What Important Terminologies You Should Know Before Purchasing Fasteners?

Estimated Read Time:

As we know, fasteners are mechanical devices that are designed to hold two or more bodies or surfaces in a definite position(s) with respect to each other.

There is a wide array of fasteners available in the market to fulfill this objective. But, which one is right for your requirement?

To answer this question and act as a buying guide, here are some terminologies that you must know about before making a purchase.

Important Fastener Terminologies

1. Age Harden

- The use of heat treatment at varying temperatures at intervals to harden and strengthen a fastener.


2. Anneal

- This is a technique used to lower the hardness and increase the toughness of a metal by using heat. This heat treatment is applied to all 300 series and most 400 series of stainless steel prior to manufacturing fasteners.


3. Austenitic

- It is a type of steel that is created by exposing steel, chromium, and nickel at high temperatures. The stainless steel derives its name from Sir Robert Williams Austen, an English metallurgist. Austenitic steels are of two types- 300 series and 200 series. Austenitic steel is best known for being resistant to corrosion, the reason why it is often used for stainless steel applications.


4. Binder Head

- Also known as binding head screws, these heads are somewhat similar to the pan head but are thicker with a deeper slot. These types of screws also have a 10% larger bearing surface than pan head screws.


5. Broach

- It is a toothed tool, used to remove unnecessary metal to form a profile that duplicates the profile of the broaching tool. Broaching can be either linear or rotary.


6. Captive Screw

- These fasteners are created to remain attached to guards or equipment.


7. Chamfer

- A conical surface found at the starting end of a fastener thread.


8. Cheese head

- This screw is defined by its cylindrical head type. It has a flat bearing surface, with a flat disc top and cylindrical sides. The height of cheese head screws is roughly about half of its diameter and normally features a slot drive.


9. Cold Forming

- It is the process of using mechanical force to press steel rods and/or coils of steel wire into a required shape. Steel products are manufactured at room temperature using mechanical pressure known as cold heading and thread rolling.


10. Creep Strength

- refers to the resistance of fasteners to stress under high temperatures.


11. Cut Threading

- it is the process used to form threads on fasteners by removing and cutting away unnecessary metal.


12. Deburr

- A type of finishing while producing fasteners to remove irregular edges, burrs, and small imperfections.


13. Discontinuities

- These are small or large deformities found on fasteners like tool marks, slight depressions on the surface, small cracks, folds, and seams.


14. Fatigue

- This refers to the internal failure of a fastener caused by inadequate tension and clamping force after its installation. Fatigue strength is the measurement of a fastener’s endurance by exhibiting the load it can accept without breaking under repeated load cycles.


15. Galling

- Also known as “seizing”.  Galling is caused due to the two metals sticking together in such a way that they cannot be loosened easily. Heat contributes to galling caused by high-speed fastener installation. The most effective treatment for galling is thread lubrication.


16. Gimlet Point

- It is a threaded point on a fastener, at a point angle of 45° to 50°. Gimlet point is applied on Type AB self-tapping screws and woodscrews.


17. Jam Nut

- It is a low-profile nut, half the length of a standard nut that is mainly used as a locknut, jammed up against a standard nut to lock the two in place. Jam nuts are also used where a standard nut would not fit.


18. Knurl

- This refers to the decorative or rough surface on a fastener.


19. Left-hand thread

- It is not a commonly used fastener. In the case of a left-hand thread, a nut has to be turned counterclockwise to get tightened on a bolt.


20. Martensitic

- It is a type of stainless steel that can be strengthened and hardened via heat and aging treatments. Martensitic steel is a good alternative for fabricating mechanical valves, medical and mechanical instruments, turbine parts, and other applications.


21. Machineability

-  The term indicates the pliable characteristics of metal when cutting or forming on screw machines.


22. Minor Diameter

- This refers to the smallest diameter of screw threads.


23. Oven/ Stove Head

- This is an old term used for truss head screws. It derives the name from an extra-wide low profile head with a slightly rounded top surface.


24. Passivating

- With the process of passivating, you can create a protective film to protect the stainless steel from further oxidation. This is achieved by dipping the fasteners into a nitric acid solution, which coats it with a layer of chromium oxide on the surface.


25. Pitch Diameter

- It is the measurement of the distance between two adjacent threads outside the diameter of the threads.


26. Proof Load

- This is a test that fasteners must undergo without showing significant deformation.


27. Roll Threading

- It is the process of creating the threads that we see on a fastener. This is achieved by rolling or pushing against fasteners. The procedure eliminates the need to remove any metal. Roll threading hardens the fastener material to make the threads stronger.


28. Root Diameter

- The minor diameter on screws and major diameter on nuts.


29. Semi-finished hex caps

- Stainless hex head cap screws that have dimensions similar to a finished fastener, with greater tolerances.


30. Shear strength

-Shear strength is the maximum load, applied at a right angle to the fastener's axis.


31. Stamping

- It is the process of die-cutting parts usually in cases of flat washers.


32. Tap

- It is the process of putting internal threads in a hole or nut. A fully threaded bolt is known as a tap bolt.


33. Torque or Torsion Strength

- It is the force used for tightening fasteners. This is the amount of force required to twist a fastener apart.


34. Tumbling

- This is used to toss fasteners around to clean them and increase their shine. The action is alike washing clothes in a dryer.


35. UNJ

- This is a basic Unified National thread series with an external thread-controlled root radius.


36.Undersize body

- It refers to the measurement of the shoulder of a fastener which equals the pitch diameter or less. This means that the shoulder is smaller than the outside diameter of the threads.


37. Washer Face

- This is the circular rim on the underside of the head of a bolt or on one side of a nut. It provides a flat surface for either bolts or nuts to firmly sit on.


38. Yield

- The resistance to a load pulling on the middle of a fastener until the fastener shows permanent deformation.


39. Yield Strength

- The amount of pressure required to cause permanent deformity.

So, these were some important terminologies of fasteners that you should know about prior to making a purchase as it will help you in making the right choices for your use.

KG Lilly is a renowned manufacturer of fasteners in the United States with an overall experience of over 60 years. For expert advice and more details about the materials and functions of fasteners, you can always get in touch with KG Lilly and get the advice that fits your requirements.

Leave a comment

Leave a comment

Please note, comments need to be approved before they are published.