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Bolts · ASME B18.3

A2 (304) Stainless Steel Inch Hex-Socket Shoulder Screws

Mechanical properties, corrosion behaviour and the full dimensional range for this grade.

A2 Stainless Steel Inch Hex-Socket Shoulder Screws are supplied to ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70. Corrosion behaviour is good general corrosion resistance, the material is largely non-magnetic, and the usable service range is approx. -200 °C to +400 °C, subject to the property class and the joint. In practice this grade is the most common stainless group for indoor and general outdoor fasteners.

Grade
ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70
Corrosion resistance
Good general corrosion resistance
Magnetic response
Largely non-magnetic
Service temperature
approx. -200 °C to +400 °C, subject to the property class and the joint

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

A2 (304) Stainless Steel Inch Hex-Socket Shoulder Screws reference image

A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is the most common stainless group for indoor and general outdoor fasteners. When inch hex-socket shoulder screws are specified in this grade, the dimensions remain per ASME B18.3; the material determines corrosion behavior (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint). Both are covered below with the size table.

Why Choose A2 Stainless Steel for Inch Hex-Socket Shoulder Screws

The most common stainless group for indoor and general outdoor fasteners. For inch hex-socket shoulder screws, this matters when good general corrosion resistance is the primary requirement.

Mechanical & Physical Properties

Grade designationISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70
Magnetic responseLargely non-magnetic
Service temperatureapprox. -200 °C to +400 °C, subject to the property class and the joint
Corrosion characteristicGood general corrosion resistance

Galvanic & Galling Considerations

Two important notes for stainless inch hex-socket shoulder screws: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.

Comparable Grades

For Inch Hex-Socket Shoulder Screws, the alternative stainless grade is A4 (316). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.

Using Stainless Fasteners in Aluminum

Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.

Sizes of Inch Hex-Socket Shoulder Screws Available in A2 Stainless Steel

Shoulder diameter (in)Shoulder length (in)Hex socket across-flats (in)Thread seriesMaterial optionsReference standard
1/81/8~1-1/25/64~1/4#4-40 through #10-32alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
1/41/8~1-1/25/64~1/4#4-40 through 1/4-20alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
1/21/8~1-1/25/64~1/4#4-40 through 3/8-16alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
3/41/8~1-1/25/64~1/41/4-20 through 1/2-13alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3

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.

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Specification
Business Information

Dimensions & Specifications (ASME B18.3)

Shoulder diameter (in)Shoulder length (in)Hex socket across-flats (in)Thread seriesMaterial optionsReference standard
1/81/8~1-1/25/64~1/4#4-40 through #10-32alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
1/41/8~1-1/25/64~1/4#4-40 through 1/4-20alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
1/21/8~1-1/25/64~1/4#4-40 through 3/8-16alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3
3/41/8~1-1/25/64~1/41/4-20 through 1/2-13alloy steel / 303-316 stainless / 416 stainless / brassASME B18.3

Applications & Industries

The sectors that buy Inch Hex-Socket Shoulder Screws to ASME B18.3, and the duty each one buys them for. Stocked from 1/8 to 3/4 (screw size).

Industries that specify Inch Hex-Socket Shoulder Screws

  • Die and mold tooling Guide points where the cylindrical shoulder must be held to size.
  • Test fixtures Replaceable stops and locating posts inside compact assemblies.
  • Machine guards Recessed shoulder hardware where a socket driver clears the surrounding plate.
  • Robotic linkages Socket-head shoulder screws used as repeatable pivots.
  • Automotive & transport Chassis, driveline and body fixings that see vibration and are assembled to a controlled preload.
  • Steel fabrication Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.

Typical applications

  • placing the head in a counterbore while the shoulder carries the part
  • specifying shoulder length, diameter and mating thread independently
  • using a positive socket drive where a slot would cam out
  • providing a controlled shoulder bearing surface with a hex socket head
  • bolting brackets, motors and gearboxes to a frame
  • assemblies that are dismantled for service and re-torqued

Service conditions to specify against

Marine and coastal
Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
High load
Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
Torque and preload
The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.

Where to use something else

  • Do not let the mating load run on the thread or socket head; the shoulder is the intended bearing feature.
  • Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.

Full application guide: where Inch Hex-Socket Shoulder Screws are used, how to specify them, and the cases they are wrong for

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

Can A2 Stainless Steel Inch Hex-Socket Shoulder Screws gall during installation?

Yes — stainless on stainless is prone to thread galling under load, especially at smaller sizes. Use an anti-galling lubricant or wax thread compound, and slow the tightening rate where possible.

Is A2 Stainless Steel food-grade?

A2 (304) is widely accepted for food contact in non-chloride environments; A4 (316) is preferred where chlorides are present.

Can A2 Stainless Steel Inch Hex-Socket Shoulder Screws be used with aluminum?

Yes, but stainless drives mild galvanic corrosion of aluminum in wet service — isolate with a coating, sleeve or paint, or accept the trade-off if the joint is dry and indoor.

What's the service temperature limit for A2 Stainless Steel?

The practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint.

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.