{"product_id":"grade-12-9-hex-socket-cap-screw","title":"Grade 12.9 Hex Socket Cap Screw","description":"\u003cp\u003e\u003cstrong\u003eMetric hex socket cap screws, property class 12.9, supplied to your size and quantity.\u003c\/strong\u003e The standard fastener for mold plate stacks, where a small head has to develop a lot of clamp force in a counterbore. Send the sizes and quantities, or a BOM, and we quote in writing, normally within one business day.\u003c\/p\u003e\u003ch2\u003eWhat property class 12.9 actually means\u003c\/h2\u003e\u003cp\u003eThe two numbers are a specification, not a grade name. The first (12) is the nominal tensile strength in hundreds of MPa — 1200 MPa. The second (9) is the ratio of yield to tensile, 0.9, so yield is about 1080 MPa. That is roughly twice the strength of a common 8.8 screw of the same size, which is why mold plates can be held by screws that fit in a modest counterbore.\u003c\/p\u003e\u003cp\u003eThe trade-off is worth knowing: \u003cstrong\u003ehigher strength classes are less ductile and more notch-sensitive.\u003c\/strong\u003e A 12.9 screw tolerates less abuse than an 8.8 — a damaged thread, a burr under the head, or a socket rounded out by the wrong key are all more likely to end in a broken screw rather than a stripped one. And a screw broken flush in a mold plate is an expensive afternoon.\u003c\/p\u003e\u003ch2\u003eThe three things that break these in practice\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSeating on a burr or a chip.\u003c\/strong\u003e The head must bear on a clean, flat, square counterbore. A chip under the head means the preload you think you applied is not there, and the joint moves — then the screw fatigues.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe wrong hex key.\u003c\/strong\u003e An imperial key in a metric socket, or a worn key, rounds the socket. On 12.9 the socket walls are hard and will chip rather than deform.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReusing screws that have been fully tightened many times.\u003c\/strong\u003e These are usually torqued into the elastic range and can be reused, but a screw that has been overtightened has yielded and will not develop the same preload again. If a joint keeps loosening, replace the screws before re-torquing them again.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eFinish, and where it matters\u003c\/h2\u003e\u003cp\u003eBlack oxide is the normal supply condition and offers modest corrosion resistance. Zinc plating is available, but be aware that plating processes can introduce hydrogen embrittlement risk in high-strength fasteners unless properly baked — if you need plated 12.9 screws, tell us and we will confirm the process and the baking treatment in writing rather than assuming it.\u003c\/p\u003e\u003ch2\u003eWhat to send us\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eThread size and pitch, and whether it is coarse or fine\u003c\/li\u003e\n\u003cli\u003eUnder-head length and thread length\u003c\/li\u003e\n\u003cli\u003eHead diameter, head height and socket size, or the standard you work to (DIN 912 \/ ISO 4762 and similar)\u003c\/li\u003e\n\u003cli\u003eFinish required, and whether plating with baking is needed\u003c\/li\u003e\n\u003cli\u003eCertificates required — material, mechanical properties, or a batch certificate\u003c\/li\u003e\n\u003cli\u003eQuantity per size, packaging, and destination\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSending a mixed BOM for mold maintenance is fine — several sizes and small quantities in one quotation is normal for us.\u003c\/p\u003e\u003ch2\u003eDocumentation and confidentiality\u003c\/h2\u003e\u003cp\u003eProperty class 12.9 is confirmed in the formal quotation together with the dimensional standard, coating and certificate availability — it is not assumed from a product title. Technical files are used to evaluate and fulfill your inquiry or order. They may be shared only with relevant manufacturing, inspection, logistics or service partners as needed. Send only files you are authorized to share. See our \u003ca href=\"\/pages\/privacy-policy\"\u003ePrivacy Policy\u003c\/a\u003e. NDA on request from \u003ca href=\"mailto:rfq@privleymold.com\"\u003erfq@privleymold.com\u003c\/a\u003e.\u003c\/p\u003e","brand":"Privley Mold Components","offers":[{"title":"Default Title","offer_id":52126011359452,"sku":"PMC-SCR-129-SHCS","price":0.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0846\/7650\/9916\/files\/privley-hex-socket-cap-screw-rfq-diagram_6c8ac403-f81e-41e7-944b-37ce8d6def69.png?v=1785388366","url":"https:\/\/privleymold.com\/products\/grade-12-9-hex-socket-cap-screw","provider":"Privley Mold Components","version":"1.0","type":"link"}