Tension Control Bolts (TC Bolts) – High-Strength Structural Fasteners for Steel Connections
Tension control bolts, often referred to as TC bolts or twist-off bolts, are high-strength fasteners covered under the ASTM F3125 specification for structural bolts. They are manufactured in two grades:
ASTM F3125 Grade F1852 – equivalent in strength to A325 structural bolts.
ASTM F3125 Grade F2280 – equivalent in strength to A490 structural bolts.
These bolts are widely used in bridges, steel buildings, stadiums, and other infrastructure projects where high-strength, consistent connections are essential. These high-strength fasteners are available in both plain finish and hot-dip galvanized to meet your requirements.
TC Bolts Installation
TC bolts feature a spline that shears off when the proper tension is achieved. Using a specialized shear wrench, the bolt automatically tightens until the spline twists off, providing a clear visual indication that the correct preload has been reached. This system:
Improves installation speed and consistency.
Ensures reliable performance in critical structural steel connections.
Advantages of TC Bolts
Consistent tensioning: Accurate and repeatable preload on every installation.
Faster installation: Reduced labor time compared to calibrated wrench methods.
Mechanical Properties of TC Bolts
The mechanical properties of tension control bolts are those identified in the ASTM F3125 specification, as this is the specification that covers tension control bolts.
| Grade | Tensile, ksi | Yield, ksi min | Elongation, % min | RA, % min |
|---|---|---|---|---|
| 120ksi (A325/F1852) | 120 min | 92 | 14 | 35 |
| 144ksi (F3148) | 144 min | 115 | 14 | 35 |
| 150ksi (A490/F2280) | 150-173 | 130 | 14 | 40 |
Permitted Coatings of TC Bolts
Permitted coatings for tension control bolts are also outlined in the specification ASTM F3125, as the following chart indicates.
| 120 ksi/830 Mpa and 144 ksi Bolt Assemblies* | |||
|---|---|---|---|
| Commonly Applied Coatings | Grade or Class | ||
| F2329 | Hot Dip Galvanized / 50 μm | ||
| B695 | Class 55 | ||
| Other Coatings | Classification codes | ||
| Corrosion | Appearance | Coefficient of friction | |
| F3393 | D | 1 | R** |
| 150 ksi/1040 Mpa Bolt Assemblies* | |||
|---|---|---|---|
| Qualified Coatings | Classification codes | ||
| Corrosion | Appearance | Coefficient of friction | |
| F3393 | D | 1 | R** |
* Coatings for Twist-Off style bolt assemblies shall be agreed upon between the producer, supplier and user, and are not permitted except when applied under the direction of the manufacturer. The coefficient of friction classification code does not apply to Twist-Off style bolt assemblies.
** Specification F3393 is a consolidation and replacement of three ASTM standards which included qualified coatings F1136/F1136M Bolt & Washer Grade 3, Nut Grade 5, F2833 Grade 1, and F3019/F3019M Grade 4.
Our TC Bolt Stock
| Item ID | Item Description | Finish | Grade |
|---|---|---|---|
| 62C200BTC3 | 5/8" X 2" | Plain | F1852 |
| 75C175BTC3M | 3/4" X 1-3/4" | Galvanized | F1852 |
| 75C200BTC3M | 3/4" X 2" | Galvanized | F1852 |
| 75C225BTC3M | 3/4" X 2-1/4 | Galvanized | F1852 |
| 75C450BTC3M | 3/4" X 4-1/2 | Galvanized | F1852 |
| 87C200BTC3 | 7/8" X 2" | Plain | F1852 |
| 87C200BTC3M | 7/8" X 2" | Galvanized | F1852 |
| 87C225BTC3 | 7/8" X 2-1/4 | Plain | F1852 |
| 87C250BTC3 | 7/8" X 2 1/2 | Plain | F1852 |
| 87C275BTC3 | 7/8" X 2-3/4" | Plain | F1852 |
| 87C275BTC3M | 7/8" X 2-3/4" | Galvanized | F1852 |
| 87C300BTC3M | 7/8" X 3" | Galvanized | F1852 |
| 87C325BTC3 | 7/8" X 3-1/4" | Plain | F1852 |
| 87C325BTC3M | 7/8" X 3-1/4" | Galvanized | F1852 |
| 87C350BTC3M | 7/8" X 3-1/2" | Galvanized | F1852 |
| 87C375BTC3M | 7/8" X 3-3/4" | Galvanized | F1852 |
| 87C400BTC3M | 7/8" X 4" | Galvanized | F1852 |
| 87C450BTC3 | 7/8" X 4-1/2 | Plain | F1852 |
| 87C475BTC3 | 7/8" X 4-3/4" | Plain | F1852 |
| 87C500BTC3 | 7/8" X 5 | Plain | F1852 |
| 87C550BTC3 | 7/8" X 5-1/2 | Plain | F1852 |
| 87C600BTC3 | 7/8" X 6 | Plain | F1852 |
| 112C275BTC3M | 1-1/8" X 2-3/4" | Galvanized | F1852 |
| 112C275BTC4 | 1-1/8" X 2-3/4" | Plain | F2280 |
| 112C300BTC3M | 1-1/8" X 3" | Galvanized | F1852 |
| 112C300BTC4 | 1-1/8" X 3" | Plain | F2280 |
| 112C325BTC3M | 1-1/8" X 3-1/4" | Galvanized | F1852 |
| 112C325BTC4 | 1-1/8" X 3-1/4" | Plain | F2280 |
| 112C350BTC3M | 1-1/8 X 3-1/2" | Galvanized | F1852 |
| 112C350BTC4 | 1-1/8" X 3-1/2" | Plain | F2280 |
| 112C375BTC4 | 1-1/8" X 3-3/4" | Plain | F2280 |
| 112C400BTC3M | 1-1/8" X 4" | Galvanized | F1852 |
| 112C425BTC3M | 1-1/8" X 4-1/4" | Galvanized | F1852 |
| 112C475BTC3M | 1-1/8" X 4-3/4" | Galvanized | F1852 |
| 112C500BTC3M | 1-1/8" X 5" | Galvanized | F1852 |
| 112C600BTC4 | 1-1/8" X 6" | Plain | F2280 |
| 112C650BTC4 | 1-1/8" X 6-1/2" | Plain | F2280 |
| 112C700BTC4 | 1-1/8" X 7" | Plain | F2280 |
| 112C750BTC4 | 1-1/8" X 7-1/2" | Plain | F2280 |
| 112C800BTC4 | 1-1/8" X 8" | Plain | F2280 |
| 112C850BTC4 | 1-1/8" X 8-1/2" | Plain | F2280 |
| 112C900BTC4 | 1-1/8 X 9" | Plain | F2280 |
| 112C950BTC4 | 1-1/8 X 9-1/2" | Plain | F2280 |