--- title: "What Are Flat Washers Used For?" description: "Flat Washers (ISO 7089 / ISO 7093) are used for load distribution and anti-loosening under a bolt or nut. Catalogued M1.6 to M64." url: https://engineeringhardware.com/applications/flat-washers/ source: Engineering Hardware & Fasteners --- # What Are Flat Washers Used For? Washers · ISO 7089 / ISO 7093 · Application guide Typical applications, the industries that specify flat washers, and how to choose the right size, material and finish for the joint. Flat Washers are used for load distribution and anti-loosening under a bolt or nut. They are manufactured to ISO 7089 / ISO 7093, and selection is driven by the nominal bolt size, the fit and tolerance the assembly requires, and the service environment. - **Primary duty:** Load distribution and anti-loosening under a bolt or nut - **Governing standard:** ISO 7089 / ISO 7093 - **Nominal bolt size range:** M1.6 to M64 - **Category:** Washers Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation. ![What Are Flat Washers Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/06/Flat-Washers-—-ISO-7089-／-ISO-7093-Applications1.webp) Flat Washers are selected when an assembly calls for load distribution and anti-loosening under a bolt or nut. This application guide to the ISO 7089 / ISO 7093 type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better. Stocked across roughly M1.6 to M64, they cover general to heavy-duty work. ## Typical Applications for Flat Washers The most common settings where these are specified: - **Vibration applications:** spring and serrated types that maintain tension under cyclic load. - **Timber & soft materials:** large-OD types that prevent pull-through. - **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment. - **Maintenance & repair (MRO):** a stocked size for servicing existing plant where the original fastener spec must be matched. - **Fabrication & metalwork:** bench and on-site assembly of steel frames, enclosures and weldments. ## How to Specify Flat Washers for Your Application - **Size:** Match the nominal size to the mating thread or hole. This product spans M1.6–M64; check the full table below for the exact dimensions of each size. - **Type & OD:** Select flat for load spreading, spring/serrated for anti-loosening, or fender/large-OD for soft or oversized holes. - **Environment:** For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient. - **Standard:** This product is supplied to ISO 7089 / ISO 7093. Quoting the standard on your order guarantees interchangeable dimensions between suppliers. ## Installation & Assembly Practice - Place the washer under the rotating element (usually the nut) so tightening does not score the surface. - Chamfered-hole side of a hardened washer faces the bolt head fillet. - On serrated-flange hardware, do not add a plain washer — it defeats the serrations. ## Common Selection Mistakes with Flat Washers - Relying on a spring washer for locking on class 8.8+ joints — at high preload it flattens and adds nothing. - Choosing an OD too small for soft material, so the head pulls through or embeds. ## Where Flat Washers Are Not the Right Choice A washer does not replace a locking feature on its own in severe vibration, and a spring washer adds little clamp on high-strength joints. Custom manufacturing · Made to drawing ## Need a flat washers outside the standard range? Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom washer manufacturing](https://engineeringhardware.com/custom/washers/)[Send a drawing](https://engineeringhardware.com/custom/washers/#rfq) ## Technical Drawing Dimensioned line drawing of M1.6 Flat Washers to ISO 7089 / ISO 7093. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Inner diameter d1 min (mm):** 1.7 - **Outer diameter d2 max (mm):** 4.0 - **Thickness h (mm):** 0.3 ## Dimensions & Specifications (ISO 7089 / ISO 7093) | For bolt size | Inner diameter d1 min (mm) | Outer diameter d2 max (mm) | Thickness h (mm) | Reference standard | | --- | --- | --- | --- | --- | | M1.6 | 1.7 | 4.0 | 0.3 | ISO 7089 | | M2 | 2.2 | 5.0 | 0.3 | ISO 7089 | | M2.5 | 2.7 | 6.0 | 0.5 | ISO 7089 | | M3 | 3.2 | 7.0 | 0.5 | ISO 7089 | | M3.5 | 3.7 | 8.0 | 0.5 | ISO 7089 | | M4 | 4.3 | 9.0 | 0.8 | ISO 7089 | | M5 | 5.3 | 10.0 | 1.0 | ISO 7089 | | M6 | 6.4 | 12.0 | 1.6 | ISO 7089 | | M7 | 7.4 | 14.0 | 1.6 | ISO 7089 | | M8 | 8.4 | 16.0 | 1.6 | ISO 7089 | | M10 | 10.5 | 20.0 | 2.0 | ISO 7089 | | M12 | 13.0 | 24.0 | 2.5 | ISO 7089 | | M14 | 15.0 | 28.0 | 2.5 | ISO 7089 | | M16 | 17.0 | 30.0 | 3.0 | ISO 7089 | | M18 | 19.0 | 34.0 | 3.0 | ISO 7089 | | M20 | 21.0 | 37.0 | 3.0 | ISO 7089 | | M22 | 23.0 | 39.0 | 3.0 | ISO 7089 | | M24 | 25.0 | 44.0 | 4.0 | ISO 7089 | | M27 | 28.0 | 50.0 | 4.0 | ISO 7089 | | M30 | 31.0 | 56.0 | 4.0 | ISO 7089 | | M33 | 34.0 | 60.0 | 5.0 | ISO 7089 | | M36 | 37.0 | 66.0 | 5.0 | ISO 7089 | | M39 | 40.0 | 72.0 | 6.0 | ISO 7089 | | M42 | 43.0 | 78.0 | 7.0 | ISO 7089 | | M45 | 46.0 | 85.0 | 7.0 | ISO 7089 | | M48 | 50.0 | 92.0 | 8.0 | ISO 7089 | | M52 | 54.0 | 98.0 | 8.0 | ISO 7089 | | M56 | 58.0 | 105.0 | 9.0 | ISO 7089 | | M60 | 62.0 | 110.0 | 9.0 | ISO 7089 | | M64 | 66.0 | 115.0 | 9.0 | ISO 7089 | | M5 | 5.3 | 15.0 | 1.0 | ISO 7093 large series | | M6 | 6.4 | 18.0 | 1.6 | ISO 7093 large series | | M8 | 8.4 | 24.0 | 2.0 | ISO 7093 large series | | M10 | 10.5 | 30.0 | 2.5 | ISO 7093 large series | | M12 | 13.0 | 37.0 | 3.0 | ISO 7093 large series | | M16 | 17.0 | 50.0 | 3.0 | ISO 7093 large series | | M20 | 21.0 | 60.0 | 4.0 | ISO 7093 large series | | M24 | 25.0 | 72.0 | 5.0 | ISO 7093 large series | Inside the plant ## Manufactured in our own plant This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided. 1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift. 2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g. 3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1. 4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227. ## Frequently Asked Questions ### What material should Flat Washers be for outdoor use? For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate. ### Are Flat Washers made to a recognized standard? Yes — they are manufactured to ISO 7089 / ISO 7093, so dimensions are interchangeable between suppliers when you quote the standard on your order. ### What are Flat Washers used for? Load distribution and anti-loosening under a bolt or nut. They are supplied to ISO 7089 / ISO 7093. ### Which industries use Flat Washers? They are commonly specified in general machine building, maintenance & repair (mro) and fabrication & metalwork, among other sectors. ### Can I get a quote for Flat Washers in the size and material I need? Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time. ## Related Pages Product page: [Flat Washers — specifications & sizes](https://engineeringhardware.com/fastener/flat-washers/) ### Flat Washers Specification Guides ### Related Fastener Applications