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How many different threads are there?

The three standard thread series in the Unified screw thread system that are considered very important for fasteners are UNC (coarse), UNF (fine), and 8-UN (8 thread).

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The term fastener encompasses a relatively broad category of tools, such as screws, nuts, and bolts, that hold objects together. Typically, fasteners form a non-permanent joint. In other words, a fastener can be removed, and the separate pieces that were once joined should come apart without suffering any damage. As a counterexample, a welded joint isn’t a fastener. The exception to this rule is rivets, which fall under the category of fasteners but create permanent joints. Threaded fasteners are commonly used for a multitude of reasons. Aside from the obvious strength benefits (a fastener properly threaded or a bolted joint is much stronger than unthreaded alternatives), they are also reversible, meaning they can be taken apart after they are assembled. In addition, they are cost-efficient and available in a wide range of sizes. Because threaded fasteners like types of bolts, nuts, and washers can be used many times in a single application, they can add extra weight to a product. Additionally, they often need retightening when located in awkward places. They are susceptible to vibrations, and may need safety wire or other added features to further hold them in place and enable proper performance.

Nuts, bolts, and washers are all common types of threaded fasteners.

What is a thread fastener?

Fasteners can be threaded, fixed, and locking, while thread fasteners involve different screws. All threaded fasteners contain a spiraling ‘ramp’ on a cylindrical shaft. This ramp is a simple apparatus designed to change torque, or rotational force, into a linear force. It is called a thread. The thread of an external screw is described by: the pitch, which is defined by the length, parallel to the axis of the screw, between the crest of one thread to the adjacent crest; the major diameter, which is the outside diameter; the minor diameter, which is the lower diameter; the pitch diameter, the fictitious diameter for which the cuts and flanks of the threads are identical; and the lead, which is the axial distance the screw advances during a single rotation. A single start screw has the lead equal to the pitch. A screw with multiple threads has multiple edges next to each other and the double-start or double-threaded screw has the lead. A right-handed screw, when rotated clockwise, moves away from the user. With fasteners, the threads are generally right-handed and left-handed and must be identified.

Types of Threaded Fasteners

The three primary types of threaded fasteners are nuts, bolts, and screws.

Nuts

A common type of threaded fastener is a nut. It consists of a circular-shaped piece of metal with internal threads. Nuts are used together with bolts to join two or more components. The threaded interior of a nut joins to the threaded exterior of a bolt. When the nut is turned, it drives up or down the bolt, depending on the direction it’s turned. Most nuts have a hexagonal exterior. The inside is still cylindrical, though the exterior has a hexagonal shape to make installation easier. The six sides make hexagonal nuts easier to grip so that workers can install or remove them with minimal effort.

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Bolts

Bolts and screws are sometimes assumed to be the same thing, but this is a misconception. Bolts are used to connect two or more unthreaded objects, whereas screws are used to join two or more threaded objects. Another difference is that screws typically create their own threads during installation. Nonetheless, bolts are specifically designed to join unthreaded things by relying on a nut. As mentioned, nuts connect to bolts using their threaded surfaces. Thus, the threaded exterior of a bolt acts as a track for the threaded interior of a nut.

Screws

The most popular type of threaded fastener is a screw. Screws are made of cylindrical-shaped pieces of metal with a threaded surface wrapping around the sides. A head is on the top of a screw, which is used to drive the screw into an object or workpiece. For example, if a screw has a Phillips head, a Philips head screwdriver can be used to turn and install the screw. If a screw has a flat head, a flat head screwdriver or bit can be used. There are many different screw types, including machine screws, lag screws, hex screws, wood screws, drywall screws, self-tapping screws, and concrete screws.

There are many different types of screws.

Types of Screw Threads and Fastener Threads

Screw threads are the ridges of a uniform section in the form of a helix on a cylindrical fastener's external or internal surface. Internal threads denote those on nuts and tapped holes, while external threads are those on bolts, studs, or screws. The three standard thread series in the Unified screw thread system that are considered very important for fasteners are UNC (coarse), UNF (fine), and 8-UN (8 thread). Fine threads have larger stress areas which make the bolts stronger in tension. Their larger minor diameters create higher torsional and transverse shear strengths. They also can tap better in thin-walled members. With their smaller helix angle, they allow for closer adjustment accuracy. Coarse thread has stripping strengths that are greater for the same length of engagement. They have improved fatigue resistance and are less likely to cross thread. Coarse thread is also known for quicker assembly and disassembly, and to tap better in brittle materials. Their larger thread allowances permit thicker platings and coatings.

Unified National Coarse Threads

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Unified National Coarse threads, UNC threads, are the most common general fastener thread. Their fit is deeper and more generic than that of a fine thread, allowing for easy removal. Generally, they have a higher tolerance for manufacturing and plating, and do not need cross threading to assemble.

Unified National Fine Threads

Unified National Fine nuts and bolts have better torque-locking and load-carrying ability than UNC threads because of their larger minor diameter. Because of their more specific fit, they have tighter tolerances, finer tension adjustment, and can carry heavier loads. They are most commonly found in the aerospace industry.

United National Extra Fine Threads

A UNEF thread is finer than a UNF thread; they are used in applications with tapped holes in hard material, thin threaded walls, and tapped holes in thin material. As with UNF threads, UNEF threads are common in the aerospace industry.

UNJC and UNJF Threads

There are two types of “J” threads: external and internal. External UNJC and UNJF threads have a larger root radius than the corresponding part (either UNC, UNR, UNK, or UNF threads). The larger root radius results in a larger tensile area than the corresponding thread, and smaller stress concentration—bolts that carry heavy loads usually use “J” threads.

UNR and UNK Threads

A UNR external thread is the same as a UNC thread, only the root radius is rounded. There is no internal UNR thread. UNK threads resemble UNR threads, but the root radius and minor diameter require inspection.

Constant-Pitch Threads

These threads come in a variety of diameters to fit a given application—bolts with diameters of 1 in. and above commonly use pitches of 8, 12, or 16 threads per inch.

Conclusion

Above, we have looked at the different types of fastener threads, explained their applications, and their advantages and disadvantages. We hope this information has been helpful to you in your supplier search. To learn more about industry, or to make your own custom shortlist of suppliers, feel free to visit Thomasnet.com, which has information on other similar products.

How many different threads are there?

What are Cancers known for?

How do you know someone loves you?

Guides

Nuts, bolts, and washers are all common types of threaded fasteners.

What is a thread fastener?

Types of Threaded Fasteners

The three primary types of threaded fasteners are nuts, bolts, and screws.

Nuts

How can you tell if someone is spiritually awakened?

How does a man act when he's falling in love?

Bolts

Screws

There are many different types of screws.

Types of Screw Threads and Fastener Threads

Unified National Coarse Threads

What's the smallest age gap between siblings?

How do I get my 9 year old to sleep in his own bed?

Unified National Fine Threads

United National Extra Fine Threads

UNJC and UNJF Threads

UNR and UNK Threads

Constant-Pitch Threads

Conclusion

Other Fasteners Articles

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