Ductile Iron Square Flat Washer — Sand Cast Per ASTM A536

By Nico Yin · Qingdao Zhaoyuqi Machinery Co., Ltd.

Overview

A square flat washer is a square-shaped load-distribution plate with a central hole, cast in ductile iron to sit under the head or nut of a square-head bolt or lag screw. Compared with a round washer of the same nominal size, the square profile places more material in the corners, spreading clamp load across soft or irregular bearing surfaces such as wood crossarms, cast pole-line hardware, and unfinished structural steel. Typical ratings are defined by the mating bolt size rather than the washer itself.

In our production program, the square flat washer serves two core purposes. First, it is supplied as the companion component to square head plugs and square-head fasteners used across waterworks, fire protection, and power fitting assemblies. Second, it is used under pipe support hardware — saddle supports, brackets, and U-bolt assemblies — where a wide bearing surface prevents bolt heads from pulling into drilled or slotted holes. Because the washer is sand cast rather than punched from sheet, wall thickness and corner geometry can be tailored to the assembly without the tooling cost of stamping dies, and quantities from pilot lots to full production runs are practical.

Specifications

The ductile iron matrix gives the washer measurable elongation, so it deforms rather than cracks when a square head bolt is over-torqued on an uneven surface — a common failure mode for gray iron or low-carbon stamped alternatives. Both imperial bolt series and metric hole patterns are routinely produced from customer sketches or samples.

Installation & Application

Installation is straightforward: the washer sits between the rotating square head (or nut) and the bearing surface, with the cast face against the structure and the machined or as-cast face under the bolt. On pole-line hardware such as clevis eyes and yoke plates, square washers back up through-holes in wood poles and crossarms. On pipe support assemblies, they distribute the clamping force of U-bolts and hold-down bolts across bracket feet. Typical applications include:

• Backing plates for square head plugs in tapped cast fittings

• Bearing plates under lag screws on wood crossarms and pole structures

• Load-spreading washers under pipe saddle and bracket anchor bolts

• Shim and spacer duties in heavy mechanical assemblies

Customization & Sampling

Washers are cast to drawing: square width, hole diameter, thickness, corner radii, and chamfers are all adjustable. We can consolidate several washer sizes into one pattern family with machined inner diameters to reduce your inventory. Samples are typically available for dimensional approval before mass production. Furnace and tensile records are maintained for every pouring batch.

Quality Inspection & Packaging

Each lot receives dimensional inspection against the customer drawing, material verification against the heats of ASTM A536 iron poured, and coating thickness checks for hot-dip galvanized lots per ASTM A123. Parts are deburred, sorted by size, and packed in cartons or bulk bags on export pallets; mixed-size pallets are available for distributor programs.

FAQ

Why a square washer instead of a round washer?

The square shape provides a larger bearing area at the corners, which matters on wood poles, crossarms, and soft base materials where a round washer can dig in. It also self-locates against square-head hardware.

Can you match an existing washer sample?

Yes. Send the sample or a sketch with outer width, hole size, and thickness; we will quote from the pattern or produce first-article castings for approval.

What coating survives outdoor installation?

Hot-dip galvanizing per ASTM A123 is the standard choice for pole-line and waterworks hardware; epoxy is offered where additional corrosion protection or color matching is required.

Related Products

• Square Head Plugs — companion square-head closures for tapped fittings

• Bar Plugs (Cored) — cored plugs for pipe bell ends and test capping

• Clevis Eye — pole-line hardware often assembled with square washers

• Support Bracket — cast brackets using washer-backed anchor bolts

• Rod Coupling Straight — threaded rod connections in support assemblies

Get a Quote

Send us your washer drawings or samples and target quantity — our engineers will confirm size range, coating, and price within one business day. WhatsApp: +86 185 6156 7088 for instant response and photo-based quoting.

Need a formal quotation? Send your Ductile Iron Square Flat Washer drawing, quantity and target price through our request for quotation form — it goes straight to the foundry inbox, and we reply with a priced offer, material certificate draft and production lead time within one business day.