---
title: "What Are Grade 5 UNF Fine-Thread Hex Nuts Used For?"
description: "Grade 5 UNF Fine-Thread Hex Nuts (ASME B18.2.2 / ASTM A563 / ASME B1.1) are used for the clamped counter-face of a bolted joint."
url: https://engineeringhardware.com/applications/grade-5-unf-fine-thread-hex-nuts/
source: Engineering Hardware & Fasteners
---

# What Are Grade 5 UNF Fine-Thread Hex Nuts Used For?

Nuts · ASME B18.2.2 / ASTM A563 / ASME B1.1 · Application guide

Typical applications, the industries that specify grade 5 unf fine-thread hex nuts, and how to choose the right size, material and finish for the joint.

Grade 5 UNF Fine-Thread Hex Nuts are used for the clamped counter-face of a bolted joint. They are manufactured to ASME B18.2.2 / ASTM A563 / ASME B1.1, and the choice of size, property class and finish is driven by the load in the joint and the environment it sits in.

- **Primary duty:** The clamped counter-face of a bolted joint
- **Governing standard:** ASME B18.2.2 / ASTM A563 / ASME B1.1
- **Category:** Nuts

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

![What Are Grade 5 UNF Fine-Thread Hex Nuts Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/09/Grade-5-UNF-Fine-Thread-Hex-Nuts.webp)

Grade 5 UNF Fine-Thread Hex Nuts are selected when an assembly calls for the clamped counter-face of a bolted joint. This application guide to the ASME B18.2.2 / ASTM A563 / ASME B1.1 type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better.

## Typical Applications for Grade 5 UNF Fine-Thread Hex Nuts

The most common settings where these are specified:

- **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment.
- **Maintenance & repair (MRO):** a stocked size for servicing existing plant where the original fastener spec must be matched.
- **Fabrication & metalwork:** bench and on-site assembly of steel frames, enclosures and weldments.
- **Bolted joints:** the clamping counter-face on studs and bolts across every assembly type.
- **Vibration-prone equipment:** where a locking or flanged style resists loosening.

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## How to Specify Grade 5 UNF Fine-Thread Hex Nuts for Your Application

- **Size:** Match the size to the mating part — see the dimension table below for each option.
- **Locking & grade:** Match the strength grade to the bolt, and choose a locking style (nyloc, all-metal, serrated flange) if the joint sees vibration.
- **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 ASME B18.2.2 / ASTM A563 / ASME B1.1. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

## Installation & Assembly Practice

- Run the nut down by hand before applying the wrench to catch cross-threading early.
- Tighten the nut rather than the bolt head where access allows — the torque-to-preload relation is more consistent.
- For locking styles, note that nyloc inserts are single-use in critical joints and lose grip above roughly 120 °C.

## Common Selection Mistakes with Grade 5 UNF Fine-Thread Hex Nuts

- Pairing a high-class bolt with a lower-class nut — the nut strips before the bolt reaches proof load; the nut class must meet or exceed the bolt class.
- Using a plain nut with a spring washer in severe vibration instead of a prevailing-torque locking nut.
- Re-using nyloc nuts in critical joints.

## Where Grade 5 UNF Fine-Thread Hex Nuts Are Not the Right Choice

Not on their own — they need a matching bolt or stud — and a plain nut is not a substitute for a locking type under heavy vibration.

Custom manufacturing · Made to drawing

## Need a grade 5 UNF fine-thread hex nuts outside the standard range?

Locking method is specifiable independently of the rest: nylon insert, all-metal deformed thread, serrated flange, or none. Made by cold heading or tapping.

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

[Custom nut manufacturing](https://engineeringhardware.com/custom/nuts/)[Send a drawing](https://engineeringhardware.com/custom/nuts/#rfq)

## Technical Drawing

Dimensioned line drawing of UNF fine Grade 5 UNF Fine-Thread Hex Nuts to ASME B18.2.2 / ASTM A563 / ASME B1.1. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Material:** medium carbon steel
- **Mating bolt grades:** Grade 5 or Grade 8 hex bolts
- **Finish options:** zinc plating or black oxide
- **Governing standards:** ASME B18.2.2 / ASTM A563

## Dimensions & Specifications (ASME B18.2.2 / ASTM A563 / ASME B1.1)

| Thread series | Material | Mating bolt grades | Finish options | Governing standards |
| --- | --- | --- | --- | --- |
| UNF fine | medium carbon steel | Grade 5 or Grade 8 hex bolts | zinc plating or black oxide | ASME B18.2.2 / ASTM A563 |
| UNF fine | medium carbon steel | Grade 5 hex bolts | zinc plating | ASME B1.1 thread form |

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 are Grade 5 UNF Fine-Thread Hex Nuts used for?

The clamped counter-face of a bolted joint. They are supplied to ASME B18.2.2 / ASTM A563 / ASME B1.1.

### Which industries use Grade 5 UNF Fine-Thread Hex Nuts?

They are commonly specified in vibration-prone equipment, frames & weldments and general machine building, among other sectors.

### How do I choose the right size of Grade 5 UNF Fine-Thread Hex Nuts?

Match the size to the mating part using the dimension table on this page.

### Do Grade 5 UNF Fine-Thread Hex Nuts need a locking feature?

If the joint sees vibration or cyclic load, use a locking style (nyloc, all-metal lock, or serrated flange) or a thread-locking adhesive. For static joints a standard nut tightened correctly is usually sufficient.

### Can I get a quote for Grade 5 UNF Fine-Thread Hex Nuts 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: [Grade 5 UNF Fine-Thread Hex Nuts — specifications & sizes](https://engineeringhardware.com/fastener/grade-5-unf-fine-thread-hex-nuts/)

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