{"product_id":"m8-carriage-bolts-a2-70-stainless-steel-coach-screws","title":"M8 Carriage Bolts A2-70 Stainless Steel | Round Head Square Neck Coach Screws","description":"\u003cp\u003e \u003c\/p\u003e\n\u003cdiv class=\"hdiy-desc\"\u003e\n\u003c!-- ① OVERVIEW --\u003e\n\u003cdiv class=\"hdiy-overview\"\u003e\n\u003ch2\u003eM8 Carriage Bolts in A2-70 Stainless Steel — Reliable, Corrosion-Resistant Fastening for Heavy-Duty Wood Projects\u003c\/h2\u003e\n\u003cp\u003eWhen standard zinc-plated bolts rust out after a single season or strip under load, the whole joint fails — and so does your project. These M8 carriage bolts in A2-70 stainless steel are built for DIYers, woodworkers, and contractors who need a heavier-duty, corrosion-resistant fastener for timber framing, deck construction, and outdoor structural connections.\u003c\/p\u003e\n\u003cp\u003eEach box contains M8 round head square neck coach screws in your chosen bolt length and pack quantity. The M8 thread diameter (8mm \/ ≈5\/16\") follows the ISO metric coarse standard with a 1.25mm pitch. Bolt lengths range from 30mm (≈1-3\/16\") to 70mm (≈2-3\/4\"), and packs are available in 15, 20, 25, or 30 pieces per labeled storage box — sized to match everything from a quick repair to a full framing run.\u003c\/p\u003e\n\u003cp\u003eTypical applications include heavy timber deck framing where M8 stainless carriage bolts provide the clamping force needed across thick lumber, pergola and arbor assembly where weather resistance is non-negotiable, and fence post rail connections where the self-locking square neck eliminates bolt spin during single-handed tightening.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c!-- ② COMPATIBILITY BAR --\u003e\n\u003cdiv class=\"hdiy-compat\"\u003e\n\u003cspan class=\"hdiy-compat-icon\"\u003e🔩\u003c\/span\u003e \u003cstrong\u003eCompatibility:\u003c\/strong\u003e Fits standard M8 hex nuts, M8 nylon lock nuts, and M8 flat or spring washers (ISO metric). Thread pitch: 1.25mm coarse. Square neck seats into wood, plywood, and soft composites.\u003c\/div\u003e\n\u003c!-- ③ KEY FEATURES --\u003e\n\u003ch2\u003e✅ Key Features of These M8 Stainless Steel Carriage Bolts\u003c\/h2\u003e\n\u003cul class=\"hdiy-features\"\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e🛡️\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eA2-70 Stainless Steel Construction\u003c\/strong\u003e — Meets ISO 3506 A2-70 with a minimum tensile strength of 700 MPa, delivering dependable clamping force for structural timber joints and heavy outdoor assemblies.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e🌧️\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eRust-Resistant for Year-Round Outdoor Use\u003c\/strong\u003e — Austenitic A2 stainless resists oxidation, staining, and corrosion in rain, humidity, and mild coastal conditions — ideal for deck framing bolts and garden structure hardware.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e🔒\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eSelf-Locking Square Neck Design\u003c\/strong\u003e — The square shoulder bites into wood grain as the nut is tightened, preventing bolt spin and enabling one-person installation without a backup wrench on the head.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e📏\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eFive Length Options (30mm–70mm)\u003c\/strong\u003e — Choose from 30mm (≈1-3\/16\"), 40mm (≈1-9\/16\"), 50mm (≈2\"), 60mm (≈2-3\/8\"), or 70mm (≈2-3\/4\") to match your exact material stack thickness without cutting or shimming.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e📦\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eOrganized Storage Box Included\u003c\/strong\u003e — Each pack ships in a labeled box (15, 20, 25, or 30 pcs) so fasteners stay sorted on the job site and unused bolts are easy to store for future repairs or follow-on phases.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"hdiy-icon\"\u003e📏\u003c\/span\u003e \u003cspan\u003e\u003cstrong\u003eCompatible with Pressure-Treated Lumber\u003c\/strong\u003e — A2 stainless resists the corrosive chemistry of ACQ and CA treated wood, making these M8 coach screws a code-friendly choice for residential deck and fence construction.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- ④ TECHNICAL SPECIFICATIONS --\u003e\n\u003ch2\u003e📐 Technical Specifications — M8 Round Head Square Neck Carriage Bolts\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-table-wrap\"\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eThread Diameter\u003c\/th\u003e\n\u003ctd\u003eM8 (8mm \/ ≈5\/16\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eThread Standard\u003c\/th\u003e\n\u003ctd\u003eISO Metric Coarse, Pitch 1.25mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eAvailable Bolt Lengths\u003c\/th\u003e\n\u003ctd\u003e30mm (≈1-3\/16\"), 40mm (≈1-9\/16\"), 50mm (≈2\"), 60mm (≈2-3\/8\"), 70mm (≈2-3\/4\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHead Type\u003c\/th\u003e\n\u003ctd\u003eRound Head (Dome) with Square Neck\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eDrive Type\u003c\/th\u003e\n\u003ctd\u003eNut-driven (no drive recess on head)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003eA2 Austenitic Stainless Steel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eStrength Grade\u003c\/th\u003e\n\u003ctd\u003eA2-70 (Min. tensile strength 700 MPa)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eStandard\u003c\/th\u003e\n\u003ctd\u003eISO 3506 \/ DIN 603\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCompatible Nut\u003c\/th\u003e\n\u003ctd\u003eM8 Hex Nut, M8 Nylon Lock Nut\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCompatible Washer\u003c\/th\u003e\n\u003ctd\u003eM8 Flat Washer, M8 Spring Washer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003ePack Quantity Options\u003c\/th\u003e\n\u003ctd\u003e15 pcs, 20 pcs, 25 pcs, 30 pcs (per box)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eFinish\u003c\/th\u003e\n\u003ctd\u003eMill finish stainless (no coating)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHead Diameter\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eSquare Neck Size\u003c\/th\u003e\n\u003ctd\u003eSee variant options\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\u003c!-- ⑤ FAQ --\u003e\n\u003ch2\u003e❓ Frequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-faq\"\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eHow do I choose the right M8 bolt length for my project?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA general rule is to select a bolt length equal to the combined thickness of all materials being joined, plus enough thread to fully engage the nut — typically 1–2 thread pitches beyond the nut face. For example, connecting two 20mm boards generally calls for a 50mm (≈2\") bolt when using a washer and nut. Available lengths run from 30mm (≈1-3\/16\") to 70mm (≈2-3\/4\").\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eWhat tensile strength does A2-70 stainless steel provide for M8 bolts?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eA2-70 per ISO 3506 specifies a minimum tensile strength of 700 MPa (≈101,500 psi). For M8 bolts, this translates to a proof load generally in the range of 16–18 kN, making them suitable for structural wood joints, outdoor furniture, and light-to-medium load-bearing connections. For critical structural steel applications, consult an engineer for load calculations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eAre these M8 carriage bolts suitable for outdoor or coastal environments?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eYes. A2 austenitic stainless steel resists rust, oxidation, and staining in most outdoor conditions including rain, humidity, and mild coastal exposure. For direct saltwater immersion or highly aggressive marine environments, A4 (316) stainless is typically the recommended upgrade. These bolts are well-suited for decks, pergolas, fences, and garden structures in standard outdoor conditions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eWhat thread standard do these M8 bolts use, and what nuts are compatible?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eThese bolts use the M8 metric coarse thread (ISO 68-1) with a standard pitch of 1.25mm. They are compatible with standard M8 hex nuts, M8 nylon insert lock nuts (Nyloc), and M8 flat or spring washers. They are \u003cem\u003enot\u003c\/em\u003e compatible with UNC\/UNF inch-standard hardware.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eWhy does a carriage bolt have a square neck instead of a hex head?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eThe square shoulder under the round dome head is designed to embed into wood or soft composite as the nut is tightened, preventing the bolt from spinning. This allows single-person installation — you tighten the nut from one side without needing to hold the bolt head with a second tool. It also leaves a smooth, snag-free dome on the visible face of the joint.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eWhich pack size should I order for my project?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eFor small repairs or single-use projects, a 15-piece box is generally sufficient. For deck framing, pergola construction, or fence post connections, the 25- or 30-piece boxes offer better value per bolt. All packs ship in a labeled storage box to keep fasteners organized on the job site and easy to store for future use.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails open=\"\"\u003e\n\u003csummary\u003eCan I use M8 stainless carriage bolts with pressure-treated lumber?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eYes. A2 stainless steel is generally compatible with ACQ (Alkaline Copper Quaternary) and CA (Copper Azole) pressure-treated lumber, which can rapidly corrode standard zinc-plated or hot-dip galvanized fasteners over time. Stainless steel fasteners are typically the recommended choice for treated wood in residential deck and fence construction per IRC guidelines.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003c!-- ⑥ CTA BAR --\u003e\n\u003cdiv class=\"hdiy-cta\"\u003e🛒 Select your \u003cstrong\u003ebolt length and pack quantity\u003c\/strong\u003e above, then add to cart — ships from our US warehouse.\u003c\/div\u003e\n\u003c\/div\u003e","brand":"HomeDIYer","offers":[{"title":"M8 \u0026 8mm \/ 30mm \/ 30PCS\u0026BOX","offer_id":52308509425938,"sku":"KAYFST029-8","price":12.58,"currency_code":"USD","in_stock":true},{"title":"M8 \u0026 8mm \/ 40mm \/ 25PCS\u0026BOX","offer_id":52308509458706,"sku":"KAYFST029-9","price":12.69,"currency_code":"USD","in_stock":true},{"title":"M8 \u0026 8mm \/ 50mm \/ 20PCS\u0026BOX","offer_id":52308509491474,"sku":"KAYFST029-10","price":11.76,"currency_code":"USD","in_stock":true},{"title":"M8 \u0026 8mm \/ 60mm \/ 20PCS\u0026BOX","offer_id":52308509524242,"sku":"KAYFST029-11","price":13.33,"currency_code":"USD","in_stock":true},{"title":"M8 \u0026 8mm \/ 70mm \/ 15PCS\u0026BOX","offer_id":52308509557010,"sku":"KAYFST029-12","price":12.72,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0884\/8936\/1682\/files\/P_009_514f56d5-13f2-460a-8bd5-c06ca02d65fd.jpg?v=1780502211","url":"https:\/\/homediyer.com\/de\/products\/m8-carriage-bolts-a2-70-stainless-steel-coach-screws","provider":"HomeDIYer","version":"1.0","type":"link"}