---
title: "M12 USIT Rings (Self-Centring Bonded Seals) Dimensions"
description: "M12 USIT Rings (Self-Centring Bonded Seals): coarse thread pitch 1.75 mm."
url: https://engineeringhardware.com/guide/size/m12-usit-rings/
source: Engineering Hardware & Fasteners
---

# M12 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.

M12 USIT Rings (Self-Centring Bonded Seals) dimensions to Trade series (self-centring bonded washers, USIT type): coarse thread pitch 1.75 mm.

- **Coarse thread pitch:** 1.75 mm

Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering.

![M12 USIT Rings (Self-Centring Bonded Seals) Dimensions reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/USIT-Rings.webp)

Dimensional data for M12 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.

## M12 Dimensional Row (Trade series (self-centring bonded washers, USIT type))

| Thread | Seal element | Metal carrier | Typical service |
| --- | --- | --- | --- |
| M12 | 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 M12 USIT rings (self-centring bonded seals). A special seal is almost always a compound change rather than a size change — the same dimensions in a material that survives the medium.

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 M12 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

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## Applications & Industries for M12 USIT Rings

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/)

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 M12 for USIT Rings (Self-Centring Bonded Seals)?

For M12 the standard coarse pitch is 1.75 mm — this is the value used for USIT Rings (Self-Centring Bonded Seals).

### What clearance and tapping drill suit M12?

Use a 13.5 mm clearance hole (ISO 273 medium) for through-fixing, or a 10.25 mm tapping drill for a coarse M12 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