2026-09-17 Procurement & Inventory

Fastener RFQ Checklist: How to Specify Bolts & Nuts for Accurate Quotes

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Introduction: Why Quotes Go Wrong

A quote can be off in three ways: the price is too high because the factory added a generous safety margin for unknowns; the price is too low because the factory assumed the cheapest standard interpretation and you pay for the difference later in rework; or the delivery time is padded because nobody knew which coating or test the order actually required.

None of these is a dishonest supplier. They are all failures of specification. In the years we have handled export fastener orders across different industrial markets — from small OEM batches to project-driven quantities — the orders that went smoothly were the ones where the buyer sent a complete specification in the first message. This checklist is that specification, block by block.

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Block 1: Dimensions — Metric or Imperial, Say Which

The minimum is diameter, pitch, and length — and the thread system it belongs to. State clearly whether your project uses metric (DIN/ISO) or imperial (inch-based) threads:

Metric (DIN/ISO): specify nominal diameter, pitch, and length in mm, plus the thread tolerance class where it matters, e.g., M16x1.5 x 80 mm, thread fit 6g (bolt) / 6H (nut).
Imperial (ASTM/ASME): specify nominal diameter in inches, threads per inch (TPI), and length in inches, plus the thread fit class, e.g., 3/4"-10 UNC x 3", Class 2A fit.

The three most common mistakes in this block are:

Pitch missing for fine threads. M16 and M16x1.5 are different parts. If the thread is fine, write the pitch.
Length definition. Bolt length is measured from under the head to the tip for hex bolts (DIN 933/EN ISO 4017), but some head styles measure overall length. Write "length measured from under head" or "overall length" when it matters.
Mixing thread systems. A metric bolt cannot be substituted into an imperial assembly. If the project standard is metric, keep the whole specification metric; if it is ASTM/ASME, use inch dimensions and TPI. Mixing the two in one RFQ is the fastest way to get a wrong quote.

Include a drawing whenever the part is not a catalog item. A simple dimensioned sketch removes more ambiguity than ten paragraphs of description.

Block 2: Material and Property Class — Keep the Two Systems Apart

Two different naming systems are in use, and they must not be mixed in one specification:

ISO system (metric): property class. For carbon and alloy steel fasteners, the property class (8.8, 10.9, 12.9 per ISO 898-1 / EN ISO 898-1) defines the mechanical properties. Do not write "high strength" or "good quality" — those are not specifications.
ASTM system (imperial): steel grade. ASTM designations such as A193 Grade B7 or A320 Grade L7 name a material grade with defined properties. If your project references an ASTM grade, give the full designation, not "B7 equivalent."

What to state:

Property class or material grade, e.g., 8.8 or 10.9 (ISO), or A193 B7 / B7M (ASTM), plus the nut class (8 or 10) if the nut matters.
Material grade where the project requires it, e.g., 35CrMo, 40Cr, 42CrMo4, or 316 stainless (A4-80 per ISO 3506).
Any chemical composition limits the project specifies, and whether a material certificate to EN 10204 3.1 is required with the quote or only with the delivery.

If you only need "whatever meets 10.9," say so. If the project owner's spec calls out a specific material, say the material name and the standard it comes from.

Block 3: Coating and Surface Finish

The coating block is where most RFQ mismatches happen, because coating choice changes both the price and the lead time significantly.

Type of coating: hot-dip galvanized (HDG for fasteners per ISO 10684, or ISO 1461 where the project calls it for structural components), electroplated zinc (with or without passivation), Dacromet / zinc-flake (ISO 10683), Zn-Al-Mg, plain (no coating), or stainless steel as-supplied.
Coating thickness in µm where it is a requirement, e.g., "HDG 45–80 µm average per the applicable standard" or "zinc-flake 8–12 µm." Where the applicable standard defines thickness by size (as ISO 10684 does), name the standard instead of fixing a single number.
Thread allowance after coating. HDG or thick coatings can affect thread fit. If the assembled fit is critical, state that thread fit must be verified with gauges after coating.
Hydrogen embrittlement concern for hardened parts (10.9 and above) with electroplating. If the application is safety-critical, state the requirement explicitly so the factory controls the process (e.g., baking per ISO 4042 or non-electrolytic zinc-flake).

Block 4: Standard and Designation

Name the standard you want the part to conform to: DIN 933, EN ISO 4017, DIN 931 / EN ISO 4014, GB/T 5782, ASTM F3125 (including Grade A325 and A490-type structural bolts), EN 14399, and so on. The standard determines head dimensions, thread lengths, and tolerance classes — and whether the system is metric or imperial.

If the project uses a standard that is not common in the manufacturer's home market, write the full designation and, where helpful, the closest equivalent. A supplier that knows both GB and DIN/ISO systems can convert without losing the requirement.

Block 5: Tolerances and Special Features

Anything that is not a standard catalog part needs explicit tolerances:

Special head geometry (flange, countersunk, socket, custom), with dimensions.
Drilled holes, slots, or cross-holes, with position and diameter tolerances.
Thread length or grip length that differs from the standard.
Dimensional tolerance in mm, e.g., "head height ±0.1 mm," "under-head radius R0.6 max."

If you do not state a tolerance, the factory will use the standard product tolerance — which may be wider than your application needs.

Block 6: Mechanical Tests Required

Beyond property class, state which tests the lot must show evidence for:

Hardness (HRC/HBW) per batch
Tensile / proof load test
Wedge loading (for bolts)
Charpy impact (for low-temperature service)
Preload suitability / torque coefficient (for structural bolting, e.g., EN 14399-2)

Also state whether the tests are standard production tests (included in the price) or witnessed by a third party (adds cost and time).

Block 7: Documents and Certification

The documentation requirement changes the quote. State clearly:

EN 10204 3.1 MTC (material test certificate) — the common export standard, included or at small cost.
EN 10204 3.2 (third-party certified) — adds inspection cost and time.
Heat number traceability per batch, if required by the project QA plan.
Third-party inspection (SGS, BV, TÜV or client's inspector) — state who pays and at what stage.

Block 8: Packaging and Delivery

Quantity, in pieces or tons, and whether a single lot or phased delivery.
Packaging: cartons, pallets, steel drums; whether barcoded pallet labels are required.
Rust protection for long sea freight: VCI paper, rust-preventive oil, or coating as the only protection.
Port of delivery and incoterm (FOB, CIF, DAP), target delivery date, and whether partial shipments are acceptable.

Block 9: The Reference Part or Drawing

If the order is a repeat or an existing product, give the previous part number or a photo. A photo of the actual part (with a scale) plus a dimension table is often enough for the factory to quote correctly.

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A Fill-in RFQ Template

Copy this block into your next inquiry and fill it:

Product: hex bolt / hex nut / stud bolt / custom part
Qty: ______ pcs (or ______ tons)
Standard: DIN ___ / ISO ___ / GB ___ / ASTM ___ / other
Dimensions: Size ___ (M or inch) x Pitch/TPI ___ x Length ___ (mm or inch) (length measured: under head / overall)
Property class: 8.8 / 10.9 / 12.9 / A2-70 / A4-80 / other
Material: ____________ (if specified)
Coating: none / HDG ___ µm / zinc / zinc-flake ___ µm / Zn-Al-Mg / other
Thread tolerance: 6g / 6H / other
Special features: ______________________________________
Tolerance notes: ______________________________________
Tests required: hardness / tensile / wedge / impact / preload suitability per EN 14399-2 (torque coefficient where applicable)
Documents: EN 10204 3.1 / 3.2 / heat traceability / third-party inspection
Packaging: cartons / pallets / drums; VCI: yes/no
Delivery: incoterm _____, port _____, target date _________

Send this to the factory together with your drawing or photo, and the quote you get back will be close to the final order — in price, in lead time, and in documents. If your specification is incomplete, a good supplier will identify the missing parameters before quoting rather than after production starts — ask for that confirmation explicitly.

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Common Specification Mistakes That Cost Time

Writing "high strength bolts" without a property class.
Forgetting pitch for fine threads.
Asking for HDG without a thickness range — you get "galvanized" and it passes or fails depending on the inspector's day.
Requiring a 3.2 certificate after the order was quoted without it, then paying the difference.
Not mentioning hydrogen embrittlement control for 10.9 electroplated parts in a safety application.

Each of these is a one-line fix in the RFQ and a multi-week problem if left until after production starts.

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FAQ

Q1: How much detail is too much for a first RFQ? More is better up to the point of clarity. A complete block-by-block specification is about 10 lines; a drawing adds the rest. Do not send a 40-page QA manual for a first quote — send the specification and ask which documents the factory needs for its own process.

Q2: Can I get a quote without specifying the standard? Yes, but the quote will carry assumptions. The factory will pick the closest standard to the dimensions you gave, and that choice may not match your project's acceptance criteria. Specify the standard whenever the project references one.

Q3: Do I need to specify coating thickness for standard orders? If the application is outdoor or industrial, yes. Without a thickness range, "HDG" can legitimately mean anything from 40 to 85 µm depending on the process and the factory.

Q4: What does a 3.1 MTC actually prove? It states that the manufacturer declares the delivered lot meets the specified material and test requirements, based on the factory's own production testing and traceability. It is the standard export document for structural and industrial fasteners.

Q5: Will a complete specification make the quote more expensive? No. It removes the safety margins suppliers add for unknowns. A complete specification usually returns a more competitive and more reliable quote than a vague one.

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Request a quote: Send your specification and drawing to our engineering desk — we respond within one working day with pricing, lead time, and a confirmation of exactly which test and document package is included. If the spec has gaps, we will tell you before quoting, not after.