MF Supply is a leading supplier of Heavy Duty & Thickwall Keensert® style key-locking inserts (MS51831 & NAS1395) in inch & Mil-Spec sizes, including major brands and equivalents to Acme, Alcoa, Camloc, Clarendon, Fairchild, Kaynar, Microdot, Tridair Keenserts®, Chrislynn, McMaster-Carr, Carr-Lane, Jergens, Howmet & Keyserts. Where applicable, our products are DFAR compliant with COC and full certifications available upon request. Keensert® Style Key-Locking Inserts Heavy Duty, Thickwall, MS51831 & NAS1395 Materials AvailableOur Keenserts® style key-locking inserts catalog of Heavy Duty & Thickwall series includes MS51831, NAS1395, MS51831CA, NAS1395CA, MS51831A, NAS1395A, KNH, KNHL, KNH-F, KNH-T, and KNH-MX. They come in Locking and Non-Locking styles and are available in various inch/imperial & Mil-Spec sizes, and in the materials outlined below. KNH, KNHL, MS51831, and NAS1395 Series – Stainless SteelThe KNHM, KNHML, MS51831, and NAS1395 series Heavy Duty & Thickwall Keensert® style key-locking inserts, made from high-grade 303 stainless steel, are designed to deliver exceptional corrosion resistance and mechanical reliability in demanding environments. Engineered for use in marine, aerospace, and high-humidity industrial applications, these threaded inserts maintain thread integrity under exposure to moisture, salt spray, and corrosive agents. Their high tensile strength and resistance to thread wear make them a preferred choice for structural fastening in environments where component longevity and joint stability are critical. They are available in inch and Mil-Spec thread sizes ranging from 4-40 to 1-12.
KNH-F Series – Carbon SteelThe KNH-F series Heavy Duty & Thickwall Keensert® style key-locking inserts, made from carbon steel (also known as black-phosphate steel), delivers exceptional mechanical strength and cost efficiency for high-load industrial applications. The carbon steel composition provides a high tensile strength-to-cost ratio, ideal for applications in construction, automotive, and heavy machinery sectors requiring robust fastening solutions. Designed to withstand significant shear and torque forces, these key-locking inserts ensure thread integrity under dynamic stress. They are available in inch and Mil-Spec thread sizes ranging from 8-32 to 1-1/2-16.
KNH-T, MS51831CA, and NAS1395CA Series – A286 Stainless SteelThe KNH-T, MS51831CA and NAS1395CA series Heavy Duty & Thickwall Keensert® style key-locking inserts, manufactured from A286 stainless steel, are optimized for high-temperature and corrosive environments. A286’s precipitation-hardened alloy composition provides elevated yield strength (up to 130 ksi) and thermal stability (up to 1300°F), making it critical for aerospace and defense applications such as turbine engines and exhaust systems. These inserts ensure secure, vibration-resistant threading in environments where thermal and mechanical loads exceed the capabilities of standard stainless steel. They are offered in inch and Mil-Spec thread sizes ranging from 8-32 to 1-12.
KNH-MX, MS51831A, and NAS1395A Series – 4140 Alloy SteelThe KNH-MX, MS51831A, and NAS1395A series Heavy Duty & Thickwall Keensert® style key-locking inserts, crafted from 4140 alloy steel, are engineered for maximum durability and load-bearing capacity in high-stress applications. The 4140 alloy, with a tensile strength of approximately 140 ksi and enhanced fatigue resistance, is ideal for heavy machinery, aerospace components, and industrial equipment subjected to continuous mechanical stress. These inserts provide great thread strength and impact resistance, ensuring long-term reliability. They are available in inch and Mil-Spec thread sizes from 8-32 to 1-12.
KNH & KNHL Series – Nitronic 60The KNH and KNHL series Heavy Duty & Thickwall Keensert® style key-locking inserts, forged from Nitronic 60 stainless steel, are designed for exceptional galling resistance, wear endurance, and corrosion protection in harsh industrial environments. Nitronic 60’s high yield strength and resistance to chloride pitting make it ideal for chemical processing, marine, and petrochemical applications. These inserts maintain thread integrity under abrasive conditions and high-friction interfaces, enhancing component longevity. They are available in inch and Mil-Spec thread sizes ranging from 8-32 to 1-12.
Cross-reference tables' links: Resources: Why Buy Heavy Duty & Thickwall Keensert® Style Key-Locking Inserts (MS51831 & NAS1395) from MF Supply?With over 50 years of experience as a supply chain partner to manufacturers, and deep and broad expertise in inch & Mil-Spec fasteners and inserts, MF Supply can help with all your fastening and hardware needs.
We stock a huge inventory of Keensert® style key-locking inserts Heavy Duty & Thickwall, MS51831 & NAS1395 series in inch/imperial and Mil-Spec sizes. Standard materials offered include 303 Stainless Steel, A286, Nitronic 60, 4140 Alloy and Carbon Steel (Black-Phosphate Steel). Standard sizes run from 4-40 through 1-1/2-12.
Additional Inch & Mil-Spec key-locking insert product lines include Miniature & Thinwall, Solid, Extra Heavy Duty, installation tools and kits. Special materials and nonstandard sizes may be available for special orders with a lead time. Can't find what you're looking for? Email us at [email protected] for a custom quote. "We have the right screw for you" is our motto after all!
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