DN25 U-Bolt Dimensions Chart (for 33.7 mm Pipe)

{dn} U-Bolt Dimensions (unit mm)

Form: round bar bent into a U with threads cut or rolled on both leg ends, closed by nuts and washers to clamp pipe or section. Round bend (semicircular) and square bend (right-angle) are distinct forms agreed by drawing; this chart covers the round bend basis.

Thread pairing source tags: "Catalog pairing" means the value was extracted size by size from the spec_json of U-bolt SKUs in the product catalog (same source as the product pages; the extraction script ops/tools/gen-ubolt-dims.py can be re-run to verify). "Assumed" would mean the catalog has no SKU covering that pipe-OD band and a conventional pairing was assumed and flagged here. All 11 bands in this chart are catalog pairings; none is assumed.

Pipe OD Reverse Lookup: Which U-Bolt Fits (all 11 sizes)

Sizing entry point: measure the actual pipe outside diameter, find that band in the left column, and the same row gives the inside width, leg length, overall height and matching thread for that pipe size; click the DN number to open that size. Pipe ODs follow the GB/T 1047 metric series. If the measured OD falls between two bands, or the pipe is inch (NPS), size to the next band up and confirm with the supplier.

"Rod diameters available" lists every round bar diameter the catalog offers for that pipe-OD band; the default pairing is the lightest of them (tagged on each size page), and one step up suits heavy or vibrating duty. Bend type, thread length and the number of matching nuts and washers are confirmed by drawing or at inquiry.

A U-bolt's unit weight moves with rod diameter and developed length together: developed length = 2 x leg length + bend centreline length (a semicircle of radius (inside width + rod diameter)/2), so the bend grows with the rod too and each step up in diameter adds weight faster than the square of the diameter alone.

Unit weight = developed length x pi/4 x d^2 x 7.85 g/cm3 for carbon steel, rounded to avoid false precision (whole g below 100 g, 10 g steps below 1,000 g, 100 g steps above). Matching nuts and washers are counted separately; see the related charts at the foot of the page.

Material Density Conversion

Table values are for carbon steel (7.85 g/cm3); other materials convert by density ratio: weight x factor (geometry unchanged).

Calculation Basis and Assumptions Disclosed

Dimensions come from fastenerCalc: inside width, leg length and overall height are mapped from UB_PIPES (DIN 3570 series geometry, same source as the product catalog SKUs); the matching thread size comes from UB_THREAD (extracted size by size from the live prd_sku.spec_json, see the source tag in the table above); pitches follow the GB/T 196 metric coarse table. Unit weights are all computed from geometry: developed length = 2 x leg length + bend centreline length, the bend taken as a semicircle on the centreline (radius = (inside width + rod diameter)/2), rod at nominal full diameter, 7.85 g/cm3 for carbon steel, base metal only, coating excluded. This developed-length convention matches the catalog spec_json developedLengthMm for every size.

Rolled-thread allowance disclosed: the main table is computed at nominal full diameter (the same basis as the catalog unit_weight_g, so it reconciles row by row). The threaded portions of both legs are roll formed and lose a little material; applying the 0.97 rolled-thread allowance (THREAD_ROLL_ALLOWANCE) puts this size at roughly {rolled} g/pc, about {factor}% lower. Either basis can be used for batch costing; the main table stays unadjusted so it matches the catalog.

Boundary: unit weights are theoretical geometry estimates for quotation, freight and packing budgets; actual weight varies with bend radius, thread accuracy and coating (hot-dip galvanizing roughly +4.5%), and trade settlement is against actual measurement. Inside width, leg length and overall height are catalog-modelled dimensions; square bends, extended legs, inch pipe (NPS) and special thread forms are made to drawing, and this chart is not an acceptance basis.