--- title: "M6 USIT Rings (Self-Centring Bonded Seals) Dimensions" description: "M6 USIT Rings (Self-Centring Bonded Seals): coarse thread pitch 1 mm." url: https://engineeringhardware.com/guide/size/m6-usit-rings/ source: Engineering Hardware & Fasteners --- # M6 USIT Rings (Self-Centring Bonded Seals) Dimensions Seals · Trade series (self-centring bonded washers, USIT type) Controlling dimensions to Trade series (self-centring bonded washers, USIT type), with tolerances and fit. M6 USIT Rings (Self-Centring Bonded Seals) dimensions to Trade series (self-centring bonded washers, USIT type): coarse thread pitch 1 mm. - **Coarse thread pitch:** 1 mm Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering. ![M6 USIT Rings (Self-Centring Bonded Seals) Dimensions reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/USIT-Rings.webp) Dimensional data for M6 USIT Rings (Self-Centring Bonded Seals) to Trade series (self-centring bonded washers, USIT type), with the installation notes for this type. Values are taken from the governing standard rather than from a general machine-thread table, because this type is not selected on one. ## M6 Dimensional Row (Trade series (self-centring bonded washers, USIT type)) | Thread | Seal element | Metal carrier | Typical service | | --- | --- | --- | --- | | M6 | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | Custom manufacturing · Made to drawing ## Need USIT rings (self-centring bonded seals) in a size this table does not list? This page covers M6 USIT rings (self-centring bonded seals). Inside diameter, cross-section and compound are the three that matter, and the compound is chosen against the fluid and the temperature rather than the dimensions. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom seal manufacturing](https://engineeringhardware.com/custom/seals/)[Send a drawing](https://engineeringhardware.com/custom/seals/#rfq) ## Technical Drawing Dimensioned line drawing of M6 USIT Rings (Self-Centring Bonded Seals) to Trade series (self-centring bonded washers, USIT type). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Seal element:** NBR inner lip - **Metal carrier:** zinc-plated steel - **Typical service:** hydraulic ports and plugs ## Dimensions & Specifications (Trade series (self-centring bonded washers, USIT type)) | Thread | Seal element | Metal carrier | Typical service | | --- | --- | --- | --- | | M6 | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | M8 | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | M10 | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | M12 | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | M14 | NBR or FKM inner lip | zinc-plated or stainless | hydraulic and fuel | | M16 | NBR or FKM inner lip | zinc-plated or stainless | hydraulic and fuel | | M18 | NBR or FKM inner lip | zinc-plated or stainless | hydraulic | | M20 | NBR or FKM inner lip | zinc-plated or stainless | hydraulic | | M22 | NBR inner lip | zinc-plated steel | hydraulic | | M27 | NBR inner lip | zinc-plated steel | hydraulic | Product catalog ## Related Bonded Seal Rings products [![3 in. 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These are the ones we ship them for. Stocked from M6 to M27. ### Industries that specify USIT Rings - **Machine tools:** Coolant and hydraulic ports. - **Hydraulics:** Port plugs and fittings. - **Mobile plant:** Vibration-prone joints. - **Compressors:** Sealing under pressure cycling. - **Process & food equipment:** Sealing at joints that are cleaned and inspected. - **Hydraulics & pneumatics:** Static and dynamic sealing in cylinders and valve bodies. ### Typical applications - seating the ring square before tightening - choosing the self-centring form where the seat is imperfect - matching the thread size exactly - selecting FKM where the fluid or temperature demands it - excluding dust and moisture from a housing - sealing a joint against fluid or air pressure ### Service conditions to specify against - **Sealed joints:** Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life. ### Where to use something else - Do not reuse a bonded or USIT seal after it has been compressed; the elastomer has taken a set and will not seal a second time. [Full application guide: where USIT Rings are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/usit-rings/) 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 is the coarse-thread pitch of M6 for USIT Rings (Self-Centring Bonded Seals)? For M6 the standard coarse pitch is 1 mm — this is the value used for USIT Rings (Self-Centring Bonded Seals). ### What clearance and tapping drill suit M6? Use a 6.6 mm clearance hole (ISO 273 medium) for through-fixing, or a 5 mm tapping drill for a coarse M6 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 USIT Rings (Self-Centring Bonded Seals) page](https://engineeringhardware.com/fastener/usit-rings/) ### More USIT Rings (Self-Centring Bonded Seals) Guides