A quality engineer at a stamping operation ordered cold-rolled steel sheet to ASTM A1008 CS Type B. When the MTCs arrived, the general requirements reference on the cert showed ASTM A6. She flagged it during her MTC review. The receiving supervisor said the auditor hadn't mentioned it on the last audit. She filed a supplier corrective action anyway.
Three months later, during a Tier 1 automotive customer audit, the auditor pulled that cert as part of a traceability sample. He noted the A6 reference and asked how the company verified dimensional tolerance compliance for cold-rolled sheet. The quality engineer pulled the A1008 cert. She had the corrective action on file. The auditor gave her a minor finding and moved on.
The receiving supervisor's instinct — the auditor didn't flag it last time, so it's probably fine — is how small documentation errors become audit findings.
The Role of General Requirements Standards
ASTM product specifications don't stand alone. They invoke a "general requirements" standard that governs dimensional tolerances, permissible variations, testing frequency, marking requirements, and test methods that apply to the entire product category.
ASTM A6 covers general requirements for rolled structural steel bars, plates, shapes, and sheet piling. When you order structural plate (A36, A572, A514), structural shapes (A992, A500), or structural bar, the product spec invokes A6. An MTC for structural plate that correctly shows "ASTM A36 / General Requirements per ASTM A6" is properly documented.
ASTM A568 covers general requirements for steel, carbon, structural, and high-strength, low-alloy hot-rolled sheet and cold-rolled sheet. When you order hot-rolled sheet (A1011), cold-rolled sheet (A1008), or high-strength sheet (A606, A607), the product spec invokes A568. An MTC for cold-rolled sheet that shows "ASTM A1008 / General Requirements per ASTM A568" is correct.
These two standards govern different dimensional tolerance tables, different thickness permissible variation tables, different testing frequencies, and different marking requirements. They are not interchangeable. Using A6 on a sheet cert is not a clerical error in the sense of a typo — it's a reference to the wrong governing standard for the product being certified.
What A6 and A568 Actually Govern
ASTM A6 specifies dimensional tolerances for structural products — plate thickness tolerances by width and thickness range, flatness tolerances for plate, length and width tolerances, and camber requirements for structural shapes. It also specifies test frequency requirements for structural product (typically one test per heat for standard product) and the permissible variations that define acceptance criteria for dimensional inspection.
ASTM A568 specifies dimensional tolerances for sheet products — thickness tolerances by width and weight class, flatness tolerances appropriate for sheet coil and cut sheet, coil width tolerances, and telescoping limits for coil product. The tolerance tables are different from A6 because sheet is produced on different equipment to different commercial standards than plate or structural shapes.
If you're stamping parts from cold-rolled sheet and your dimensional acceptance criteria are based on A568 tolerances, a cert that invokes A6 doesn't document compliance to the tolerances you're actually holding material to. The cert references a standard with different tolerance tables. If a part fails and you need to demonstrate the incoming material met spec, your documentation has a gap.
Why Auditors Find This
Third-party auditors reviewing MTCs look for internal consistency. The product spec should invoke a general requirements standard appropriate for the product form. When an auditor sees A1008 CS Type B on a cert and A6 cited as the general requirements standard, the mismatch is visible to anyone who knows what A6 and A568 cover.
The audit finding isn't typically "your material is nonconforming." It's "your documentation doesn't demonstrate compliance to the standard you ordered to." That distinction matters in automotive, aerospace, and pressure-equipment supply chains where document-based compliance demonstration is an explicit requirement.
In automotive supply chains (IATF 16949 environments), a documentation gap on incoming material certification is a major finding under the control of externally provided processes clause. Suppliers are expected to verify that incoming certs are accurate, complete, and reference the correct standards — not just that the chemistry and mechanical values look reasonable.
Building the Check Into Your Review Process
The A6/A568 check is a two-field comparison: product form from the PO (structural vs. sheet/strip) and general requirements reference on the MTC. It takes five seconds. The challenge is making sure someone does it on every cert rather than only when something else looks wrong.
An automated MTC validation system that is configured with a lookup table of "product spec → expected general requirements standard" catches this mismatch on every cert without requiring the reviewer to know the A6/A568 distinction from memory. The system flags the mismatch, the reviewer resolves it with the supplier, and the file documents the resolution.
For operations that review MTCs manually, adding "general requirements standard appropriate for product form" to the MTC checklist ensures the check happens consistently rather than only when someone happens to notice.