--- title: "USIT Rings (Self-Centring Bonded Seals)" description: "USIT Rings (Self-Centring Bonded Seals) to Trade series (self-centring bonded washers, USIT type): full dimensional table." url: https://engineeringhardware.com/fastener/usit-rings/ source: Engineering Hardware & Fasteners --- # USIT Rings (Self-Centring Bonded Seals) Seals · Bonded Seal Rings 10 catalogued sizes, dimensioned to Trade series (self-centring bonded washers, USIT type). Pick any row and the technical drawing redraws to it. USIT Rings (Self-Centring Bonded Seals) to Trade series (self-centring bonded washers, USIT type): the full dimensional table is reproduced below. 10 sizes are held in the table below, and the technical drawing redraws to whichever row you select. - **Standard:** Trade series (self-centring bonded washers, USIT type) - **Catalogued sizes:** 10 Dimensions are nominal values from the governing standard. Confirm the tolerance class for your application before ordering. ![USIT Rings (Self-Centring Bonded Seals) technical product image](https://engineeringhardware.com/wp-content/uploads/2026/09/USIT-Rings.webp) Product catalog ## Related Bonded Seal Rings products [![High Hardness Q235 Paper Tape 34° Ring Handle Frame Wire Nail](https://img.engineeringhardware.com/High-Hardness-Q235-Paper-Tape-34-Ring-Handle-Frame-Wire-Nail.webp)](https://engineeringhardware.com/product/high-hardness-q235-paper-tape-34-ring-handle-frame-wire-nail/) Common, Ring-Shank & Specialty Nails ### [High Hardness Q235 Paper Tape 34° Ring Handle Frame Wire Nail](https://engineeringhardware.com/product/high-hardness-q235-paper-tape-34-ring-handle-frame-wire-nail/) Paper Stripe Nails · DIN, ANSI **US$1,199 – 1,679**MOQ 1,000 kilograms [![30 PCS Custom Size Galvanized Double Nail Pronged Truss Mending Plate Truss Gang Nail Plate](https://img.engineeringhardware.com/30-PCS-Custom-Size-Galvanized-Double-Nail-Pronged-Truss-Mending-Plate-Truss-Gang-Nail-Plate.webp)](https://engineeringhardware.com/product/30-pcs-custom-size-galvanized-double-nail-pronged-truss-mending-plate-truss-gang/) Common, Ring-Shank & Specialty Nails ### [30 PCS Custom Size Galvanized Double Nail Pronged Truss Mending Plate Truss Gang Nail Plate](https://engineeringhardware.com/product/30-pcs-custom-size-galvanized-double-nail-pronged-truss-mending-plate-truss-gang/) DIN, ANSI, GB, JIS, BSW · Steel **US$0.12 – 0.60**MOQ 1,000 pieces [![China Factory Direct Galvanized Duplex Head Nail Polished Double Head Nails with Cheap Price](https://img.engineeringhardware.com/China-Factory-Direct-Galvanized-Duplex-Head-Nail-Polished-Double-Head-Nails-with-Cheap-Price.webp)](https://engineeringhardware.com/product/china-factory-direct-galvanized-duplex-head-nail-polished-double-head-nails-with/) Common, Ring-Shank & Specialty Nails ### [China Factory Direct Galvanized Duplex Head Nail Polished Double Head Nails with Cheap Price](https://engineeringhardware.com/product/china-factory-direct-galvanized-duplex-head-nail-polished-double-head-nails-with/) Common Nail · ANSI, DIN, GB, ISO, JIS **US$720.00 – 960.00**MOQ 3 tons [![Vintage Round Head Upholstery Nails with Multi Color Gold Silver for Sofa Backrest](https://img.engineeringhardware.com/Vintage-Round-Head-Upholstery-Nails-with-Multi-Color-Gold-Silver-for-Sofa-Backrest.webp)](https://engineeringhardware.com/product/vintage-round-head-upholstery-nails-with-multi-color-gold-silver-for-sofa-backrest/) Common, Ring-Shank & Specialty Nails ### [Vintage Round Head Upholstery Nails with Multi Color Gold Silver for Sofa Backrest](https://engineeringhardware.com/product/vintage-round-head-upholstery-nails-with-multi-color-gold-silver-for-sofa-backrest/) Iron · Sofa,Leather Decor,Wooden Box,Door Decoration **Price on request**MOQ 1 piece [![High Sparkle Color Shift Polyester Craft Tumbler Nail Glitter Festival Decoration](https://img.engineeringhardware.com/High-Sparkle-Color-Shift-Polyester-Craft-Tumbler-Nail-Glitter-Festival-Decoration.webp)](https://engineeringhardware.com/product/high-sparkle-color-shift-polyester-craft-tumbler-nail-glitter-festival-decoration/) Common, Ring-Shank & Specialty Nails ### [High Sparkle Color Shift Polyester Craft Tumbler Nail Glitter Festival Decoration](https://engineeringhardware.com/product/high-sparkle-color-shift-polyester-craft-tumbler-nail-glitter-festival-decoration/) Christmas Decorations · Pet **US$5.98 – 43.18**MOQ 100 kilograms [![China High Quality Hot DIP Galvanized Felt Nails Anti Rust Steel](https://img.engineeringhardware.com/China-High-Quality-Hot-DIP-Galvanized-Felt-Nails-Anti-Rust-Steel.webp)](https://engineeringhardware.com/product/china-high-quality-hot-dip-galvanized-felt-nails-anti-rust-steel/) Common, Ring-Shank & Specialty Nails ### [China High Quality Hot DIP Galvanized Felt Nails Anti Rust Steel](https://engineeringhardware.com/product/china-high-quality-hot-dip-galvanized-felt-nails-anti-rust-steel/) Clout Nails · ANSI, DIN, GB, ISO, JIS **US$720.00 – 1,020**MOQ 3 tons [View all Common, Ring-Shank & Specialty Nails →](https://engineeringhardware.com/fastener-products/nails-staples-tacks/common-ring-shank-specialty-nails/) [Full product catalog](https://engineeringhardware.com/products/) ## Applications & Industries USIT Rings are bought for a small number of well-defined jobs. 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/) ## 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)) Every row below is a starting point for the customizer above — pick any size and the drawing will redraw to that row. | Thread | Seal element | Metal carrier | Typical service | | --- | --- | --- | --- | | [M6](https://engineeringhardware.com/guide/size/m6-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | [M8](https://engineeringhardware.com/guide/size/m8-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | [M10](https://engineeringhardware.com/guide/size/m10-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | [M12](https://engineeringhardware.com/guide/size/m12-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic ports and plugs | | [M14](https://engineeringhardware.com/guide/size/m14-usit-rings/) | NBR or FKM inner lip | zinc-plated or stainless | hydraulic and fuel | | [M16](https://engineeringhardware.com/guide/size/m16-usit-rings/) | NBR or FKM inner lip | zinc-plated or stainless | hydraulic and fuel | | [M18](https://engineeringhardware.com/guide/size/m18-usit-rings/) | NBR or FKM inner lip | zinc-plated or stainless | hydraulic | | [M20](https://engineeringhardware.com/guide/size/m20-usit-rings/) | NBR or FKM inner lip | zinc-plated or stainless | hydraulic | | [M22](https://engineeringhardware.com/guide/size/m22-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic | | [M27](https://engineeringhardware.com/guide/size/m27-usit-rings/) | NBR inner lip | zinc-plated steel | hydraulic | USIT Rings (Self-Centring Bonded Seals) are seals manufactured to Trade series (self-centring bonded washers, USIT type). This page lists the full dimensional range with the key specifications engineers need to select and specify them. ## What Are USIT Rings (Self-Centring Bonded Seals)? USIT Rings (Self-Centring Bonded Seals) are seals defined by Trade series (self-centring bonded washers, USIT type). They are selected by thread size and the dimensional characteristics shown below, and are available in a range of materials and finishes to suit the application and environment. ## Materials & Finishes O-rings and seals are specified by elastomer, not by steel grade: NBR (nitrile) for mineral oil and hydraulic service, FKM for higher temperature and aggressive chemistry, EPDM for water, steam and weathering, silicone for a wide temperature range in static duty, and PTFE where chemical resistance outweighs elastic recovery. Specify the compound, the hardness in Shore A and the temperature range alongside the dimensions. ## Specification Guides Each size, material and standard of USIT Rings (Self-Centring Bonded Seals) has its own reference page with the figures for that one configuration. ## Goes With Hardware commonly specified alongside USIT Rings (Self-Centring Bonded Seals). ## Pricing USIT Rings (Self-Centring Bonded Seals) are supplied to order. Pricing starts from approximately US$0.14 per piece for standard sizes in standard nitrile (NBR) 70 Shore A; final pricing depends on size, material, finish and order quantity (MOQ applies). Submit your exact configuration with the quote form above. Custom manufacturing · Made to drawing ## Need a USIT rings (self-centring bonded seals) outside the standard range? 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) 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 controlling standard for USIT Rings (Self-Centring Bonded Seals)? USIT Rings (Self-Centring Bonded Seals) are manufactured to Trade series (self-centring bonded washers, USIT type). The dimensional values on this page follow that standard. ### Which sizes of USIT Rings (Self-Centring Bonded Seals) does Engineering Hardware supply? The table on this page lists 10 sizes for USIT Rings (Self-Centring Bonded Seals), ranging from M6 to M27. Sizes outside the table can be quoted on request. ### In which materials are USIT Rings (Self-Centring Bonded Seals) supplied? USIT Rings (Self-Centring Bonded Seals) are supplied in NBR (nitrile), FKM, EPDM, silicone and PTFE, selected by fluid and temperature, with finishes including zinc plating, hot-dip galvanizing and black oxide. Choose material and finish to suit the load and the service environment for USIT Rings (Self-Centring Bonded Seals). ### How do I request a quotation? Use the parametric drawing on this page to set the exact configuration (size, material, finish) and click "Request this configuration" — a specialist from Engineering Hardware will respond within one business day.