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Round

Round
"
Not sure what size U bolt you have or need?
Two ways to confirm before you order - whichever you already know.
1If you have the pipe or tube

Measure the outside diameter of the pipe, tube or shaft, then pick a U bolt whose Inside Width (W) matches or just clears it. The W value is printed in every product name (e.g. '40mm Inside (W)'), and the Length (L) is the leg length that passes through your plate or bracket.

2If you have a U bolt in hand

Three numbers identify it: the inside width between the legs (measured across the straight section, not the bend), the leg length from the crown down, and the diameter across the thread. Our step-by-step guide shows all three with drawings.

Open the U bolt measuring guide ›

U bolt drawing showing the three measurements

About Round U Bolts

Round U Bolts are bolts bent into a U shape, with both legs threaded, used to clamp round pipe, tube, exhaust, leaf-spring or shaft hardware to a structure. The round bend matches the curve of the pipe so the clamp seats evenly without crushing the host.

Every Round U Bolt SKU on the BNA store ships as a pre-packed set with two matching nuts. Add flat washers for better load spread on softer host materials, or spring washers if the clamp is subject to vibration - match the washer finish to the U bolt finish to avoid galvanic pairing.

How to Measure

Three quick measurements identify any U bolt: inside width (W), leg length (L), then rod diameter and thread pitch.

Step 1 - Inside width (W) With the U bolt sitting on a flat surface, measure the gap between the inside faces of the two legs. Measure across the straight section of the legs, not at the bend - the bend reads a little wider. This is the maximum diameter of pipe, tube or shaft the U bolt will clamp around.

Step 2 - Leg length (L) Measure from the inside crown of the bend down to the end of one leg. This is the length of the U bolt that passes through the backing plate or bracket. Both legs are the same length - measure one. If the cut end is chamfered, measure to the last full thread for the working length.

Step 3 - Rod diameter and thread Measure the diameter of the rod across the unthreaded shank (not the threads - the thread crests sit slightly proud of the rod itself). Match the diameter to a metric size (M6, M8, M10, M12, M16, M20) or an imperial size (1/4", 5/16", 3/8" etc). The thread pitch follows the standard coarse pitch for that diameter (M10 is 1.5mm, M12 is 1.75mm) unless the part is marked otherwise.

Still not sure? See our step-by-step identification guide for help measuring your fastener.

Technical Resources

Every U bolt sub-category has its own CAD drawings and spec PDFs linked at the bottom of its page. For the full library covering U bolts and every other product range we stock, see our Technical PDFs library.

Frequently Asked Questions

What do Inside (W) and Length (L) mean?

Inside (W) is the gap between the two legs of the U bolt. Length (L) is the overall length from the top of the bend to the end of the threaded leg.

Match W to the outside diameter of the pipe being clamped, and L so the threaded ends pass through the backing plate with enough thread left to engage both nuts fully.

Is this suitable for outdoor or wet use?

Yes. Hot-dip galvanised round U bolts are the standard outdoor finish for exhaust, pipe-clamp, fence and structural use away from the coast. Stainless A4-70 G316 is the marine-grade choice within 300m of the sea.

Galvanising gives 20 to 50 years of outdoor service in dry rural and suburban environments. For coastal use, choose stainless A4-70 G316.

Material & Coating

Galvanised Hot-dip galvanised carbon steel. The standard outdoor finish; thick zinc coating gives decades of corrosion resistance. The right choice for trailer chassis, mast and pole mounting, structural pipe clamping and outdoor tank fittings.

Stainless A2-70 G304 - the standard stainless grade. Suits most external Australian environments. Used in food, dairy, mining and general outdoor work. A4-70 G316 (marine grade) adds 2-3% molybdenum to resist chloride attack within 300m of the coast.

Zinc Plated Bright silver electroplated zinc - interior use only. Suits protected industrial applications, indoor pipe clamping and machinery-frame use.

Matching finishes Always match the finish across the assembly. Hot-dip galvanising adds a much thicker coating than zinc plating, so a zinc-plated nut will not wind onto a galvanised bolt, and a galvanised nut on a zinc-plated bolt will be loose. Pair galvanised bolts with galvanised nuts and washers.

Browse our U bolts — Round · Square · Round with Plate · Matching Nuts · Matching Washers

Need help picking a U bolt? Tell us the inside width (W), leg length (L) and diameter you need - we'll match the right SKU. Contact us or call 07 3192 9800.

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Round U bolts for clamping round pipe, tube, exhaust, leaf-spring or shaft hardware. Every SKU ships as a pre-packed set with two matching nuts. Galvanised, zinc plated and stainless variants in M5 - M24 and BSW imperial.

TECHNICAL RESOURCES

Need help sizing your U bolt? See our U bolt measuring guide.

For the full library of charts and specs, see our Technical PDF's Library.

Filter by :
Filter By
Category
System of Measurement
  1. Metric 32 items
  2. Imperial 21 items
Size
  1. M10 (10mm) 13 items
  2. M12 (12mm) 11 items
  3. M16 (16mm) 1 item
  4. M20 (20mm) 4 items
  5. M24 (24mm) 3 items
  6. 1/4" 6 items
  7. 3/8" 8 items
  8. 1/2" 4 items
  9. 5/8" 1 item
  10. 3/4" 2 items
Size & Thread Pitch
  1. M10 x 1.50p Coarse 13 items
  2. M12 x 1.75p Coarse 11 items
  3. M16 x 2.00p Coarse 1 item
  4. M20 x 2.50p Coarse 4 items
  5. M24 x 3.00p Coarse 3 items
  6. 1/4" x 20 TPI BSW 6 items
  7. 3/8" x 16 TPI BSW 8 items
  8. 1/2" x 12 TPI BSW 4 items
  9. 5/8" x 11 TPI BSW 1 item
  10. 3/4" x 10 TPI BSW 2 items
Material / Finish
  1. Galvanised 33 items
  2. Stainless Steel 11 items
  3. Zinc Silver Plated 9 items
Class / Grade
  1. A4-70 G316 11 items
  2. Low Tensile Grade 2 21 items
  3. Low Tensile Class 4.6 21 items
Corrosion Protection Level
  1. Ultimate 11 items
  2. Excellent 33 items
  3. Moderate 9 items
Inside Width Range
  1. 20.00 - 29.00mm 8 items
  2. 30.00 - 39.00mm 5 items
  3. 40.00 - 49.00mm 6 items
  4. 50.00 - 59.00mm 3 items
  5. 60.00 - 79.00mm 7 items
  6. 80.00 - 99.00mm 4 items
  7. 100.00 - 119.00mm 5 items
  8. 120.00 - 199.00mm 4 items
  9. > 200.00mm 11 items
Overall Length From Inside
  1. 59.00 - 61.00mm 1 item
  2. 64.00 - 66.00mm 1 item
  3. 66.00 - 67.00mm 2 items
  4. 67.00 - 69.00mm 1 item
  5. 72.00 - 74.00mm 1 item
  6. 76.00 - 78.00mm 2 items
  7. 77.00 - 79.00mm 1 item
  8. 79.00 - 81.00mm 1 item
  9. 84.00 - 86.00mm 3 items
  10. 85.00 - 87.00mm 1 item
  11. 87.00 - 89.00mm 1 item
  12. 93.00 - 95.00mm 3 items
  13. 97.00 - 99.00mm 1 item
  14. 99.00 - 101.00mm 3 items
  15. 102.00 - 104.00mm 1 item
  16. 109.00 - 111.00mm 1 item
  17. 110.00 - 112.00mm 3 items
  18. 126.00 - 128.00mm 2 items
  19. 139.00 - 141.00mm 4 items
  20. 151.00 - 153.00mm 2 items
  21. 164.00 - 166.00mm 3 items
  22. 189.00 - 191.00mm 2 items
  23. 219.00 - 221.00mm 2 items
  24. 294.00 - 296.00mm 2 items
  25. 369.00 - 371.00mm 1 item
  26. 374.00 - 376.00mm 1 item
  27. 419.00 - 421.00mm 1 item
  28. 424.00 - 426.00mm 1 item
  29. 454.00 - 456.00mm 1 item
  30. 504.00 - 506.00mm 1 item
  31. 554.00 - 556.00mm 1 item
  32. 604.00 - 606.00mm 1 item
  33. 709.00 - 711.00mm 1 item
Nominal Bore
  1. 13mm (1/2") 1 item
  2. 15mm (9/16") 3 items
  3. 20mm (3/4") 4 items
  4. 25mm (1") 5 items
  5. 32mm (1-1/4") 4 items
  6. 40mm (1-9/16") 5 items
  7. 51mm (2") 5 items
  8. 65mm (2-9/16") 2 items
  9. 76mm (3") 2 items
  10. 80mm (3-1/4") 2 items
  11. 90mm (3-1/2") 2 items
  12. 101mm (4") 3 items
  13. 127mm (5") 2 items
  14. 150mm (6") 2 items
  15. 200mm (8") 2 items
  16. 250mm (10") 2 items
  17. 300mm (12") 2 items
  18. 350mm (13-3/4") 1 item
  19. 400mm (15-3/4") 1 item
  20. 450mm (17-3/4") 1 item
  21. 500mm (19-3/4") 1 item
  22. 600mm (23-3/4") 1 item
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