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U Bolts

U Bolts
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.

U bolt drawing showing the three measurements

U Bolts for Pipe, Tube, Exhaust and Trailer Clamping

U Bolts are a U-shaped fastener with two threaded legs, supplied as a kit with matching nuts (and on some kits, washers and a backing plate). The U-shape wraps around the work piece - round pipe, mast, exhaust, square section or shaft - and is secured with nuts on the threaded ends through a backing plate or bracket.

Bolt & Nut Australia stocks 114+ U bolt variants from our Brisbane warehouse across three profiles - Round, Square and Round with Plate. Available in galvanised, stainless A2-70 G304, stainless A4-70 G316 marine, and zinc plated. Metric coarse (M5 - M24) and BSW imperial (1/4" - 3/4") threads.

Browse by Profile

Round U Bolts - curved bend for round pipe, tube, exhaust, leaf-spring or shaft hardware. Supplied with two matching nuts. Galvanised, zinc plated and stainless variants stocked in M5 to M24 and BSW imperial.

Square U Bolts - 90-degree bend for square / rectangular hollow section, angle and structural framing. Supplied with two nuts plus washers (nyloc + flat washers on most SKUs, hex + spring on the rest).

Round U Bolts with Plate - complete pipe-clamp sets in stainless A2-70 G304. Includes the round U bolt, two hex nuts, two washers, a pre-drilled mounting plate and two crimps (curved saddles that stop the plate sliding down the pipe). Made to the Inox World Standard.

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 PDF's 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 or section being clamped, and L so the threaded ends pass through the backing plate or bracket with enough thread left to engage both nuts fully.

Round or Square: which do I need?

Match the U bolt shape to the host section. Round U bolts clamp round pipe, tube, exhaust or shaft. Square U bolts clamp square or rectangular hollow section (RHS / SHS) or angle.

Using a Round U bolt on a square section gives only two narrow contact lines and over-tightening crushes the corners. Using a Square U bolt on round pipe leaves four-point contact and pinches the pipe. Pick the shape that fits the host section flush.

Is this suitable for outdoor or wet use?

Yes. Hot-dip galvanised 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.

Hot-dip galvanising gives 20 to 50 years of outdoor service in dry rural and suburban environments. For coastal use, the molybdenum content in A4 grade resists pitting in seawater spray.

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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114+ U bolt and nut kits from our Brisbane warehouse - round, square and round-with-plate profiles, in galvanised, stainless A2-70 G304, A4-70 G316 marine, and zinc plated. Metric coarse (M5 - M24) and BSW imperial threads. Same-day dispatch on stocked SKUs.

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 59 items
  2. Imperial 54 items
Size
  1. M5 (5mm) 1 item
  2. M6 (6mm) 1 item
  3. M8 (8mm) 2 items
  4. M10 (10mm) 18 items
  5. M12 (12mm) 29 items
  6. M16 (16mm) 1 item
  7. M20 (20mm) 4 items
  8. M24 (24mm) 3 items
  9. 1/4" 6 items
  10. 3/8" 8 items
  11. 1/2" 37 items
  12. 5/8" 1 item
  13. 3/4" 2 items
Size & Thread Pitch
  1. M5 x 0.80p Coarse 1 item
  2. M6 x 1.00p Coarse 1 item
  3. M8 x 1.25p Coarse 2 items
  4. M10 x 1.50p Coarse 18 items
  5. M12 x 1.75p Coarse 29 items
  6. M16 x 2.00p Coarse 1 item
  7. M20 x 2.50p Coarse 4 items
  8. M24 x 3.00p Coarse 3 items
  9. 1/4" x 20 TPI BSW 6 items
  10. 3/8" x 16 TPI BSW 8 items
  11. 1/2" x 12 TPI BSW 37 items
  12. 5/8" x 11 TPI BSW 1 item
  13. 3/4" x 10 TPI BSW 2 items
Thread Type
  1. Metric - Coarse 59 items
  2. BSW - Coarse 54 items
Material / Finish
  1. Galvanised 78 items
  2. Stainless Steel 26 items
  3. Zinc Silver Plated 9 items
Class / Grade
  1. A2-70 G304 7 items
  2. A4-70 G316 19 items
  3. Low Tensile Grade 2 54 items
  4. Low Tensile Class 4.6 33 items
Corrosion Protection Level
  1. Ultimate 19 items
  2. Excellent 85 items
  3. Moderate 9 items
Inside Width Range
  1. 20.00 - 29.00mm 11 items
  2. 30.00 - 39.00mm 7 items
  3. 40.00 - 49.00mm 25 items
  4. 50.00 - 59.00mm 25 items
  5. 60.00 - 79.00mm 17 items
  6. 80.00 - 99.00mm 4 items
  7. 100.00 - 119.00mm 8 items
  8. 120.00 - 199.00mm 5 items
  9. > 200.00mm 11 items
Overall Length From Inside
  1. 59.00 - 61.00mm 2 items
  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 2 items
  6. 74.00 - 76.00mm 4 items
  7. 76.00 - 78.00mm 2 items
  8. 77.00 - 79.00mm 1 item
  9. 79.00 - 81.00mm 5 items
  10. 84.00 - 86.00mm 5 items
  11. 85.00 - 87.00mm 3 items
  12. 87.00 - 89.00mm 1 item
  13. 89.00 - 91.00mm 2 items
  14. 93.00 - 95.00mm 4 items
  15. 97.00 - 99.00mm 1 item
  16. 99.00 - 101.00mm 8 items
  17. 102.00 - 104.00mm 1 item
  18. 109.00 - 111.00mm 6 items
  19. 110.00 - 112.00mm 3 items
  20. 111.00 - 113.00mm 4 items
  21. 114.00 - 116.00mm 1 item
  22. 124.00 - 126.00mm 7 items
  23. 126.00 - 128.00mm 2 items
  24. 136.00 - 138.00mm 4 items
  25. 139.00 - 141.00mm 5 items
  26. 144.00 - 146.00mm 2 items
  27. 149.00 - 151.00mm 4 items
  28. 151.00 - 153.00mm 2 items
  29. 159.00 - 161.00mm 1 item
  30. 161.00 - 163.00mm 3 items
  31. 164.00 - 166.00mm 5 items
  32. 174.00 - 176.00mm 2 items
  33. 189.00 - 191.00mm 2 items
  34. 199.00 - 201.00mm 1 item
  35. 219.00 - 221.00mm 2 items
  36. 249.00 - 251.00mm 1 item
  37. 294.00 - 296.00mm 2 items
  38. 369.00 - 371.00mm 1 item
  39. 374.00 - 376.00mm 1 item
  40. 419.00 - 421.00mm 1 item
  41. 424.00 - 426.00mm 1 item
  42. 454.00 - 456.00mm 1 item
  43. 504.00 - 506.00mm 1 item
  44. 554.00 - 556.00mm 1 item
  45. 604.00 - 606.00mm 1 item
  46. 709.00 - 711.00mm 1 item
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