A2 Stainless Steel Phillips Countersunk Machine Screws — Rust-Resistant, Flush-Mount, UNC Thread
Zinc-plated screws rust. Painted screws chip. When your project needs a fastener that stays clean, holds firm, and sits perfectly flush — whether it’s an outdoor enclosure, a marine-adjacent fixture, or a precision electronics build — you need A2 stainless steel Phillips countersunk machine screws that won’t let you down over time. These are built for makers, fabricators, maintenance techs, and DIYers who refuse to compromise on corrosion resistance.
Each pack contains Phillips flat head machine screws in your selected UNC size and quantity (50 or 100 pieces per pack depending on diameter). Screws are manufactured from A2 stainless steel (304 grade), featuring a 82° countersunk flat head profile standard to UNC inch fasteners, and a Phillips cross drive recess. Available in five UNC thread sizes — #4-40, #6-32, #8-32, #10-24, and 1/4-20 — with lengths ranging from 3/16” to 1-1/2” depending on the diameter selected.
These stainless flat head machine screws are well suited for mounting electronics and control panels where a flush, corrosion-free surface is essential; securing outdoor signage, enclosures, and fixtures exposed to moisture; and fastening structural brackets and hardware in workshops, HVAC systems, and light industrial equipment where UNC stainless machine screws are the specified fastener.
🔩 Thread Standard: Unified National Coarse (UNC) — #4-40 (40 TPI), #6-32 (32 TPI), #8-32 (32 TPI), #10-24 (24 TPI), 1/4-20 (20 TPI). Compatible with standard UNC nuts, threaded inserts, and tapped holes per ASME B1.1.
✅ Key Features of These A2 Stainless Phillips Countersunk Machine Screws
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🥊A2 Stainless Steel (304 Grade) — Provides substantially better corrosion resistance than zinc-plated carbon steel, making these stainless flat head machine screws suitable for outdoor, humid, and mildly corrosive environments.
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⬇️Flush-Mount Countersunk Head — The flat head tapers to sit flush with or below the material surface when installed in a countersunk hole, eliminating snag points on panels, enclosures, and structural faces.
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✚️Phillips Cross Drive — Compatible with PH1 (#4–#6) and PH2 (#8–1/4-20) bits for fast installation with standard power drivers, reducing hand fatigue on bulk fastening jobs.
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📐Five UNC Sizes in One Listing — #4-40 through 1/4-20 covers the most common UNC machine screw sizes used in US electronics, appliances, and mechanical assemblies, reducing the number of separate SKUs to manage.
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📦Bulk Packs of 50 or 100 Pieces — Sized for production runs, workshop restocking, and repair kits; larger packs reduce per-unit cost for repeat stainless countersunk screw applications.
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⚙️ASME B1.1 UNC Thread Compatibility — Threads conform to the Unified National Coarse standard, ensuring reliable fit with off-the-shelf UNC nuts, threaded inserts, and pre-tapped holes without custom tooling.
📐 Technical Specifications — A2 Stainless Phillips Flat Head Machine Screws
| Product Type |
Phillips Countersunk (Flat Head) Machine Screw |
| Drive Type |
Phillips (Cross) — PH1 / PH2 |
| Head Style |
Countersunk / Flat Head (flush-mount) |
| Head Angle |
82° (UNC inch standard) |
| Material |
A2 Stainless Steel (304 Grade) |
| Thread Standard |
UNC — Unified National Coarse (ASME B1.1) |
| Available Sizes |
#4-40, #6-32, #8-32, #10-24, 1/4-20 |
| Thread Pitch |
#4-40: 40 TPI | #6-32: 32 TPI | #8-32: 32 TPI | #10-24: 24 TPI | 1/4-20: 20 TPI |
| Available Lengths |
3/16” to 1-1/2” — See variant options |
| Packing Quantity |
#4-40: 100 pcs | #6 through 1/4-20: 50 pcs |
| Tensile Strength |
Typically 500–700 MPa (A2-70 grade) — Contact us to confirm |
| Corrosion Resistance |
Good — suitable for outdoor and humid environments; not recommended for marine/chloride-heavy use |
| Country of Origin |
Contact us to confirm |
⚠️ Note: For marine, saltwater, or high-chloride environments, A4 (316) stainless steel is generally recommended over A2 (304). Contact us if you need A4-grade alternatives.
❓ Frequently Asked Questions
How do I choose the right length for a countersunk machine screw?
A general guideline is to select a length equal to the thickness of the material being fastened plus at least one screw diameter of thread engagement in the receiving part. For example, fastening a 1/4” panel with a #8-32 screw typically calls for a 3/8” or 1/2” length. Available lengths in this listing range from 3/16” to 1-1/2” depending on the diameter selected.
What does A2 stainless steel mean, and how strong is it?
A2 stainless steel (also known as 304 stainless) is an austenitic grade with good corrosion resistance and a tensile strength typically around 500–700 MPa depending on the specific production standard (commonly A2-70). It is non-magnetic in its annealed state and well suited for general-purpose indoor and outdoor fastening where rust resistance is required.
Can A2 stainless screws be used outdoors or in wet environments?
Yes. A2 stainless steel provides significantly better corrosion resistance than zinc-plated carbon steel and is generally suitable for outdoor, humid, and mildly corrosive environments. For marine or chloride-heavy environments, A4 (316) stainless is typically recommended instead. Contact us if you need A4-grade options.
What thread standard do these screws use?
These screws use the Unified National Coarse (UNC) thread standard, which is the most common inch-based thread system in the United States. Available sizes are #4-40, #6-32, #8-32, #10-24, and 1/4-20 — all compatible with standard UNC nuts, threaded inserts, and tapped holes per ASME B1.1.
What driver bit do I need for these Phillips countersunk screws?
A Phillips PH1 bit is typically used for #4 and #6 screws. A PH2 bit is generally appropriate for #8, #10, and 1/4-20. Always match the bit size to the screw head to minimize cam-out, especially when using a power driver at higher torque settings.
How do I choose between #4-40, #6-32, #8-32, #10-24, and 1/4-20?
Choose based on the load, the clearance hole size, and the tapped hole or nut in your assembly. #4-40 and #6-32 are commonly used in electronics, small enclosures, and light fixtures. #8-32 and #10-24 suit general mechanical assemblies and appliance hardware. 1/4-20 is preferred for heavier structural connections and equipment mounting.
What is a countersunk flat head screw used for?
A countersunk (flat head) screw is designed to sit flush with or below the surface of the material when installed in a pre-drilled countersunk hole. This makes it ideal for applications where a smooth, snag-free surface is required — such as electronics enclosures, cabinetry, panel mounting, and structural brackets where a protruding head would interfere with assembly or aesthetics.
🛒 Select your size and quantity above, then add to cart — ships from our US warehouse.
