Attribute Schema Library
Attribute schemafastener distribution

Washers Attributes for Fastener Distributors

A washer spreads clamp load, spans an oversized or slotted hole, protects a finish, or (Belleville and wave types) acts as a spring holding preload through thermal cycling. Distributors stock them across a dozen types, two measurement systems, and most combinations of material and plating. Buyers are MRO storerooms, steel fabricators and erectors, OEM production, and contractors pulling to a submittal.

Nominal size is not a dimension. A "1/2 in" washer is a use-with value; the actual ID is 0.531 in SAE or 0.562 in USS, two different parts sharing one description. The same washer is called fender, penny, mudguard, repair, or DIN 9021 depending on whose file you opened. Hardness rides on the standard number rather than the part record, so DIN 125A at 140 HV and ISO 7089 at 300 HV read as interchangeable on a dimension table and are not.

The governing spec sits in a supplier PDF dimension table keyed to a standard, never on the line item. Type x size x material x finish x standard yields thousands of SKUs from a few reused description strings.

Core

Every SKU needs these. Without them the record is not a product, it is a row.

Washer Type
enum
Structural Flat Washer (F436 Type 1)

Determines what the part does. A flat washer, a split lock, and a Belleville are not substitutes. Buyers filter here first.

For Screw Size (Nominal)
enum
1/2 in

The use-with value every buyer starts from. It pairs the washer to the bolt on the print, and it is never the same number as the ID.

Inside Diameter
number · in or mm
0.531 in (1/2 in SAE)

The actual hole. Buyers clearing a shoulder, weld bead, fillet, or oversized hole filter on ID, not on nominal size.

Outside Diameter
number · in or mm
1.375 in (1/2 in USS)

Sets bearing area and whether the washer spans the hole or fouls an adjacent fastener, fillet, or beam flange.

Thickness
range · in or mm
0.074-0.121 in (1/2 in SAE)

Published as a min/max band on most datasheets. Buyers stacking to a grip length or fitting a countersink need both limits.

Material / Grade
enum
Stainless Steel, 18-8 (A2)

Drives corrosion behavior, galvanic pairing with the bolt and the joint, and price. 18-8 and 316 are not interchangeable in chloride.

Finish / Coating
enum
Zinc Plated, ASTM B633 SC1 Type III

Corrosion life and RoHS status both live here. Hot-dip galvanizing also changes fit, since the coating adds thickness inside the hole.

Manufacturer Part Number
identifier
M51420.120.0001

The join key for cross-reference, supplier price files, and customer punchout. Without it, every substitution is a manual lookup.

GTIN / UPC
identifier
GTIN-14 on the box, GTIN-12 on the each

Required for marketplace listing and scan-based vending. Washers sell by box, so the pack-level GTIN is not the each-level GTIN.

Package Quantity / UOM
number · pieces per pack
100 per box (sold per box)

Washers are quoted per 100 or per 1,000 and picked as each. Ambiguity here produces order-quantity errors and margin leaks.

Differentiating

What buyers actually compare on. This is where catalogs win or lose the filter.

Dimensional Standard
enum
ASME B18.22.1 Type A Wide

The single field that pins ID, OD, and thickness. A buyer holding a print filters on the callout, not on measurements.

Series / Pattern
enum
USS (1/2 in: 0.562 ID x 1.375 OD)

USS and SAE washers for the same bolt size differ in ID, OD, and thickness. Without this field both collapse into one facet value.

Hardness Class
enum · HV or HRC
300 HV

Decides whether the washer holds preload or dishes. 200 HV suits bolts to 8.8, 300 HV to 10.9; F436 through-hardened is 38-45 HRC.

Spring Load at Flat
number · lbf or N
1,320 lbf at 0.023 in deflection

A Belleville or wave washer is a spring. Without load at flat and the deflection it occurs at, the stack cannot be sized, only guessed.

Edge Condition
enum
Chamfered (ISO 7090)

ISO 7090 is chamfered, ISO 7089 is not. Matters under a bolt head radius or a fillet where a square edge will not seat flat.

Compliance & identifiers

Standards, regulatory data, and the identifiers channels reject you for missing.

Country of Origin
identifier
United States

Drives duty, Buy America eligibility on public work, and DFARS questions. Asked on most construction and government RFQs.

RoHS / REACH Status
enum
RoHS compliant (trivalent Cr(III) passivate)

Turns on plating chemistry, not colour. Hexavalent chromate yellow zinc fails RoHS; trivalent passivate passes.

Certification Available
enum
EN 10204 3.1 available; F436 CoC on request

Submittals and QA receiving ask for mill certs. Whether you can produce EN 10204 3.1 or a CoC decides the line, not the price.

The fields that aren't in the schema at all

What most washers catalogs are missing.

The table above is the schema most catalogs already have. These are the attributes that usually aren't in it — each one surfaced by a signal from the live market rather than by an audit of what's already there. This is what Anglera's Schema Foundry does on a real catalog, in this category.

Competitor signal
+ Hardness Class (HV / HRC)

McMaster and the metric fastener specialists expose 140 HV / 200 HV / 300 HV as a selectable spec. Most distributor washer records carry 'Steel, Zinc Plated' and no hardness field at all.

Pair a 140 HV DIN 125A washer with a 10.9 bolt and it dishes under the head, and the joint loses preload. A wrong-part return at best, a field failure at worst.

Search signal
+ Series / Pattern (USS vs SAE)

Buyers search 'SAE flat washer 1/2' and 'USS washer 1/2' as separate queries. Catalogs that describe both as '1/2 in flat washer, zinc' return the same undifferentiated set to both.

1/2 in USS is 1.375 in OD; SAE is 1.062 in. Same description, different part. The picker ships whichever is in the bin and the bearing area is wrong.

Supplier signal
+ Thickness min/max band

Manufacturer dimension tables publish thickness as a band (1/2 in SAE: 0.074-0.121 in). Catalog records collapse it to one nominal figure, or drop thickness entirely.

Buyers stacking washers to a grip length or fitting a countersink need both limits. A single nominal number cannot answer it, so the RFQ goes elsewhere.

Supplier signal
+ Spring load at flat (Belleville / wave)

Disc spring makers publish load at flat and deflection per DIN 2093 series A/B/C. Distributor Belleville listings typically carry OD, ID, and overall height, and stop there.

A Belleville is a spring sold as a washer. With no load figure the buyer cannot size the stack, and calls whoever published the curve instead.

Supplier signal
+ Chromate chemistry: Cr(VI) vs Cr(III)

'Yellow zinc' covers both legacy hexavalent dichromate and RoHS-compliant trivalent passivate. Catalogs print the colour; the RoHS declaration turns on the chemistry.

EU-bound and RoHS-scoped orders reject on Cr(VI). The line is refused at receiving, or you cannot produce the declaration and lose the account.

How Schema Foundry finds these

Messy in, governed out.

The same value, spelled every way fastener distribution suppliers spell it. A filter only works once they agree.

Material / Grade
18-8SS304A2-7018/8 StainlessT30418-8 SS
Stainless Steel, 18-8 (A2)

18-8 is a family, not a grade. A2 is the metric callout, 304 the alloy. 316/A4 must never fold into the same bucket.

Finish / Coating
Zinc YellowYZPYellow DichromateGold ZincZinc/Yellow ChromateTrivalent Yellow
Zinc Plated, Yellow Chromate, Cr(III)

The colour name says nothing about hexavalent vs trivalent. RoHS turns on the chemistry, so the governed value has to carry it.

For Screw Size (Nominal)
1/20.5001/2 inM12#12.5 inch
1/2 in

Fraction, decimal, metric, and gauge notations land in one column. #12 is a screw gauge, not 12 mm, and a text sort scrambles the facet.

Washer Type
FenderPennyMudguardRepairDIN 9021Large OD
Fender Washer

Penny and mudguard are UK usage, fender and repair US, DIN 9021 the spec. One part, five names, and no facet hits on four of them.

What buyers ask

Every one of these should be answerable from the attributes above. If it isn't, that's a gap.

  • Is this USS or SAE? The print calls out SAE and the two aren't the same OD.
  • What's the actual ID? I need it to clear a shoulder, not just fit a 1/2 bolt.
  • Will this hold up under a 10.9 bolt, or is it going to dish?
  • Is the yellow zinc trivalent or hexavalent? Part of this order ships to the EU.
  • Is that price per each or per hundred, and how many come in a box?
  • What's the load at flat on the 3/8 Belleville, and at what deflection?
  • Can you send a 3.1 mill cert with it? This is going into a submittal.
  • Is it domestic? The job is Buy America and I need origin on the packing slip.

What channels require

The same SKU, different mandatory fields per destination.

Distributor's own site (faceted search)
Washer TypeFor Screw Size (Nominal)Inside DiameterOutside DiameterThicknessMaterial / Grade
Amazon Business
GTIN / UPC (or exemption)Manufacturer Part NumberPackage Quantity / UOMMaterial / GradeFor Screw Size (Nominal)Country of Origin
Zoro / Grainger supplier catalog feed
Manufacturer Part NumberGTIN / UPCFor Screw Size (Nominal)Outside DiameterThicknessFinish / Coating
Construction submittal / RFQ package
Dimensional StandardHardness ClassFinish / CoatingCountry of OriginCertification Available

Washers data, in practice

Is a hardened washer the same as a structural washer?

Close, but they are different fields. ASTM F844 covers unhardened plain washers for general use: no hardness requirement, dimensioned to the USS or SAE pattern. ASTM F436 covers hardened washers for nominal thread diameters of 1/2 through 4 in, through-hardened to 38-45 HRC, relaxed to 26-45 HRC when hot-dip galvanized, and it is what pairs with F3125 Grade A325 and A490 structural bolts. F436 also defines beveled washers (1:6 taper for American beams and channels), clipped washers, and extra-thick washers at 5/16 in nominal. Keep Dimensional Standard and Hardness Class as separate attributes: the standard gives the pattern, the hardness tells you whether the washer holds preload.

DIN 125 or ISO 7089 - can I substitute one for the other?

Dimensionally, across the common metric range, yes. Both are product grade A plain washers and ID, OD, and thickness track closely. Mechanically, not automatically. DIN 125A is commonly stocked at 140 HV. ISO 7089 is specified in 200 HV and 300 HV classes: 200 HV suits hexagon bolts and screws in property classes up to and including 8.8 and nuts up to class 8; 300 HV suits up to 10.9 and nuts up to class 10. Swap a 140 HV washer under a 10.9 bolt and it can dish. This is exactly why Hardness Class has to be its own attribute rather than something a buyer is expected to infer from the standard number.

Why carry Inside Diameter if the record already has For Screw Size?

Because they are different numbers. For Screw Size is a nominal use-with value; ID is the hole. A 1/2 in SAE washer has a 0.531 in ID, a 1/2 in USS washer 0.562 in, and both are labelled '1/2 in'. Buyers clearing a shoulder, a weld bead, a fillet, or an oversized or slotted hole filter on ID. The gap is widest on fender washers, where the whole point is a small hole and a large OD (DIN 9021 / ISO 7093 run roughly 3x nominal thread), and on hot-dip galvanized parts, where the coating adds thickness inside the hole. Publishing only nominal collapses distinct SKUs into one facet value and makes the size filter useless for the people who need it most.

Do washers fall under the Fastener Quality Act?

Mostly not. The FQA definition at 15 U.S.C. 5402 covers metallic screws, nuts, bolts, and studs having internal or external threads at 6 mm / 1/4 in nominal diameter and larger. Plain washers, lock washers, and Bellevilles sit outside it. The named exception is the load-indicating washer: direct tension indicators to ASTM F959, used with F3125 Grade A325 and A490 structural bolts. Those are in scope when through-hardened, or represented as meeting a consensus standard calling for through-hardening, and grade-identification marked. If you stock F959 DTIs they carry traceability and insignia obligations the rest of your washer catalog does not, and that belongs in a field.

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