ASME B18.2.6:2019 High Strength Tension Control Button Head Bolt is suitable for structural joints that need high preload while also requiring a low-protrusion, smooth head profile. The button head reduces external interference and improves local clearance.
The tension-control installation method supports more stable preload control in steel structures, bridge components, equipment supports, and space-limited high-strength nodes. Compared with hex head styles, the button head offers advantages in appearance and clearance.
It should be used with appropriate installation tools, nuts, and washers. Batch consistency, friction-surface condition, and final tightening inspection are important, especially for safety-related structural applications.

Dimensions unit: mm
| Thread size | 1/2 | 5/8 | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | ||||
| PP | UNC | 13 | 11 | 10 | 9 | 8 | 7 | 7 | |||
| k | Max. | 0.323 | 0.403 | 0.483 | 0.563 | 0.627 | 0.718 | 0.813 | |||
| Min. | 0.302 | 0.378 | 0.455 | 0.531 | 0.591 | 0.658 | 0.749 | ||||
| ds | Max. | 0.515 | 0.642 | 0.768 | 0.895 | 1.022 | 1.149 | 1.277 | |||
| Min. | 0.482 | 0.605 | 0.729 | 0.852 | 0.976 | 1.098 | 1.223 | ||||
| dk | Max. | 1.126 | 1.313 | 1.58 | 1.88 | 2.158 | 2.375 | 2.76 | |||
| b | Thread length | Reference value | 1 | 1.25 | 1.38 | 1.5 | 1.75 | 2 | 2 | ||
| z | Reference value | 0.5 | 0.6 | 0.65 | 0.72 | 0.8 | 0.9 | 1 | |||
| s1 | Reference value | 0.32 | 0.43 | 0.53 | 0.61 | 0.7 | 0.8 | 0.9 | |||
① Material and mechanical properties should meet the requirements of ASTM F 1852 or ASTM F 2280.
② ASTM A325/A325M/A490/A490M/F1852/F2280 has been merged into ASTM F3125
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