A purchase request for ‘stainless bolts’ leaves several questions open. The alloy, fastener property class, thread, surface condition and accompanying documents all affect what the supplier must quote. Comparing 304 and 316 is useful, but the grade name alone does not describe a complete fastener.
Start with the environment, then confirm the material
316 is a molybdenum-bearing austenitic stainless steel. Molybdenum improves resistance to some forms of localized corrosion compared with conventional 304, but it does not make 316 immune to corrosion. Outokumpu’s guidance also explains why laboratory corrosion data must be assessed against the actual service medium and conditions. Material reference · Corrosion-data limitations.
Tell the responsible materials engineer whether the connection is indoors, outdoors, exposed to salt spray, immersed, periodically washed, or in contact with process chemicals. Temperature, cleaning agents, trapped moisture and contact with other materials deserve attention. A description such as ‘marine grade’ does not replace that review.
Keep alloy designation and fastener strength requirements separate
A material designation identifies an alloy requirement. A fastener specification also needs the applicable property class and product standard. ISO 3506-1 covers mechanical and physical properties of specified stainless steel bolts, screws and studs; its public scope does not establish torque/clamp-force, fatigue or shear requirements. ISO scope.
If a drawing specifies 316L, do not silently change the order to 316. Likewise, a shorthand request for A2 or A4 should be checked against the required standard and property class; it should not be treated as proof that a particular mill alloy or finished fastener meets every project requirement. Ask for a clearly identified proposed specification and resolve any substitution before ordering.
Build an RFQ that suppliers can compare
| Information | What to provide |
|---|---|
| Material and strength | Alloy designation, governing specification and edition, required property class or condition. |
| Geometry | Product standard or drawing, diameter, pitch, length, head style and full or partial thread. |
| Assembly | Matching nut and washer requirements, mating materials and the approved assembly procedure. |
| Surface and documents | Required finish, identification, inspection scope, certificate type and traceability. |
Review the whole fastening set
Do not compare a bolt-only quotation with a complete bolt, nut and washer set. List the number of each component per assembly and require the supplier to identify any proposed deviation. For a replacement order, include the original drawing revision rather than relying only on a photograph or the markings on one used component.
Ask whether the quoted finish is the final supplied condition and whether any proposed lubricant or coating is compatible with the project’s assembly requirements. Do not carry a torque value from one surface condition to another without checking the approved procedure.
Check the quotation before release
For each line, compare the offered material, strength requirement, dimensions, finish, quantity and documentation against the RFQ. Separate a confirmed requirement from an option still awaiting approval. If an inspection certificate is required, agree its scope before purchase; the word ‘certificate’ alone is not a complete document instruction.
WISINE’s stainless steel range, 316 / 316L material page and bolt range provide starting points for product discussions. Send the approved specification and quantity for an order-specific review.
Discuss Your Specification with WISINE
Send the product type, material requirement, dimensions, quantity and current drawing or specification for review.
Sources and Further Reading
This article supports procurement preparation. Use the approved drawing, applicable standard edition and project requirements for design and acceptance decisions.
