STAINLESS STEEL FLAT WASHERS 3XD DIN 9021

Flat Washers 3xd DIN 9021 — 3xd is shorthand for a washer whose outside diameter runs to roughly three times its bore - a noticeably larger footprint than a standard DIN 125 or ISO 7089 washer for the same bolt size, and DIN 9021 is the formally dimensioned standard behind that description. That extra bearing area is specified wherever the clearance hole is oversized or slotted, or the clamped material is soft or thin enough that a standard washer would concentrate load into a small ring and risk crushing or pulling through - timber, thin sheet, or pre-existing holes that do not line up perfectly with the fastener. It performs a similar function to a penny washer, and the two names are sometimes used interchangeably in casual conversation, but where dimensional accuracy actually matters - matching a specific bolt diameter to a defined outside diameter and thickness on a drawing - DIN 9021 is the safer reference, since penny washer as a trade term does not carry a fixed specification behind it. It is a general engineering and construction washer rather than a structural one: where a connection is designed to structural steelwork practice, DIN 7989 remains the more directly applicable standard even though both washers are relatively large and thick. Material selection follows the usual pattern for large-diameter washers: mild steel with a protective zinc or similar plating for indoor, dry, or short-term applications, and A2 (304-equivalent) stainless as the standard step-up wherever the fixing is outdoors, exposed to weather, or subject to washdown. A4 (316-equivalent) earns its cost specifically in coastal, marine, or chemically exposed settings, where the combination of a large surface area and chloride exposure would otherwise accelerate pitting on a standard A2 washer. To specify correctly, match the bore to the fastener diameter and call up DIN 9021 explicitly wherever the application needs a defined large-diameter washer rather than an unspecified penny size.

FAQs
Is DIN 9021 interchangeable with ISO 7093-1?
Not automatically - both are large-diameter series but governed by separate standards with their own outside diameter and thickness tables, so dimensions should be checked before substituting.

Is DIN 9021 the same as a penny washer?
It serves a similar function and is sometimes referred to informally as a penny or mudguard washer, but DIN 9021 is a formally dimensioned standard, whereas penny washer is often used as a general trade term without a fixed specification.

Does DIN 9021's thickness change with size, or is it fixed?
Thickness scales with the bore across the standard's size range, so always check the specific table for the bolt diameter in question rather than assuming a single thickness across the whole series.