U Bolt Size Chart for Pipes: DN15 to DN300 in mm

This U bolt size chart lists steel pipes from DN15 to DN300 with the outside diameter in mm and the U bolt that fits each one: thread size, inside width, leg centres, height and thread length. A nominal pipe size does not give the outside diameter, so the chart starts from the real one.

The pipe outside diameters are the ISO 4200 series 1 values (also the EN 10220 sizes), listed by DN number (ISO 6708); the U bolt sizes follow DIN 3570. Confirm each size against your drawing.

How a U Bolt Is Measured

A U bolt, also sold as a pipe clamp U bolt, is a rod bent into a U with a thread on each leg. DIN 3570 names its sizes with five letters. The inside width a must match the outside diameter of the pipe, not the nominal bore, and the rod diameter d is the thread size: an M12 U bolt is bent from 12 mm rod.

The leg centres e set the hole spacing in the plate: inside width plus one rod diameter, 64 + 12 = 76 mm on the DN50 size. The height h runs from the outside of the bend to the leg ends, and b is the thread length. The DIN 3570 drawing shows a 10 mm plate with a nut above and below it.

U Bolt Size Chart for Steel Pipes, DN15 to DN300

Rows DN20 to DN300 are DIN 3570 sizes, read from the tables of Westfield Fasteners, fasten.it and fasteners.eu, reconciled where one has a misprint. The standard covers nominal widths of 20 to 500 mm, the same numbers as DN, with threads from M10 to M24.

How to read the chart: all sizes in mm. DN15 is below the DIN 3570 range: its 23 mm width is a commercial size in M8 or M10, and suppliers disagree on height and thread length, so those cells are blank. Most widths are listed for two tubes, 64 mm for 57 and 60.3 mm for example, so a 60.3 mm pipe has under 2 mm of play each side. Thread length b is the DIN 3570 value (fasteners.eu lists it as a minimum).

U Bolt Thread Size by Pipe OD

The U bolt thread size steps up with the pipe diameter. The bands below come from the chart, with the coarse pitch of each thread from our metric thread pitch chart (ISO 261).

Why a 2 Inch Pipe Is 60.3 mm

Pipe sizes are names, not measurements. A 2 inch pipe, also written DN50 or 50 NB, is 60.3 mm outside in the ISO series, IS 1239 and ASME B36.10, because the 2 inch label once described the bore.

Two systems differ slightly. ASME pipe is 26.7, 33.4 and 42.2 mm at 3/4, 1 and 1 1/4 inch and still fits the 30, 38 and 46 mm widths, each listed for two tubes; the 73.0 mm 2 1/2 inch pipe sits in the 82 mm width with 4.5 mm of play each side. IS 1239 gives bands, 59.7 to 60.8 mm for 50 NB, and its 150 NB tube is 163.9 to 166.5 mm, not 168.3 mm; the 176 mm width covers 159 to 168.3 mm tubes, so both fit.

How to Order a U Bolt

Send three numbers and three words: thread x inside width x height, plus the thread length if your plate is thick; then material, grade and finish. Say whether you want nuts and washers. If you only know the pipe size, give that; for square sections, cables and rods, give the outside size of the part.

Example: U bolt M12 x 64 x 109 to DIN 3570 for DN50 pipe, mild steel 4.6, hot dip galvanized, with 2 hex nuts and 2 washers each, quantity 200. An M12 nut takes an 18 mm spanner (19 mm for DIN nuts); see our spanner size chart.

Material and Finish

Mild steel 4.6 or 5.6 is the usual grade for pipe supports, hot dip galvanized or zinc plated outdoors. High tensile 8.8 and 10.9 U bolts do heavy clamping such as vehicle leaf springs. SS 304 and SS 316 suit chemical, food and coastal sites, and SS 202 dry, indoor use. See U bolts in MS, high tensile and SS for grades, finishes and matching nuts.

U Bolt Weight

The weight follows the rod length: two legs plus the half circle of the bend. On the DN50 size (M12 x 64 x 109) the bend runs on a 76 mm centreline diameter, 0.5 x 3.1416 x 76 = 119 mm of rod, and each leg below the bend is 109 − 32 − 12 = 65 mm, about 250 mm in all. At 7.85 g/cm³ that is about 220 g, close to the 222 g fasten.it lists. Work out any size with the U bolt weight calculator.

U Bolts from JMIKS Fasteners

JMIKS Fasteners supplies U bolts in SS 304, SS 316 and SS 202, mild steel 4.6 and 5.6, and high tensile 8.8 and 10.9, from M6 to M36 and 1/4″ to 1-1/4″ BSW, in lengths from 6 mm to 250 mm, with hex nuts and washers to match. Mild steel U bolts come hot dip galvanized or zinc plated for outdoor use. For a width outside the chart, send a drawing or a photo of the old bolt. See all our J, U and special type bolts.

U Bolt Size Chart FAQs

Which U bolt size do I need for a 2 inch pipe?

A 2 inch (DN50) steel pipe is 60.3 mm outside. The DIN 3570 size is an M12 U bolt with a 64 mm inside width, 76 mm leg centres, 109 mm height and 50 mm of thread.

Is a 50 NB pipe U bolt M10 or M12?

M12. A 50 NB (DN50) pipe is 60.3 mm outside, so the DIN 3570 width is 64 mm with an M12 rod. M10 U bolts stop at DN40 (48.3 mm pipe, 52 mm inside width).

Hot dip galvanized or stainless steel for outdoor pipe racks?

Hot dip galvanized mild steel suits most outdoor pipe racks. Near the sea, or where the plant handles chemicals or food, move to SS 304 or SS 316 with nuts and washers in the same grade.

How long should the thread on a U bolt be?

DIN 3570 gives 40 mm on the M10 sizes up to DN25, 50 mm from DN32 to DN80, 60 mm on M16 sizes and 70 mm on M20 and M24; fasteners.eu lists these as minimums. Ask for a longer thread if your plate is thicker than the 10 mm plate in the standard drawing.

Which U bolt fits a 4 inch pipe?

A 4 inch (DN100) pipe is 114.3 mm outside. DIN 3570 pairs it with an M16 U bolt: 120 mm inside width, 136 mm leg centres, 171 mm height and 60 mm of thread, ordered as M16 x 120 x 171.

Get a Quote for U Bolts

JMIKS Fasteners is a fastener wholesaler and supplier in Nava Odhav, Ahmedabad. Send the thread, inside width, height, material, finish and quantity on WhatsApp (+91 90333 11425) or through the enquiry form, or get our catalogue from the catalogue page. We reply within one working day.