Material page for u-bolts in A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80). The sizes below are the ones we supply; there is no published dimensional standard for this article, so the table rather than a standard number is what to quote. Corrosion behaviour is superior, including marine and chloride environments and the service range is approx. -200 °C to +400 °C, subject to the property class and the joint.
Why Choose A4 Stainless Steel for U-Bolts
Specified for marine, coastal and chemical applications. For u-bolts, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For U-Bolts in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For U-Bolts, the alternative stainless grade is A2 (304). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
Using Stainless Fasteners in Aluminum
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of U-Bolts Available in A4 Stainless Steel
| Thread size | Pitch (mm) | Inside width A (mm) | Inside height / leg length B (mm) | Pipe size ref | Thread length (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M6 | 1.0 | 27 | 60 | 3/4 in | 25 | Industry standard | Round-bend U-bolt with 2 nuts |
| M8 | 1.25 | 34 | 75 | 1 in | 30 | Industry standard | Round-bend U-bolt with 2 nuts |
| M8 | 1.25 | 43 | 90 | 1-1/4 in | 30 | Industry standard | Round-bend U-bolt with 2 nuts |
| M10 | 1.5 | 49 | 110 | 1-1/2 in | 35 | Industry standard | Round-bend U-bolt with 2 nuts |
| M10 | 1.5 | 62 | 120 | 2 in | 35 | Industry standard | Round-bend U-bolt with 2 nuts |
| M12 | 1.75 | 77 | 140 | 2-1/2 in | 40 | Industry standard | Round-bend U-bolt with 2 nuts |
| M12 | 1.75 | 90 | 160 | 3 in | 40 | Industry standard | Round-bend U-bolt with 2 nuts |
| M16 | 2.0 | 115 | 200 | 4 in | 50 | Industry standard | Round-bend U-bolt with 2 nuts |
| M16 | 2.0 | 140 | 220 | 5 in | 50 | Industry standard | Round-bend U-bolt with 2 nuts |
| M20 | 2.5 | 168 | 260 | 6 in | 60 | Industry standard | Round-bend U-bolt with 2 nuts |
Dimensions are independent of the material: every size above is available in A4 Stainless Steel.
Custom manufacturing · Made to drawing
Need this bolt in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Dimensions, material, finish and form are specified from the drawing — a bolt outside the standard range is a variation on existing tooling rather than a new design. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
