A4 Stainless Steel Oval-Head Machine Screws are supplied to ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80. Corrosion behaviour is superior, including marine and chloride environments, 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 specified for marine, coastal and chemical applications.
- Grade
- ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
- Corrosion resistance
- Superior, including marine and chloride environments
- 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.
Material specification page for oval-head machine screws in A4 Stainless Steel. Covers the grade designation (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.6.3.
Why Choose A4 Stainless Steel for Oval-Head Machine Screws
Specified for marine, coastal and chemical applications. For oval-head machine screws, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
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| Magnetic response | Largely non-magnetic |
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| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
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| Corrosion characteristic | Superior, including marine and chloride environments |
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Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Oval-Head Machine Screws in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Oval-Head Machine Screws, the alternative stainless grade is A2 (304). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
Using Stainless Fasteners in Aluminum
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Oval-Head Machine Screws Available in A4 Stainless Steel
| Size example | Length (in) | Drive | Head form | Material options | Reference standard |
|---|
| #8-32 | 2 | Phillips | oval raised countersunk | 18-8 stainless steel / steel | ASME B18.6.3 |
| inch machine-screw sizes | | Phillips | oval raised countersunk | 18-8 stainless steel / steel | ASME B18.6.3 |
Dimensions are independent of the material: every size above is available in A4 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom screw manufacturingSend a drawing
Applications & Industries
Oval-Head Machine Screws are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from #8-32 to inch machine-screw sizes (nominal diameter).
Industries that specify Oval-Head Machine Screws
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Light fabrication
ASME B18.6.3 sizes fit inch machine-screw joints.
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Visible equipment
Oval heads provide a finished raised profile on covers and trim.
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Instrument panels
Phillips drive supports routine assembly in a low-profile raised seat.
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Appliance housings
Stainless and steel options match the enclosure material.
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Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
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Maintenance & MRO
Stocked replacements matched to an existing property class, thread and finish.
Typical applications
- selecting steel or 18-8 stainless
- seating a raised oval head on a prepared countersink
- choosing the under-head length for the panel stack
- using a Phillips driver on a visible machine screw
- joints where the property class is stated on the drawing
- clamping two machined faces to a calculated preload
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 use an oval head in a flat-bottom counterbore; the raised profile needs its matching seat.
- 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 Oval-Head Machine Screws are used, how to specify them, and the cases they are wrong for
