Top 17 Keensert® Questions: Expert Answers to Common Questions (Part 2)
Posted: April 28, 2025 Filed under: Inch and Mil-Spec Keensert, keensert, Keenserts Frequently Asked Questions | Tags: Expert Answers to Keenserts Frequently Asked Questions, Keensert FAQs Part 2, Keensert Guide, Keensert Inserts, Keensert Materials Available, Keensert Supplier, Key Locking Inserts, Self-Locking Keensert Leave a comment
In this second part of our three-part series, Top 17 Keensert® Frequently Asked Questions, we dive deeper into selecting the ideal key-locking inserts (a.k.a. Keenserts®) for your specific application. We’ll cover available insert materials—ranging from stainless steel and carbon steel to specialty alloys like 4140—and explain key sizing and thread-fit considerations. You’ll discover why key-locking inserts feature slightly oversized OD, and whether different lengths are available for various sizes. We will also share a simple visual trick that makes it easy to distinguish between self-locking and non-self-locking Keenserts®. Finally, we’ll offer practical advice for choosing the right key-locking insert material for your projects.
8. In what materials are key-locking inserts available off-the-shelf?
Key-locking inserts are commonly available off the shelf in carbon steel (black-phosphate steel) and 303 stainless steel. Additional materials include A4140, A286, and Nitronic 60, which may require a lead time and/or a minimum order.
Note: All sizes may not be available in all materials.
9. Do key-locking inserts come in different lengths?
Yes, key-locking inserts come in different lengths to accommodate various application requirements. The length of each key-locking insert is preset and is a function of the insert’s internal and external diameter. This ratio is usually determined by the manufacturer and can vary based on the thread size, material thickness, and the desired strength of the threaded connection.
Note: When selecting a key-locking insert, the length is usually chosen based on the thickness of the parent material and the load requirements. Thinwall key-locking inserts are often shorter, while heavy-duty or solid inserts may be longer to provide greater thread engagement and strength.
10. Why are the measurements of the outer diameters of Keensert® style key-locking inserts slightly larger than the standard UNC or UNF thread tolerances?
The outer diameter of key-locking inserts is slightly larger to ensure a tight fit and sufficient thread engagement in the parent material, compensating for tapped hole variations.
11. Why are self-locking Keenserts® a darker color than non-self-locking Keenserts®?
Self-locking Keenserts® are often treated with a dry-film lubricant that makes them easier to install and can result in a darker appearance compared to non-self-locking types.
12. How do I select the correct key-locking inserts material for my application?
The material choice for a key-locking insert depends on the application’s requirements, such as strength, corrosion resistance, temperature tolerance, parent material and environment. Generally speaking, 303 and Nitronic 60 stainless steel are more common for harsh environments, and carbon steel (i.e., black-phosphate steel) is used for general applications. We recommend reaching out to us or consulting a fastener engineer as a best practice.
Stay tuned for the next and final installment in this series, where we’ll cover advanced topics including how Keenserts® style key-locking inserts stack up against alternative threaded inserts, such as helical inserts (AKA HeliCoil®), and clarify common misconceptions.
Remember, expert advice is just a click away. If you have any questions, feel free to connect with our team or send us a request for quote and our team of sourcing experts will help you find what you need. “Finding the right screw for you” is our tag line after all!
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