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Nuts · ASME B18.2.2 · Application guide

What Are Slotted Hex Nuts, UNC Used For?

Typical applications, the industries that specify slotted hex nuts, unc, and how to choose the right size, material and finish for the joint.

Slotted Hex Nuts, UNC are used for inch slotted hex nuts with UNC thread, locked with a cotter pin. They are manufactured to ASME B18.2.2, 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
Inch slotted hex nuts with UNC thread, locked with a cotter pin
Governing standard
ASME B18.2.2
Screw size range
1 1/2" to 9/16"
Category
Nuts

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

What Are Slotted Hex Nuts, UNC Used For? application image

Slotted Hex Nuts, UNC (ASME B18.2.2) are specified where the joint requires inch slotted hex nuts with UNC thread, locked with a cotter pin. The sections below cover the typical end-uses by industry, the size and material decisions for each, assembly practice, and the applications this fastener type is not suited to. Stocked across roughly 1 to 9, they cover general to heavy-duty work.

Typical Applications for Slotted Hex Nuts, UNC

The most common settings where these are specified:

  • Automotive: axle nuts.
  • Agriculture: pivot pins.
  • Aircraft ground: linkages.
  • Trailers: wheel bearings.

How to Specify Slotted Hex Nuts, UNC for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans 1–9; check the full table below for the exact dimensions of each size.
  • 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. 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 Slotted Hex Nuts, UNC

  • 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 Slotted Hex Nuts, UNC 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 slotted hex nuts, UNC 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 manufacturingSend a drawing

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.

Dimensioned line drawing of 1/4" Slotted Hex Nuts, UNC to ASME B18.2.2. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.
Threads per inch
20
Width across flats s (in)
0.438
Nut height m (in)
0.219
T (in)
0.13
S (in)
0.085
Sends the selected values to the quote form below.

Request a Quote

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

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Specification
Business Information

Dimensions & Specifications (ASME B18.2.2)

SizeThreads per inchWidth across flats s (in)Nut height m (in)T (in)S (in)Reference standard
1/4"200.4380.2190.130.085ASME B18.2.2
5/16"180.50.2660.170.105ASME B18.2.2
3/8"160.5620.3280.20.135ASME B18.2.2
7/16"140.6880.3750.220.135ASME B18.2.2
1/2"130.750.4380.280.165ASME B18.2.2
9/16"120.8750.4840.30.165ASME B18.2.2
5/8"110.9380.5470.330.21ASME B18.2.2
3/4"101.1250.6410.390.21ASME B18.2.2
7/8"91.3120.750.5050.21ASME B18.2.2
1"81.50.8590.5750.27ASME B18.2.2
1 1/8"71.6880.9690.6250.285ASME B18.2.2
1 1/4"71.8751.0620.6850.355ASME B18.2.2
1 3/8"62.0621.1720.80.355ASME B18.2.2
1 1/2"62.251.2810.840.415ASME B18.2.2
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
    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
    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
    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
    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 Slotted Hex Nuts, UNC 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 Slotted Hex Nuts, UNC made to a recognized standard?

Yes — they are manufactured to ASME B18.2.2, so dimensions are interchangeable between suppliers when you quote the standard on your order.

What are Slotted Hex Nuts, UNC used for?

Inch slotted hex nuts with UNC thread, locked with a cotter pin. They are supplied to ASME B18.2.2.

Which industries use Slotted Hex Nuts, UNC?

They are commonly specified in aircraft ground, trailers and automotive, among other sectors.

Can I get a quote for Slotted Hex Nuts, UNC 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.