Structural Tension-Control Bolts Overview
Tension-control bolts, also called twist-off or TC bolts, are structural bolts whose spline breaks off at the designed tension. F1852 is A325 strength; F2280 is A490 strength.
How a TC bolt works
| Head | Round (button) head, no wrench flats |
|---|---|
| Tail | Spline end twists off at the designed installation tension |
| Tool | Electric shear wrench holds the spline and turns the nut |
| Supplied as | Bolt, nut and washer assembly from matched lots |
| Verification | Pre-installation testing per RCSC before use |
Strength
| Grade | Tensile (min) | Equivalent to |
|---|---|---|
| F1852 | 120 ksi | A325 |
| F2280 | 150 - 173 ksi | A490 |
These tables carry the same figures as the printed sheet below.
The printed sheet
See an error on this sheet?
Tell us what is wrong.
Text version of this sheet
ASTM F3125 · tension-control (TC) bolts overview
What it is
FIELD IDENTIFICATION
Tension-control bolts, also called twist-off or TC bolts, are structural bolts whose spline breaks off at
the designed tension. F1852 is A325 strength; F2280 is A490 strength.
MFG
A325
Round head, spline end twists off at tension
How a TC bolt works
Head
Round (button) head, no wrench flats
Tail
Spline end twists off at the designed installation tension
Tool
Electric shear wrench holds the spline and turns the nut
Supplied as
Bolt, nut and washer assembly from matched lots
Verification
Pre-installation testing per RCSC before use
Strength
Grade
Tensile (min)
Equivalent to
F1852
120 ksi
A325
F2280
150 - 173 ksi
A490
Key points
Spline gone means the bolt was tensioned with a TC wrench. A spline still on means it was not.
Lubrication and lot matching control whether the spline breaks at the right tension. Do not mix lots or re-lubricate in the field without the manufacturer.
Governing standards: ASTM F3125/F3125M-26; RCSC Specification. Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard always
take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-2BE4AF · thefastenerapp.com/fastener-guide/technical-reference/structural-tension-control-bolts-overview · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
