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Square U Bolts

Square U Bolts for Square & Rectangular Hollow Sections

Square bend U-bolts (square C-bolts) engineered for SHS and RHS tube, available in 304/316 stainless steel and carbon steel with zinc plated or hot-dip galvanised finishes.

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Square U bolts — also called square bend U-bolts or square C-bolts — are designed to clamp square and rectangular hollow sections (SHS/RHS) that round U-bolts cannot grip securely. Our square U-bolts cover box sections from 20×20 mm up to 300×150 mm, with three design options: standard leg length for square tube, extended leg length for rectangular tube, and extended width for spanning the long side of a rectangular section. All are manufactured from carbon steel, 304 or 316 stainless steel, or A320 L7 alloy steel, with rolled threads and supplied with hex nuts. Finishes include zinc plated, hot-dip galvanised and self colour. Rubber lined square C-bolts are available for vibration isolation and crevice corrosion protection. Custom sizes are manufactured to your drawing.

Square U Bolt Size Chart for Square Tube (Standard Leg, mm)

Box Section (mm) A – Inside Width (mm) Thread C – Leg Length (mm) D – Overall Height (mm)
20×20 21 M6 18 38
25×25 26 M6 18 43
30×30 31 M8 24 54
40×40 41 M10 30 70
50×50 51 M10 30 80
60×60 61 M10 30 90
70×70 72 M12 36 106
80×80 82 M12 36 116
100×100 102 M12 36 136
120×120 121 M12 36 156
150×150 151 M12 36 186

Square U Bolt Size Chart for Rectangular Tube (Extended Width, mm)

Box Section (mm) A – Inside Width (mm) Thread C – Leg Length (mm) D – Overall Height (mm)
40×20 41 M6 18 38
60×30 61 M8 24 54
80×40 81 M10 30 70
100×50 101 M10 30 80
140×70 141 M12 36 106
160×80 161 M12 36 116
200×100 201 M16 48 148
240×120 241 M16 48 168
300×150 301 M16 48 198

Extended-leg versions for rectangular tube available in all sizes. Custom dimensions on request.

Three Design Options

Standard Leg

Square tube clamping, compact fit

Extended Leg

For rectangular hollow sections and deeper clamping

Extended Width

Spans the long side of rectangular sections

Rubber Lined Square C-Bolt

Neoprene lined for insulation, vibration isolation and crevice corrosion protection

Materials & Finishes

304 stainless steel / 316 stainless steel for marine & chemical environments / carbon steel zinc plated / carbon steel hot-dip galvanised / self colour / A320 L7

Applications

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FAQ

What is the difference between a round U bolt and a square U bolt?

Round U bolts wrap cylindrical pipes, while square U bolts have a square bend radius that matches square and rectangular hollow sections (SHS/RHS) for full surface contact and secure clamping.

How do I choose standard leg or extended leg square U bolts?

Use standard leg for square tube clamped close to a flat surface; use extended leg when clamping rectangular tube or when extra clearance is needed for washers, nuts and backing plates.

What sizes of square tube do your square U bolts fit?

We cover box sections from 20×20 mm to 300×150 mm, with threads from M6 to M16 as standard.

Are stainless steel square U bolts available?

Yes, both 304 and 316 stainless steel square U bolts are available, with 316 recommended for outdoor, coastal and chemical environments.

Can square U bolts be custom made?

Yes. Provide your box section dimensions, leg length and material, and we will manufacture to your specification.

Clamping round pipes instead? Browse our Round U Bolts in M6–M24 for pipes NB 8–600 →

Need Square U Bolts in Custom Sizes?

Send us your box section dimensions, material and quantity — we reply within 24 hours.

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