | 38 | 46 |
| 125 < l < 200mm | 22 | 24 | 28 | 32 | 36 | 44 | 52 | |
| l > 200mm | – | – | 41 | 45 | 49 | 57 | 65 | |
| dk | max. | 13,55 | 16,55 | 20,65 | 24,65 | 30,65 | 38,8 | 46,8 |
| min. | 12,45 | 15,45 | 19,35 | 23,35 | 29,35 | 37,2 | 45,2 | |
| ds | max. | 5 | 6 | 8 | 10 | 12 | 16 | 20 |
| min. | 4,52 | 5,52 | 7,42 | 9,42 | 11,3 | 15,3 | 19,16 | |
| f | max. | 4,1 | 4,6 | 5,6 | 6,6 | 8,75 | 12,9 | 15,9 |
| min. | 2,9 | 3,4 | 4,4 | 5,4 | 7,25 | 11,1 | 14,1 | |
| k | max. | 3,3 | 3,88 | 4,88 | 5,38 | 6,95 | 8,95 | 11,05 |
| min. | 2,7 | 3,12 | 4,12 | 4,62 | 6,05 | 8,05 | 9,95 | |
| r1 | approx. | 10,7 | 12,6 | 16 | 19,2 | 24,1 | 29,3 | 33,9 |
| r2 | max. | 0,5 | 0,5 | 0,5 | 0,5 | 1 | 1 | 1 |
| r3 | max. | 0,75 | 0,9 | 1,2 | 1,5 | 1,8 | 2,4 | 3 |
| v | max. | 5,48 | 6,48 | 8,58 | 10,58 | 12,7 | 16,7 | 20,84 |
| min. | 4,52 | 5,52 | 7,42 | 9,42 | 11,3 | 15,3 | 19,16 | |
| l | M5 | M6 | M8 | M10 | M12 | M16 | M20 | |||||||||
| nominal size | min. | max. | ls min. | lg max. | ls min. | lg max. | ls min. | lg max. | ls min. | lg max. | ls min. | lg max. | ls min. | lg max. | ls min. | lg max. |
| 16 | 15,1 | 16,9 | – | 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 | 53,5 | 56,5 | 35 | 39 | 32 | 37 | 26,75 | 33 | 21,5 | 29 | 16,25 | 25 | – | 23 | ||
| 60 | 58,5 | 61,5 | 40 | 44 | 37 | 42 | 31,75 | 38 | 26,5 | 34 | 21,25 | 30 | – | 23 | ||
| 65 | 63,5 | 66,5 | 45 | 49 | 42 | 47 | 36,75 | 43 | 31,5 | 39 | 26,75 | 35 | 17 | 27 | ||
| 70 | 68,5 | 71,5 | 50 | 54 | 47 | 52 | 41,75 | 48 | 36,5 | 44 | 31,25 | 40 | 22 | 32 | – | 28,5 |
| 80 | 78,5 | 81,5 | 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 | 132 | 101 | 106 | 95,75 | 102 | 90,5 | 98 | 85,25 | 94 | 76 | 86 | 65,5 | 78 | ||
| 140 | 138 | 142 | 111 | 116 | 105,75 | 112 | 108,5 | 108 | 95,25 | 104 | 86 | 96 | 75,5 | 8 | ||
| 150 | 148 | 152 | 121 | 126 | 115,75 | 122 | 110,5 | 118 | 105,25 | 114 | 96 | 106 | 85,5 | 98 | ||
| 160 | 156 | 164 | 120,5 | 128 | 115,25 | 124 | 106 | 116 | 95,5 | 108 | ||||||
| 180 | 176 | 184 | 140,5 | 148 | 135,25 | 144 | 126 | 136 | 115,5 | 128 | ||||||
| 200 | 195,4 | 204,6 | 160,5 | 168 | 155,25 | 164 | 146 | 156 | 135,5 | 148 | ||||||
ISO Equivalent: Superseded by ISO 8677 in many countries still DIN 603 is more popular & extensively used in practice, and parts are readily available from many suppliers. There can be minor dimensional differences between DIN 603 and ISO 8677, so it’s always advisable to check the specific product data sheet if exact dimensions are critical. DIN 603 valued for its self-locking feature and smooth head design, making it suitable for a broad range of construction, woodworking, and assembly applications.