Strongbox cold formed hollow sections
Specification details

EN-Construction-Product-Strongbox cold formed hollow sections | Key product features

Key product features

<p><strong>General hollow sections - Strongbox® 235</strong></p> <p>Key features</p> <ul> <li>Excellent quality, made with steel from a high quality production process</li> <li>Minimum strength of 235 MPa</li> <li>High levels of formability and, because the steel is fully-killed, excellent weldability</li> <li>Product subject to non-specific inspection and testing; with test report supplied</li> <li>Excellent consistent dimensional tolerances</li> <li>Excellent supply availability through approved stockholders</li> <li>Suitable for galvanising</li> </ul>

EN-Construction-Product-Tubes-Strongbox-Dimensional tolerancesTSE

Dimensional tolerances


 Circular Square/Rectangular 
Outside dimension (D B and H) ±1% with a min of ±0.50mm
and a max of ±10mm
Side length (mm)

H,B < 100

100 ≤ H,B

H,B > 200

±1% with a min of


Thickness (T) For D≤406.4mm
T ≤ 5mm ±10%
T > 5mm ±0.50mm

T ≤ 5mm
T > 5mm

± 10%
Out of roundness (O) 2% for D/T < 100, where
D/T ≥ 100 out-of-roundness

tolerance to be agreed
Concavity/Convexity (independent
tolerance on outside dimensions)
- Max 0.8% with a min of 0.5mm  
Squareness of side - 90º ± 1  
External corner profile
(radius need not be tangential to the
sides) EN10219: Part 2 Table 3
- T ≤ 6.0
6.0 < T ≤10.0
1.6T to 2.4T
2.0T to 3.0T
Twist (V) - 2mm plus 0.5mm/m length  

0.20% of total length &
3mm over any 1m length

0.15% of total length &
3mm over any 1m length
Mass (M) ±6% on individual
±6% on individual lengths ±6% on individual
Length -0 +50mm -0 +50mm -0 +50mm