A specifier pastes “ASTM A802 Level III” into a drawing for a structural bracket and ships the RFQ. Three foundries quote, and not one can tell whether Level III applies to the surface, the radiograph, the dimensional check, or all three. The clause is unenforceable.
Citing the wrong standard for the dimension being verified produces an RFQ a foundry cannot quote against. Picking an inspection level above what the part needs in service adds 15 to 30 percent to piece price without lowering field-failure rate.
The fix is sequential. Confirm sand casting fits the part, name the right standard for each dimension, match the level to criticality, then write language a foundry can defend.
Confirm Sand Casting Is the Right Process Before You Write Anything
Get the process wrong and the standard you cite is irrelevant. Sand casting is the correct ferrous default for parts above roughly 5 kg at 50 to 5,000 pieces per year.
Below that volume, investment-casting tooling is rarely amortizable. Above it, you are usually fighting investment on cost or die casting on alloy compatibility — die excludes steel and ductile iron entirely.
Forging wins on directional strength but loses on internal geometry. Any part with cores, undercuts, or hollow sections is off the forging table, which is why sand casting vs forging decides on geometry before strength.
Run this checklist before you write a single acceptance clause:
| Factor | Sand | Investment | Die | Forging |
|---|---|---|---|---|
| Material | Unlimited (incl. ferrous) | Unlimited (incl. ferrous) | Non-ferrous only | Limited by forgeability |
| Tolerance @ ≤100 mm | ±3.0 mm | ±0.5 mm | ±0.125 mm | ±0.5 to 1.0 mm |
| Surface (Ra) | 5–25 | 0.3–2 | 0.1–2 | 1–6 |
| Min order qty | 1 | 10 | 10,000+ | 50–500 |
| Internal geometry | Yes (cores) | Yes | Yes | No |
The order-of-magnitude tolerance gap between sand and investment is the fastest routing rule. A drawing demanding ±0.25 mm on a 50 mm feature will not hold as-cast on sand. Either the tolerance loosens, finish machining is budgeted, or the process changes.
I have seen procurement teams save 20 percent on piece price by switching to a process the part cannot tolerate, then lose 40 percent on rework when the first article fails.
Cite the Right ASTM Standard for Each Acceptance Dimension
Sand-casting acceptance is governed by different ASTM standards for different dimensions. Engineers default to A802 because it is the most-cited, but A802 covers visual surface only — citing it across radiographic, NDT, and dimensional acceptance produces an unenforceable clause.
Surface acceptance (visual)
ASTM A802 defines four levels (I through IV) across nine surface feature categories (A through J), against a 31-piece comparator set. Level I is the roughest qualifying finish, Level IV the smoothest a sand-cast surface can hold. In valve and pressure-piping work you may also see MSS SP-55 specified — same purpose, photographic-plate reference set instead of a comparator.
Internal acceptance (radiographic)
ASTM E446, E186, and E280 are reference radiographs governed by section thickness — citing the wrong one for your wall thickness produces a clause the foundry cannot quote.
| Standard | Section thickness |
|---|---|
| ASTM E446 | up to 2 in (50.8 mm) |
| ASTM E186 | 2 to 4½ in (50.8 to 114 mm) |
| ASTM E280 | 4½ to 12 in (114 to 305 mm) |
A 6-inch-wall valve body cited against E446 has no enforceable internal-acceptance language — E446 stops at 2 inches. Match the standard to the heaviest section you intend to inspect.
Surface discontinuities not visible to the eye
Liquid penetrant per ASTM E165 finds surface-breaking defects on any alloy. Magnetic particle per ASTM E709 is faster and more sensitive but only works on ferromagnetic alloys (carbon and low-alloy steels, ductile iron, gray iron — not 300-series stainless).
E125 supplies the reference photographs for ferrous MT acceptance grades. Route by alloy: PT for austenitic stainless, MT for carbon and ductile.
Dimensional and material
Dimensional acceptance is governed by ASME Y14.5 GD&T on the drawing, not by an ASTM standard. Material acceptance is the grade callout — A216 WCB, A352 LCC, A536 80-55-06, A48 Class 30 — each grade specifies chemistry and mechanical properties.
Match the Inspection Level to Part Criticality
Default Level III on every part is the most common over-specification trap. The Steel Founders Society of America puts it bluntly: severity levels are not graded to any basis of acceptability as to service performance — meaning you, not the standard, must map level to part need.
| Criticality | Service environment | Surface (A802) | Internal (E446/E186/E280) | Surface NDT |
|---|---|---|---|---|
| Tier 1: pressure-containing | Valves, pressure vessels, pump casings | Level II | Level 2 | 100% MT/PT |
| Tier 2: structural load-bearing | Brackets, housings, frames | Level II | Level 3 (critical sections) | Sample MT/PT |
| Tier 3: dimensional-fit | Gearboxes, fixtures, mating parts | Level III | not required | not required |
| Tier 4: decorative | Covers, trim, guards | Level IV | not required | not required |
Specifying Tier 1 acceptance on a Tier 3 bracket adds inspection cost without lowering field-failure rate — the part fails by yield, not by porosity. Specifying Tier 3 visual on a pressure-containing body is the failure mode that puts plants at risk.
Method-to-defect routing within each tier (when MT versus PT, when RT versus UT) follows test sensitivity, mapped in our NDT methods for sand castings breakdown.
Write Acceptance Language Your Foundry Can Quote Against
The pattern is: name the standard, the level, the dimension, and the rejection threshold. Specify what failure looks like, not what perfection looks like.
A Tier 2 structural bracket in carbon steel reads like this on the drawing:
> MATERIAL: ASTM A216 Grade WCB. Chemistry and mechanical per A216. > SURFACE ACCEPTANCE: As-cast per ASTM A802 Level III. Machined faces per drawing callouts. > INTERNAL ACCEPTANCE: Radiographic per ASTM E446, Severity Level 3, on critical sections marked on drawing. Sample: 1 per heat. > SURFACE NDT: Magnetic particle per ASTM E709, acceptance per ASTM E125 Type I/II Degree 1; 100% first article, 1 per 10 thereafter. > DIMENSIONAL: Per drawing GD&T (ASME Y14.5). Machining allowance 3/16 in. minimum; draft 1.5° unless specified. > REJECTION: Cracks, hot tears, and cold shuts at any level. Linear porosity exceeding the cited severity grade.
Every dimension names a separate standard, so the foundry knows which ruler measures which axis. Sample frequency is named, so the foundry knows the production cost to bid against. Rejection criteria are absolute (cracks at any level) and graded (porosity above Severity 3), so the inspector knows when to stop the line.
Limiting RT to critical sections marked on the drawing is the single change that recovers most of the over-specification cost.
Over-Specification Traps in Sand Casting Acceptance Criteria
The Steel Founders Society of America notes that designers often specify a quality level higher than the design requires, which serves no purpose except to increase cost. Reliance Foundry puts it directionally: the more testing and tighter the criteria, the more expensive the product, without necessarily increasing serviceability.
Industry rejection rates run 5 to 7 percent at well-run high-volume foundries. Setting acceptance tighter than that band buys you rework, not reliability.
Two traps account for most of the premium. Default Level III on parts that fail by yield rather than porosity adds inspection labor versus Level II without changing field life. Blanket 100 percent radiographic on parts where critical sections are 20 percent of casting volume buys nothing on the other 80 percent.
Next Steps
Treat acceptance criteria as a four-step sequence, not a single paste. Confirm the process fits the part, then cite a separate standard per dimension — A802 for surface, E446/E186/E280 for internal by section thickness, E709 or E165 for surface NDT, GD&T for dimensional.
Match level to criticality tier rather than defaulting to Level III, and write rejection language with sample frequency named.
When you factor in the total landed cost, the criteria block is the cheapest place to recover margin in the RFQ. Loosen the wrong dimension and the foundry ships parts that pass the spec but fail in service. Run the four steps before the next drawing leaves your desk.