Buy Flat & Round Washers Online in Australia
Common Questions about Flat and Round Washers
What is a flat washer used for?
A flat washer is a plain ring placed under a bolt head or nut. Its job is to spread clamp load over a wider area, protecting the joint surface from indentation, distributing pressure on soft materials such as timber, alloy and plastic, and providing a smooth bearing face for the nut to turn against during tightening.
What is the difference between a flat washer and a spring washer?
A flat washer is plain and rigid — it spreads load across the joint face. A spring washer is split and twisted to act as a spring — it adds vibration resistance to the joint. Different jobs. A high-vibration joint typically uses both — flat washer under spring washer, both seated under the nut.
What sizes of flat washer are available?
Metric flat washers run from very small M2 sizes through to M30 and larger. Imperial sizes run from 3/16 inch to one inch and up. Each size has a nominal inside diameter matching the bolt thread, and an outside diameter — Form A is smaller and standard, Form B and C are larger for soft materials.
What materials are flat washers made of?
Workshop flat washers are commonly zinc-plated mild steel for general use. Stainless 304 and 316 variants serve corrosive, marine and food-grade applications. Brass, nylon and fibre washers are stocked for electrical, decorative and chemical applications. AIMS stocks the full common material range in metric and imperial sizes.
Do I need a washer under every bolt?
Best practice is yes — flat washers protect the surface and the bolt head from chewing into the workpiece. On critical or structural joints washers are mandatory. On low-load fastening into hard steel where galling is not a risk, washers may be omitted by design. Where in doubt, use the washer.
Flat Washer Sizes — Quick Reference
Flat washers are specified by bolt size (which sets the inside diameter), outside diameter (sets the load distribution area) and thickness. Form A (DIN 125 / AS 1237 narrow) is the workshop default; Form B (DIN 9021 wide) distributes load over a larger area; structural-rated washers (DIN 7349) take heavy load. Available in zinc-plated mild steel, 304/316 stainless, hot-dip galvanised and brass.
| Bolt Size | Form A (DIN 125 / Narrow) | Form B (DIN 9021 / Wide) | Standard |
|---|---|---|---|
| M3 | 3.2 × 7 × 0.5 mm | 3.2 × 9 × 0.8 mm | DIN 125A / DIN 9021 |
| M4 | 4.3 × 9 × 0.8 mm | 4.3 × 12 × 1.0 mm | DIN 125A / DIN 9021 |
| M5 | 5.3 × 10 × 1.0 mm | 5.3 × 15 × 1.2 mm | DIN 125A / DIN 9021 |
| M6 | 6.4 × 12 × 1.6 mm | 6.4 × 18 × 1.6 mm | DIN 125A / DIN 9021 |
| M8 | 8.4 × 16 × 1.6 mm | 8.4 × 24 × 2.0 mm | DIN 125A / DIN 9021 |
| M10 | 10.5 × 20 × 2.0 mm | 10.5 × 30 × 2.5 mm | DIN 125A / DIN 9021 |
| M12 | 13 × 24 × 2.5 mm | 13 × 37 × 3.0 mm | DIN 125A / DIN 9021 |
| M16 | 17 × 30 × 3.0 mm | 17 × 50 × 3.0 mm | DIN 125A / DIN 9021 |
| M20 | 21 × 37 × 3.0 mm | 22 × 60 × 4.0 mm | DIN 125A / DIN 9021 |
| M24 | 25 × 44 × 4.0 mm | 26 × 72 × 5.0 mm | DIN 125A / DIN 9021 |
Form A (narrow) is the standard workshop default. Use Form B (wide) under soft materials, slotted holes, or to better distribute load. For heavy structural use (HSFG bolts), use structural washers (DIN 6916 / AS 1252). Companion ranges: spring lock washers for vibration locking, star washers, full washers range.
Flat & Round Washers
Washers are simple but essential fastening components. Placed under a bolt head or nut, a flat washer distributes clamping load over a larger area, preventing the fastener from pulling through or embedding into the joined material under load. Washers also protect finished surfaces from damage during tightening and provide a smooth bearing surface under the fastener. AIMS Industrial supplies flat washers and round washers in steel, stainless steel, and galvanised finishes for industrial, construction, and engineering applications.
Types and Standards
- Form A washers (narrow/normal): Standard DIN 125A flat washers with an outside diameter approximately twice the bolt diameter. The most common general-purpose washer for machinery, fabrication, and structural work. Available in metric and imperial to suit standard bolt sizes.
- Form B washers (wide): Larger outside diameter than Form A for the same bolt size. Used where the substrate material is soft, compressible, or has a larger hole than standard — providing greater bearing area under the fastener.
- Heavy series washers: Thicker and stronger than standard washers. Specified where high clamping loads are applied and a standard washer would deform or where the washer must bridge a gap larger than normal.
- Structural washers (F436): Hardened washers to ASTM F436 for structural bolting applications. Required with Grade 8/8.8 and above structural bolts in steel construction.
Material Selection
Plain steel washers suit general indoor or protected applications. Hot-dip galvanised washers are specified for outdoor, exposed, and marine environments where corrosion resistance is needed. Grade 304 stainless washers are the standard for corrosive environments where a clean appearance is also required; Grade 316 stainless is specified where chloride exposure (coastal, marine, food processing) would cause crevice corrosion in 304. Matching the washer material to the bolt and nut material avoids galvanic corrosion at the joint.
Bulk and Bag Quantities
Washers are consumed in quantity on fabrication and construction projects. AIMS Industrial supplies washers in bag quantities for small jobs and in bulk for projects and maintenance departments that need a cost-effective ongoing supply. For the most commonly used sizes, we hold depth of stock to support same-day and next-day requirements. For bulk pricing or specific sizes, contact our team.
Bulk Supply for Projects
Washers are consumed in quantity on fabrication, construction, and maintenance projects. AIMS Industrial supplies flat washers in bag quantities for small jobs and in bulk for projects and maintenance departments with ongoing requirements. For high-volume or project-specific requirements — particular size combinations, material specifications, or large quantities on a specific timeline — our team can provide competitive pricing and confirm stock availability to meet project schedules.