--- title: "M8 Insulating Fibre Washers Dimensions" description: "M8 Insulating Fibre Washers: inside diameter 8.4 mm, outside diameter 16 mm, thickness 1 mm." url: https://engineeringhardware.com/guide/size/m8-insulating-fibre-washers/ source: Engineering Hardware & Fasteners --- # M8 Insulating Fibre Washers Dimensions Washers · Trade series (vulcanised fibre washer) Controlling dimensions to Trade series (vulcanised fibre washer), with tolerances and fit. M8 Insulating Fibre Washers dimensions to Trade series (vulcanised fibre washer): inside diameter 8.4 mm, outside diameter 16 mm, thickness 1 mm. - **Inside diameter:** 8.4 mm - **Outside diameter:** 16 mm - **Thickness:** 1 mm Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering. ![M8 Insulating Fibre Washers Dimensions reference image](https://engineeringhardware.com/wp-content/uploads/2026/08/Insulating-Washers.webp) M8 Insulating Fibre Washers (Trade series (vulcanised fibre washer)): the row from the product table, what the nominal bolt size controls in the assembly, and the notes that matter when specifying this size. ## M8 Dimensional Row (Trade series (vulcanised fibre washer)) | For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Dielectric strength (kV/mm) | Max temperature (u00b0C) | Material | Moisture | | --- | --- | --- | --- | --- | --- | --- | --- | | M8 | 8.4 | 16.0 | 1.0 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | ## Mating Parts for M8 A M8 flat washer pairs with a M8 bolt/screw and matching M8 nut. Custom manufacturing · Made to drawing ## Need insulating fibre washers in a size this table does not list? This page covers M8 insulating fibre washers. 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 M8 Insulating Fibre Washers to Trade series (vulcanised fibre washer). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Inner diameter d1 (mm):** 8.4 - **Outer diameter d2 (mm):** 16.0 - **Thickness t (mm):** 1.0 - **Dielectric strength (kV/mm):** 10 - **Max temperature (u00b0C):** 105 - **Material:** Vulcanised fibre - **Moisture:** Hygroscopic u2014 indoor use ## Dimensions & Specifications (Trade series (vulcanised fibre washer)) | For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Dielectric strength (kV/mm) | Max temperature (u00b0C) | Material | Moisture | | --- | --- | --- | --- | --- | --- | --- | --- | | M3 | 3.2 | 7.0 | 0.5 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | | M4 | 4.3 | 9.0 | 0.5 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | | M5 | 5.3 | 10.0 | 0.8 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | | M6 | 6.4 | 12.0 | 0.8 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | | M8 | 8.4 | 16.0 | 1.0 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | | M10 | 10.5 | 20.0 | 1.0 | 10 | 105 | Vulcanised fibre | Hygroscopic u2014 indoor use | Product catalog ## 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Applications & Industries for M8 Insulating Fibre Washers The sectors that buy Insulating Fibre Washers, and the duty each one buys them for. Stocked from M3 to M10 (nominal bolt size). ### Industries that specify Insulating Fibre Washers - **Food & pharma equipment:** Non-marking, non-contaminating washers in washdown areas. - **Electrical & electronics:** Insulating and isolating fixings in panels and boards. - **Chemical & process:** Chemically resistant seating under a fastener. - **Machine building & OEM:** Setting bearing area on soft alloy, plastic and oversized holes. - **Timber & construction:** Large-diameter washers that stop pull-through in softer material. - **Rotating & vibrating plant:** Spring, tooth and wedge types that maintain or lock bolt tension. ### Typical applications - protecting a soft or finished surface under a head - insulating a fastener electrically from the panel - separating dissimilar metals to break a galvanic cell - maintaining bolt tension in a joint that settles - spreading clamp load over a soft or oversized bearing face - protecting a painted or plated surface under a turned nut ### Service conditions to specify against - **Marine and coastal:** Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit. - **Hardness matters:** Under a high-strength bolt a soft washer embeds into the joint and preload is lost — specify a hardened washer for structural bolting. [Full application guide: where Insulating Fibre Washers are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/insulating-fibre-washers/) 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 ### Which washer dimensions matter most for M8? For a flat washer, the outside diameter (the bearing surface) and the thickness control how the load is spread under the head and how much elastic preload is preserved. The inside diameter must clear the bolt body but not be so large that the head bears mostly on the washer's outer rim. ### What is the coarse-thread pitch of M8 for Insulating Fibre Washers? For M8 the standard coarse pitch is 1.25 mm — this is the value used for Insulating Fibre Washers. ### What clearance and tapping drill suit M8? Use a 9 mm clearance hole (ISO 273 medium) for through-fixing, or a 6.75 mm tapping drill for a coarse M8 thread. ### How do I request a quotation? Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day. ## Related Pages [View the full Insulating Fibre Washers page](https://engineeringhardware.com/fastener/insulating-fibre-washers/) ### More Insulating Fibre Washers Guides