M16 (5/8") x 33.5mm x 2.75mm Plain Black Uncoated Heavy Washers Low Tensile HEC Standard

About Flat Round Washers

Flat Round Washers spread bolt or nut clamping load over a wider bearing area than the bolt head alone, protect the work face from rotation marks during install, and bridge slightly oversized or imperfect holes. The default washer for almost every bolted joint. Supplied across the full BNA range of finishes (stainless A2 and A4, zinc plated, galvanised, brass, nylon) to HEC Standard, DIN 9021 (large OD / fender) and other variants.

Recommended use Indoor, oiled or sacrificial-wear applications where the fastener is replaced periodically. Common in machinery internals, ground-engaging equipment subject to wear, and any high-tensile assembly that will be painted, oiled or sealed after install.

Frequently Asked Questions

Material & Coating

Plain Black Uncoated Carbon steel. No corrosion protection. The dark colour is a thin oxide layer from the heat treatment process, not a corrosion barrier. Appearance varies from light grey to dark black across batches due to the heat treatment process, so colour consistency is not guaranteed between orders.

Important Will corrode rapidly in any wet or humid environment. NOT suitable for outdoor or coastal use without a separate coating.

Class Metric fasteners are classified as class 2, 4.6, 8.8, 10.9, 12.9, 14.9. See the head marking chart and full strength table.

How to Order the Right Size Washer

Washer sizing Washer sizes can be confusing, so here is the quickest way to find the right one. If you already have a bolt or screw, match the bolt size: an M6 bolt takes an M6 washer, M10 takes M10, and so on. Look for the size at the start of the description (e.g. 'M6 Flat Round Washer').

If you only have a loose washer to match, measure the inside diameter and pick the next size down. The washer's inside is always slightly larger than the matching bolt so it slides on freely. For example, an inside measurement of approximately 6.50mm means you need an M6 washer; 17.25mm means you need an M16 washer.

The outside diameter is measured outside-to-outside. Thickness varies between batches - washers are not precision-made fasteners and slight variations are normal. All published measurements on this site should be used as a guide only.

Need every size? See our full washer gauge sizing chart for the complete SWG range (8g to 24g) in mm and inch.

Resources

Pricing & Delivery

Includes GST, a Tax Invoice and Free Standard Delivery anywhere in Australia.

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Disclaimer

Technical data Researched and compiled from numerous industry sources for the sole purpose of providing basic information. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person, and Bolt and Nut Australia is not responsible for any loss, claim or damages arising therefrom. In developing this information, Bolt and Nut Australia has made a determined effort to present it accurately.

Measurements Sizes are taken from supplier catalogues or hand-measured and should be used as a guide. Minor variation between batches is normal. Stock is sourced from various suppliers, so differences may exist between batches in markings, appearance or finish.

Product Photos & PDF Data Sheets Represent the product type, not exact size. PDFs are a reference guide only. Specifications may change without notice.

If you see any problems with any of our specifications or you require additional information please contact us.