Seals · Bonded Seal Rings

USIT Rings (Self-Centring Bonded Seals)

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.

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

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Sends the selected values to the quote form below.

Request a Quotation for USIT Rings (Self-Centring Bonded Seals)

The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

Request a Quotation

Specification

Item / category Standard Size(s) Material / finish Quantity

Business Information

Company * Contact Name * Email * Phone (with country code) Country / Region

Notes

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	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

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.

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.

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.
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.
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.
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.