{"product_id":"a2-stainless-phillips-countersunk-screws-4-40-1-4-20","title":"A2 Stainless Steel Phillips Flat Head Machine Screws | UNC #4-40 to 1\/4-20","description":"\u003cp\u003e \u003c\/p\u003e\n\u003cdiv class=\"hdiy-desc\"\u003e\n\u003cdiv class=\"hdiy-overview\"\u003e\n\u003ch2\u003eA2 Stainless Steel Phillips Countersunk Machine Screws — Rust-Resistant, Flush-Mount, UNC Thread\u003c\/h2\u003e\n\u003cp\u003eZinc-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 \u003cstrong\u003eA2 stainless steel Phillips countersunk machine screws\u003c\/strong\u003e 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.\u003c\/p\u003e\n\u003cp\u003eEach 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.\u003c\/p\u003e\n\u003cp\u003eThese \u003cstrong\u003estainless flat head machine screws\u003c\/strong\u003e 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 \u003cstrong\u003eUNC stainless machine screws\u003c\/strong\u003e are the specified fastener.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-compat\"\u003e\n\u003cspan class=\"hdiy-compat-icon\"\u003e🔩\u003c\/span\u003e \u003cstrong\u003eThread Standard:\u003c\/strong\u003e 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.\u003c\/div\u003e\n\u003ch2\u003e✅ Key Features of These A2 Stainless Phillips Countersunk Machine Screws\u003c\/h2\u003e\n\u003cul class=\"hdiy-features\"\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e🥊\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eA2 Stainless Steel (304 Grade)\u003c\/strong\u003e — Provides substantially better corrosion resistance than zinc-plated carbon steel, making these \u003cem\u003estainless flat head machine screws\u003c\/em\u003e suitable for outdoor, humid, and mildly corrosive environments.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e⬇️\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eFlush-Mount Countersunk Head\u003c\/strong\u003e — 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.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e✚️\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003ePhillips Cross Drive\u003c\/strong\u003e — 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.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e📐\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eFive UNC Sizes in One Listing\u003c\/strong\u003e — #4-40 through 1\/4-20 covers the most common \u003cem\u003eUNC machine screw\u003c\/em\u003e sizes used in US electronics, appliances, and mechanical assemblies, reducing the number of separate SKUs to manage.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e📦\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eBulk Packs of 50 or 100 Pieces\u003c\/strong\u003e — Sized for production runs, workshop restocking, and repair kits; larger packs reduce per-unit cost for repeat \u003cem\u003estainless countersunk screw\u003c\/em\u003e applications.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e⚙️\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eASME B1.1 UNC Thread Compatibility\u003c\/strong\u003e — 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.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003e📐 Technical Specifications — A2 Stainless Phillips Flat Head Machine Screws\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-table-wrap\"\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eProduct Type\u003c\/th\u003e\n\u003ctd\u003ePhillips Countersunk (Flat Head) Machine Screw\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eDrive Type\u003c\/th\u003e\n\u003ctd\u003ePhillips (Cross) — PH1 \/ PH2\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHead Style\u003c\/th\u003e\n\u003ctd\u003eCountersunk \/ Flat Head (flush-mount)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHead Angle\u003c\/th\u003e\n\u003ctd\u003e82° (UNC inch standard)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003eA2 Stainless Steel (304 Grade)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eThread Standard\u003c\/th\u003e\n\u003ctd\u003eUNC — Unified National Coarse (ASME B1.1)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eAvailable Sizes\u003c\/th\u003e\n\u003ctd\u003e#4-40, #6-32, #8-32, #10-24, 1\/4-20\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eThread Pitch\u003c\/th\u003e\n\u003ctd\u003e#4-40: 40 TPI | #6-32: 32 TPI | #8-32: 32 TPI | #10-24: 24 TPI | 1\/4-20: 20 TPI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eAvailable Lengths\u003c\/th\u003e\n\u003ctd\u003e3\/16” to 1-1\/2” — See variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003ePacking Quantity\u003c\/th\u003e\n\u003ctd\u003e#4-40: 100 pcs | #6 through 1\/4-20: 50 pcs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eTensile Strength\u003c\/th\u003e\n\u003ctd\u003eTypically 500–700 MPa (A2-70 grade) — Contact us to confirm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCorrosion Resistance\u003c\/th\u003e\n\u003ctd\u003eGood — suitable for outdoor and humid environments; not recommended for marine\/chloride-heavy use\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCountry of Origin\u003c\/th\u003e\n\u003ctd\u003eContact us to confirm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-note\"\u003e\n\u003cspan class=\"hdiy-note-icon\"\u003e⚠️\u003c\/span\u003e \u003cstrong\u003eNote:\u003c\/strong\u003e 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.\u003c\/div\u003e\n\u003ch2\u003e❓ Frequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-faq\"\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow do I choose the right length for a countersunk machine screw?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat does A2 stainless steel mean, and how strong is it?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA2 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan A2 stainless screws be used outdoors or in wet environments?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eYes. 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat thread standard do these screws use?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eThese 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat driver bit do I need for these Phillips countersunk screws?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow do I choose between #4-40, #6-32, #8-32, #10-24, and 1\/4-20?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eChoose 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is a countersunk flat head screw used for?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-cta\"\u003e🛒 Select your size and quantity above, then add to cart — ships from our US warehouse.\u003c\/div\u003e\n\u003c\/div\u003e","brand":"HomeDIYer","offers":[{"title":"4#-40*3\/16 \/ 100pcs","offer_id":52285158097170,"sku":"LFL2024TENGLUOWJ24593x100","price":13.57,"currency_code":"USD","in_stock":true},{"title":"4#-40*1\/4 \/ 100pcs","offer_id":52285158129938,"sku":"LFL2024TENGLUOWJ24594x100","price":13.74,"currency_code":"USD","in_stock":true},{"title":"4#-40*5\/16 \/ 100pcs","offer_id":52285158162706,"sku":"LFL2024TENGLUOWJ24595x100","price":15.1,"currency_code":"USD","in_stock":true},{"title":"4#-40*3\/8 \/ 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