{"product_id":"heli-coil-3591-7cnw438-7-16-20-unf-locking-insert-304-ss","title":"Heli-coil 3591-7CNW438 7\/16-20 Unf Locking Insert 304 Ss","description":"\u003ch3\u003eProduct Description\u003c\/h3\u003e\n\u003cp\u003eThe HELI-COIL 3591-7CNW438 is a tangless screw-locking helical coil insert designed to create or restore strong, vibration-resistant threaded connections in a host material. Manufactured from Grade 304 stainless steel with a dry film lubricant finish, it accepts a 7\/16-20 UNF fastener thread and provides a 1D length-to-diameter ratio with an overall installed length of 0.438 inches. The locking function is built into the insert coil itself, eliminating the need for separate locking hardware. Maximum locking torque is rated at 100 inch-pounds, and minimum break-away torque is 14 inch-pounds. Machinists, maintenance technicians, and MRO professionals install these inserts to reinforce tapped holes in aluminum, cast iron, and similar host materials.\u003c\/p\u003e\n\u003cp\u003eThis insert is suited for aerospace, automotive, industrial, and general mechanical applications where thread integrity under vibration or repeated assembly cycles is required. The tangless design eliminates the installation and removal steps associated with tanged inserts, reducing assembly time and the risk of tang debris in the host bore. The dry film lubricant coating aids consistent torque control during fastener installation. Single-insert packaging supports repair and low-volume production use; minimum order quantity is 25 pieces.\u003c\/p\u003e\n\u003ch4\u003eKey Features\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e7\/16-20 UNF thread size with 1D length-to-diameter ratio and 0.438-inch overall length\u003c\/li\u003e\n  \u003cli\u003eGrade 304 stainless steel construction for corrosion resistance in demanding environments\u003c\/li\u003e\n  \u003cli\u003eTangless design eliminates tang break-off steps and reduces debris risk in blind holes\u003c\/li\u003e\n  \u003cli\u003eDry film lubricant finish supports consistent installation torque and reduces galling\u003c\/li\u003e\n  \u003cli\u003eMaximum locking torque of 100 inch-pounds with minimum break-away torque of 14 inch-pounds\u003c\/li\u003e\n  \u003cli\u003e6-5\/8 free coils; outside diameter range of 0.524 to 0.549 inches for proper host hole fit\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003eCompatibility\u003c\/h4\u003e\n\u003cp\u003eDesigned as a screw-locking replacement or thread-repair insert for tapped holes requiring a 7\/16-20 UNF internal thread with a 1D insert length. Verify host material tap size per HELI-COIL installation specifications before use.\u003c\/p\u003e\n\u003ch4\u003eInstallation Notes\u003c\/h4\u003e\n\u003cp\u003eInstallation requires a HELI-COIL-specified tap to prepare the host hole to the correct oversize diameter before insert placement. A compatible tangless installation tool should be used to drive and seat the insert without damaging the coil or host material. Power down or de-energize any assembly before performing thread repair on in-service components. Refer to applicable torque specifications for the fastener being used after insert installation is complete.\u003c\/p\u003e\n\u003ch4\u003eTechnical Specifications\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThread Size\u003c\/strong\u003e: 7\/16-20 UNF\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThread Standard\u003c\/strong\u003e: UNF\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLength to Diameter Ratio\u003c\/strong\u003e: 1D\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOverall Insert Length\u003c\/strong\u003e: 0.438 inches\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMinimum Outside Diameter\u003c\/strong\u003e: 0.524 inches\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Outside Diameter\u003c\/strong\u003e: 0.549 inches\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaximum Locking Torque\u003c\/strong\u003e: 100 inch-pounds\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMinimum Break-Away Torque\u003c\/strong\u003e: 14 inch-pounds\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNumber of Free Coils\u003c\/strong\u003e: 6-5\/8\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTang\u003c\/strong\u003e: Tangless\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial\u003c\/strong\u003e: Stainless Steel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial Grade\u003c\/strong\u003e: 304\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCoating\/Finish\u003c\/strong\u003e: Dry Film Lubricant\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWeight\u003c\/strong\u003e: 0.07 pounds\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003eStandard Information\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBrand\u003c\/strong\u003e: HELI-COIL\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer Part Number\u003c\/strong\u003e: 3591-7CNW438\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"HELI-COIL","offers":[{"title":"Default Title","offer_id":52065145454898,"sku":"3591-7CNW438","price":60.65,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0270\/4519\/9983\/files\/a15767eeef787456465cbe578af3d9c4_3769e13f-2318-4127-9675-0704d7033387.jpg?v=1790044593","url":"https:\/\/voomisupply.com\/products\/heli-coil-3591-7cnw438-7-16-20-unf-locking-insert-304-ss","provider":"Voomi Supply","version":"1.0","type":"link"}