Tension Control Bolts
| Standard | EN 14399 · ASTM F1852 · F2280 |
|---|---|
| Material | 35CrMo / 40CrNiMo |
| Strength Grade | 10.9 / A325 |
| Size Range | M16-M30 |
| Surface Treatment | Hot Dip Galvanized / Zinc Flake |
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Product Description
Product Description & Key Specifications
Tension control bolts, also called TC bolts or twist-off bolts, are supplied for preloaded structural steel connections where installation tension is controlled by shearing the spline at the designed torque-tension condition. Materials include 35CrMo and 40CrNiMo with 10.9 / A325 project references.
Common standards include EN 14399 and ASTM F1852 / F2280 for structural bolting systems. TC bolt procurement should include bolt, nut and washer compatibility, lot control, lubrication condition, coating, storage, installation method and whether rotational capacity or system testing is required.
Hot-dip galvanized finish is widely used for bridge and outdoor steelwork, while zinc flake coating may be selected where controlled coating thickness and corrosion resistance are required. TC bolts should be installed with appropriate shear wrench equipment and project-approved procedures.
| Product type | Tension control bolts / TC bolts / twist-off bolts |
|---|---|
| Standards | EN 14399 / ASTM F1852 / ASTM F2280 |
| Material | 35CrMo / 40CrNiMo |
| Strength grade | 10.9 / A325 project reference |
| Size range | M16-M30 |
| Common models | M16 x 50, M20 x 70, M22 x 80, M24 x 90, M30 x 120 |
| Assembly form | Bolt, nut and washer set by structural bolting system |
| Surface finish | Hot-dip galvanized / Zinc flake |
| Documentation | MTC, CoC, lot traceability and system test reports on request |
Dimensions & SpecificationsEN 14399-10 TC Bolts
Technical Drawing
Dimensional Table
| Parameter | M12 | M16 | M20 | M22 | M24 | M27 | M30 | M36 |
|---|---|---|---|---|---|---|---|---|
| P | 1.75 | 2 | 2.5 | 2.5 | 3 | 3 | 3.5 | 4 |
| ds/max | 12.7 | 16.7 | 20.84 | 22.84 | 24.84 | 27.84 | 30.84 | 37 |
| ds/min | 11.3 | 15.3 | 19.16 | 21.16 | 23.16 | 26.16 | 29.16 | 35 |
| e/min | 23.91 | 29.56 | 35.03 | 39.55 | 45.2 | 50.85 | 55.37 | 66.44 |
| k/max | 7.95 | 10.75 | 13.4 | 14.9 | 15.9 | 17.9 | 19.75 | 23.55 |
| k/min | 7.05 | 9.25 | 11.6 | 13.1 | 14.1 | 16.1 | 17.65 | 21.45 |
| s/max | 22 | 27 | 32 | 36 | 41 | 46 | 50 | 60 |
| s/min | 21.16 | 26.16 | 31 | 35 | 40 | 45 | 49 | 58.8 |
| z/max | 16 | 18 | 20 | 21 | 21.5 | 24 | 26 | 31 |
| db/max | 8 | 11.6 | 14.4 | 15.7 | 17.1 | 19.3 | 21.4 | 25.7 |
| db/min | 7.4 | 11 | 13.8 | 15.1 | 16.5 | 18.7 | 20.8 | 25.1 |
| dc/min | 8.36 | 12.43 | 15.6 | 17.06 | 18.65 | 21.13 | 23.5 | 28.5 |
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Selection
Selection Advantages by Application
Bridge Steel Connections
M20, M22 and M24 TC bolts are commonly used in bridge splice plates and slip-critical steel connections where controlled preloading and installation verification are required.
Bridge fastenersHeavy Structural Frames
EN 14399 or ASTM F1852/F2280 TC bolt assemblies support high-strength steel frames where nut, washer and bolt lot compatibility matters. Confirm coating and lubrication condition.
Structural fastenersPower Generation Steelwork
Hot-dip galvanized or zinc flake TC bolts can be used for heavy equipment support structures and power plant steelwork where preloaded bolting systems are specified.
Power generation fasteners03
Assembly
Recommended Matching Products
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Manufacturing
Manufacturing & Quality Control
Manufacturing CapabilityQuality Control
Hot forging and spline forming for TC bolt geometryIncoming 35CrMo / 40CrNiMo material verification
Heat treatment and thread rolling by structural bolt gradeTensile, hardness and proof load checks by lot
HDG or zinc flake coating with assembly lubrication controlCoating thickness and nut fit inspection
Bolt-nut-washer system assembly packagingRotational capacity or tension test support when specified
Lot traceability for structural steel projectsMTC, CoC and inspection report prepared on request
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FAQ
Common Questions Before RFQ
What are tension control bolts?
Tension control bolts are structural bolts installed with a shear wrench. The spline twists off when the required installation condition is reached according to the bolting system design.
What is the difference between ASTM F1852 and F2280?
ASTM F1852 covers twist-off type tension control structural bolt/nut/washer assemblies comparable to A325 strength, while ASTM F2280 covers higher-strength assemblies comparable to A490 strength.
Can TC bolts be hot-dip galvanized?
Yes, HDG TC bolts are common for bridge and outdoor steelwork when the standard and assembly testing requirements allow it. Nut fit and lubrication condition must be controlled.
What sizes are commonly requested?
Common RFQ models include M16 x 50, M20 x 70, M22 x 80, M24 x 90 and M30 x 120. Final length should follow the steel connection drawing.
Are TC bolts supplied as assemblies?
Yes. TC bolts are normally supplied as compatible bolt, nut and washer assemblies with lot traceability and required test documentation.
Need EN 14399 or ASTM TC bolts?
Send your standard, diameter, length, grade, coating, assembly requirement, lot testing scope and quantity. Our team can quote TC bolt assemblies for bridge and heavy steel projects.
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