---
title: "What Are Unthreaded Round Spacers Used For?"
description: "Unthreaded Round Spacers (Trade series (plain bore spacer)) are used for setting a fixed distance on a screw that passes straight through it, with no thread…"
url: https://engineeringhardware.com/applications/unthreaded-round-spacers/
source: Engineering Hardware & Fasteners
---

# What Are Unthreaded Round Spacers Used For?

Standoffs & Spacers · Trade series (plain bore spacer) · Application guide

Typical applications, the industries that specify unthreaded round spacers, and how to choose the right size, material and finish for the joint.

Unthreaded Round Spacers are used for setting a fixed distance on a screw that passes straight through it, with no thread of its own. They are manufactured to Trade series (plain bore spacer), and selection is driven by the bore diameter, the fit and tolerance the assembly requires, and the service environment.

- **Primary duty:** Setting a fixed distance on a screw that passes straight through it, with no thread of its own
- **Governing standard:** Trade series (plain bore spacer)
- **Bore diameter range:** 3.2 mm to 6.4 mm
- **Category:** Standoffs & Spacers

Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation.

![What Are Unthreaded Round Spacers Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/08/Unthreaded-Spacers.webp)

Unthreaded Round Spacers are selected when an assembly calls for setting a fixed distance on a screw that passes straight through it, with no thread of its own. This application guide to the Trade series (plain bore spacer) type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better. Stocked across roughly 3.2 mm to 6.4 mm, they cover general to heavy-duty work.

## Typical Applications for Unthreaded Round Spacers

The most common settings where these are specified:

- **Fabrication & metalwork:** bench and on-site assembly of steel frames, enclosures and weldments.
- **Electronics assembly:** holding boards off a chassis and stacking multiple boards at a fixed pitch.
- **Enclosures & panels:** spacing a fascia, guard or label plate off the surface behind it.
- **Machine alignment:** setting and correcting the height of a component on its mounting.
- **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment.

Product catalog

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## How to Specify Unthreaded Round Spacers for Your Application

- **Size:** Select on bore diameter, and confirm it against the mating feature in the assembly. This product spans 3.2 mm–6.4 mm; check the full table below for the exact dimensions of each size.
- **Material:** Choose the material and finish for the service environment — plated steel for general use, stainless for corrosion resistance.
- **Environment:** For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- **Standard:** This product is supplied to Trade series (plain bore spacer). Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

## Where Unthreaded Round Spacers Are Not the Right Choice

Match the fastener to the load, environment and whether the joint must be reopened; the wrong class or style is the usual cause of joint failure.

Custom manufacturing · Made to drawing

## Need a unthreaded round spacers outside the standard range?

Dimensions, material, finish and form are specified from the drawing — a standoff & spacer outside the standard range is a variation on existing tooling rather than a new design. Made by tapping or turning.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom standoff & spacer manufacturing](https://engineeringhardware.com/custom/standoffs-spacers/)[Send a drawing](https://engineeringhardware.com/custom/standoffs-spacers/#rfq)

## Technical Drawing

Dimensioned line drawing of 3.2 Unthreaded Round Spacers to Trade series (plain bore spacer). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Outer diameter (mm):** 6.0
- **Length L (mm):** 5
- **Clears screw:** M3
- **Material:** Aluminium
- **Finish:** Plain
- **Tolerance on length:** u00b10.2 mm

## Dimensions & Specifications (Trade series (plain bore spacer))

| Bore d1 (mm) | Outer diameter (mm) | Length L (mm) | Clears screw | Material | Finish | Tolerance on length |
| --- | --- | --- | --- | --- | --- | --- |
| 3.2 | 6.0 | 5 | M3 | Aluminium | Plain | u00b10.2 mm |
| 3.2 | 6.0 | 10 | M3 | Aluminium | Plain | u00b10.2 mm |
| 3.2 | 6.0 | 20 | M3 | Nylon 6/6 | Natural | u00b10.3 mm |
| 4.2 | 8.0 | 10 | M4 | Brass | Nickel | u00b10.2 mm |
| 4.2 | 8.0 | 25 | M4 | Aluminium | Anodised | u00b10.2 mm |
| 5.2 | 10.0 | 15 | M5 | Aluminium | Anodised | u00b10.2 mm |
| 6.4 | 12.0 | 20 | M6 | Stainless | Passivated | u00b10.2 mm |

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 material should Unthreaded Round Spacers be for outdoor use?

For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate.

### Are Unthreaded Round Spacers made to a recognized standard?

Yes — they are manufactured to Trade series (plain bore spacer), so dimensions are interchangeable between suppliers when you quote the standard on your order.

### What are Unthreaded Round Spacers used for?

Setting a fixed distance on a screw that passes straight through it, with no thread of its own. They are supplied to Trade series (plain bore spacer).

### Which industries use Unthreaded Round Spacers?

They are commonly specified in general machine building, maintenance & repair (mro) and fabrication & metalwork, among other sectors.

### Can I get a quote for Unthreaded Round Spacers in the size and material I need?

Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time.

## Related Pages

Product page: [Unthreaded Round Spacers — specifications & sizes](https://engineeringhardware.com/fastener/unthreaded-round-spacers/)

### Unthreaded Round Spacers Specification Guides

### Related Fastener Applications