{"product_id":"4-jaw-self-centering-chuck","title":"4 Jaw Self Centering Chuck for Metal Lathe — 3\", 4\", 5\"","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThe Autobox K12 series 4 jaw self centering chuck mounts to your lathe's headstock spindle nose and grips round or square stock using all four jaws simultaneously. Unlike a 4-jaw independent chuck — where each jaw is adjusted separately — the K12 self-centering scroll mechanism moves all four jaws in unison with a single wrench, delivering quick, repeatable centering without dial-indicator setup. Available in 3-inch (80 mm), 4-inch (100 mm), and 5-inch (125 mm) diameters to suit mini lathes through medium bench lathes.\u003c\/p\u003e\n\u003ch2\u003eAvailable Options\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e3 inch (80 mm)\u003c\/strong\u003e — K12-80 — $64.95 — suited to 7x10 and 7x12 mini lathes; compact footprint for small-bore turning\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e4 inch (100 mm)\u003c\/strong\u003e — K12-100 — $79.95 — most popular size for 7x14 and 8x16 mini lathes; balanced capacity and rigidity\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e5 inch (125 mm)\u003c\/strong\u003e — K12-125 — $94.95 — for medium bench lathes; larger through-bore capacity for longer stock\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSimultaneous 4-jaw scroll drive:\u003c\/strong\u003e one bevel pinion turns the scroll, moving all four jaws together — faster setup than a 4-jaw independent chuck\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eK12 series construction:\u003c\/strong\u003e hardened scroll plate and jaw serrations; body material matched to K12 industry standard for chuck runout ≤0.05 mm (0.002\")\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReversible jaws:\u003c\/strong\u003e internal jaws for gripping shaft OD; flip to external jaw configuration for larger-diameter OD or face-plate work\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFour-jaw grip on square stock:\u003c\/strong\u003e four contact points give more secure grip on square bar than a 3-jaw, with less risk of jaw marks on round stock than an independent chuck\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eChuck key included:\u003c\/strong\u003e T-handle bevel-drive chuck wrench included with each size; fits all four pinion sockets\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree sizes, one product page:\u003c\/strong\u003e select 3\", 4\", or 5\" diameter from the variant dropdown — same K12 mechanism, scaled to your machine\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eSpec\u003c\/th\u003e\n\u003cth\u003e3 inch (K12-80)\u003c\/th\u003e\n\u003cth\u003e4 inch (K12-100)\u003c\/th\u003e\n\u003cth\u003e5 inch (K12-125)\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChuck diameter\u003c\/td\u003e\n\u003ctd\u003e80 mm (3.15\")\u003c\/td\u003e\n\u003ctd\u003e100 mm (3.94\")\u003c\/td\u003e\n\u003ctd\u003e125 mm (4.92\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSKU\u003c\/td\u003e\n\u003ctd\u003eK12-80\u003c\/td\u003e\n\u003ctd\u003eK12-100\u003c\/td\u003e\n\u003ctd\u003eK12-125\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNumber of jaws\u003c\/td\u003e\n\u003ctd\u003e4\u003c\/td\u003e\n\u003ctd\u003e4\u003c\/td\u003e\n\u003ctd\u003e4\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eJaw type\u003c\/td\u003e\n\u003ctd colspan=\"3\"\u003eReversible — internal and external configuration\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDrive mechanism\u003c\/td\u003e\n\u003ctd colspan=\"3\"\u003eScroll plate (self-centering) — all 4 jaws move simultaneously\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRunout (TIR)\u003c\/td\u003e\n\u003ctd colspan=\"3\"\u003e≤0.05 mm (≤0.002\") at jaw faces\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMounting method\u003c\/td\u003e\n\u003ctd colspan=\"3\"\u003eBolt-on to spindle nose via back plate (back plate sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChuck wrench included\u003c\/td\u003e\n\u003ctd colspan=\"3\"\u003eYes — T-handle bevel-drive wrench\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch2\u003eCompatibility\u003c\/h2\u003e\n\u003cp\u003eThis chuck mounts to the lathe headstock spindle nose via a bolt-on back plate. \u003cstrong\u003eA matching adapter back plate is required and sold separately\u003c\/strong\u003e — the chuck does not mount directly into the MT3 headstock taper. Select a back plate matched to your specific spindle nose thread and register diameter.\u003c\/p\u003e\n\u003cp\u003eCompatible lathe models (with appropriate adapter back plate):\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eSieg C2 \/ SC2 \/ C3 mini lathes (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eHarbor Freight 7x10 #93212 and 7x12 #44142 (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eGrizzly G0602, G0765 (7x14), and G8688 (7x12) (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eLittleMachineShop HiTorque 7x16 (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eAutobox 7x14 and 8x16 mini lathes (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eSouth Bend 9\" lathe (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eJet BD-X series bench lathes (MT3 headstock)\u003c\/li\u003e\n\u003cli\u003eAtlas \/ Craftsman 12\"x36\" (MT3 headstock)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eNot sure if your lathe's spindle nose matches? Message us with your lathe model — we'll confirm the correct back plate before you order.\u003c\/p\u003e\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1 × K12 series 4-jaw self-centering chuck (size as selected)\u003c\/li\u003e\n\u003cli\u003e1 × T-handle chuck wrench (fits all 4 pinion sockets)\u003c\/li\u003e\n\u003cli\u003e1 × Set of jaw mounting hardware\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eNote: Adapter back plate is NOT included. A back plate matched to your spindle nose thread and register is required for installation.\u003c\/em\u003e\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What is the difference between a 4-jaw self-centering chuck and a 4-jaw independent chuck?\u003c\/strong\u003e\u003cbr\u003eA: In a self-centering chuck (this K12 series), all four jaws move simultaneously through a single scroll gear — turn any of the four bevel pinion sockets and all jaws tighten or open together. This centers round or square stock automatically and quickly. In a 4-jaw independent chuck (our K72 series, sold separately), each jaw is adjusted individually using its own screw. Independent chucks allow precise off-center or eccentric workholding and can grip irregular shapes, but require a dial indicator and more setup time. If you mostly turn round or square bar and want fast centering, choose this self-centering K12. If you need off-center or irregular workholding, choose the K72 independent chuck.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"Autobox","offers":[{"title":"3 inch","offer_id":46727462420617,"sku":"K12-80","price":64.95,"currency_code":"USD","in_stock":true},{"title":"4 inch","offer_id":46727462453385,"sku":"K12-100","price":79.95,"currency_code":"USD","in_stock":true},{"title":"5 inch","offer_id":46727462486153,"sku":"K12-125","price":94.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0762\/4923\/5593\/files\/4_Jaw_Self_Centering_Chuck_Jaw_Key.webp?v=1778731625","url":"https:\/\/autoboxtoolworks.com\/products\/4-jaw-self-centering-chuck","provider":"AutoBoxToolWorks","version":"1.0","type":"link"}