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  • All Metal Lock   
  • Cap (Acorn)   
  • Castle   
  • Coupling   
  • Flange   
  • Flexloc   
  • Heavy Hex   
  • Hex (most common)   
  • High   
  • Jam   
  • Keps (K-Lock)   
  • Left Hand   
  • Machine Screw   
  • Nylon Insert Lock   
  • Slotted   
  • Square   
  • Stover Lock   
  • Tee   
  • Thick   
  • Two Way Lock   
  • Wing   

  • Click on a NUT type above to continue shopping...


    Nuts are used with anchors, bolts, screws, studs, threaded rods—and on any other fastener that has machine threads—to fasten just about anything to anything. There are many different types of nuts that are used in a variety different applications but broadly fall into two categories: plain and locking. What we will call standard nuts are the ones frequently encountered; locking types, in contrast, have a feature that "locks" the nut thread to the mating threads to resist loosening. Common nuts are listed in Table 1, or click on a type above for detailed information.

    By definition, "A nut is [a] block or sleeve having an internal thread designed to assemble with the external thread on a bolt, screw, or other threaded part. It may serve as a fastening means, an adjusting means, a means for transmitting motion, or a means for transmitting power with a large mechanical advantage and non-reversible motion."

    Unified inch coarse series (UNC, Unified National Coarse) threads tend to be more popular but Unified inch fine (UNF, Unified National Fine) threads are available too. Coarse threaded fasteners have fewer threads per inch than fine threaded fasteners because coarse threads are farther apart. Consequently, the larger the number of threads per inch, the finer the thread. Also, smaller sizes have more threads per inch than larger sizes—see Table 2 for a comparison between UNC and UNF threads per inch by nut size. Unless noted otherwise, right-hand threads are standard, so turn the nut clockwise to install and tighten. Left-hand threads, also called reverse threads, are available and sometimes abbreviated LH for left hand. (Left-hand threads are often used to prevent a rotating part from unscrewing itself...a classic example is bicycle pedals. The left pedal has left-hand threads and the right pedal has right-hand threads. That way, the pedals effectively tighten themselves as you pedal. Turnbuckles also have left- and right-hand threads.)

    Size refers to nominal thread diameter of the nut and must match the size of the mating thread. Sizes range from about #0 to 3 1/2"—typically, the smallest nuts are machine screw and the largest are heavy nuts. The size of small inch series fasteners is specified as a number size (often #0, smallest, to #12, largest); larger sizes (usually beginning at 1/4") are specified in inches, usually fractional rather than decimal. Other nut dimensions of interest are width across flats, which is wrench size, and thickness. Occasionally, width across corners is important because that is the largest width dimension of hex and square nuts.

    Some nuts are chamfered (beveled) on one side only while others are symmetrical and chamfered on both sides (double chamfered).

    To ensure full thread engagement with the nut, bolts/screws should be long enough to allow at least two full threads to extend beyond the nut face after tightening. Conversely, there should be two full threads exposed on the head side of the nut to make sure the nut can be properly tightened.

    The two most common types of nuts are hex (short for hexagon, which has six sides) and square (four sided) nuts. Hex nuts are more popular but square nuts have their advantages.

    Unlike materials such as stainless steel and brass, some steel nuts are available in different strength "grades" as designated by the ASTM (American Society for Testing and Materials) and SAE (Society of Automotive Engineers).

    Common materials include steel (unplated and plated—see more about finishes below), stainless steel, brass, silicon bronze, aluminum and nylon. Steel remains the least costly material followed by stainless steel; copper alloys (such as brass and silicon bronze) are the most expensive.

    Common finishes for steel are zinc plating and hot dip galvanizing. Zinc, the most popular and least expensive commercial plating, offers moderate corrosion resistance. Hot dip galvanized is a thick coating of zinc that protects against corrosion in harsh environments. Stainless steel, though, is a better choice when corrosion is of concern except when submerged in salt water without free oxygen where it can suffer from severe pitting corrosion. Unplated and uncoated steel nuts—referred to as plain finish—may also be available and are susceptible to rust. Not all types are available in all materials and finishes.

    When selecting a nut for use with a strength graded bolt, it is very important that the nut be a compatible grade or strength; one grade higher is also acceptable as one source states.

    Always follow the manufacturer's recommendations regarding nut reuse, thread lubricants/locking compounds and torque values. Do not apply standard torque values to prevailing torque lock nuts because the joint may not be tightened to the correct clamping force due to the additional friction of the locking element.

    It is advisable to match materials and finishes of nuts, washers and bolts/screws. When using hot dipped galvanized bolts, always use hot dipped galvanized nuts, which are overtapped (threaded larger than normal) to accommodate the thick zinc coating on the bolts (using a galvanized nut on a non-galvanized bolt will result in an unacceptably loose fit).

    Stainless steel nuts and bolts/screws used together are susceptible to thread galling and seizing. While it may not be completely preventable, it can be substantially reduced. A thread lubricant is the most effective method. Alternatively, stainless steel alloys having different hardnesses—like a 316 nut and a 304 bolt—have less tendency to gall.

    For more information, visit our Tech Data section.


    All Metal Lock Nuts

    • Grade B, Zinc Plated
    • Grade C, Cadmium & Wax, USA
    • Grade C, Zinc Plated
    All Metal Lock Nut Grade B
    Grade B
    All Metal Lock Nut Grade C
    Grade C

    Cap Nuts (Acorn Nuts)

    • Brass
    • Brass, Nickel Plated
    • Milled, Zinc Plated
    • Stainless Steel 304 (18-8)
    • Two Piece Pressed, Nickel Plated
    Cap Nut

    Castle Nuts

    • Plain Finish
    • Zinc Plated
    Castle Nut

    Coupling Nuts

    • Stainless Steel 304 (18-8)
    • Zinc Plated
    Coupling Nut

    Flange Nuts

    Flange Lock Nuts
    • Grade G, Phosphate & Oil Finish, USA
    • Grade G, Yellow Dichromate
    Serrated Flange Nuts
    • Serrated, Zinc Plated
    • Serrated, Stainless Steel
    Flange Lock Nut
    Flange Lock
    Serrated Flange Nut
    Serrated Flange

    Flexloc Nuts

    • Full Height Heavy, Cadmium Plated
    • Full Height Heavy, Plain Finish
    • Full Height Heavy, Stainless Steel
    • Full Height Light, Cadmium Plated
    • Full Height Light, Plain Finish
    • Full Height Light, Stainless Steel
    • Thin Height Heavy, Cadmium Plated
    • Thin Height Heavy, Plain Finish
    • Thin Height Light, Cadmium Plated
    • Thin Height Light, Plain Finish
    • Thin Height Light, Stainless Steel
    Flexloc Nut Full Height
    Full Height
    Flexloc Nut Thin Height
    Thin Height

    Heavy Hex Nuts

    • ASTM A325, Plain Finish
    • ASTM A325, Zinc Plated
    • Brass
    • Grade 2, Hot Dip Galvanized
    • Grade 2, Plain Finish
    • Grade 2, Zinc Plated
    • Grade 2H, Hot Dip Galvanized
    • Grade 2H, Plain Finish
    • Grade 2H, Zinc Plated
    • Stainless Steel 304 (18-8)
    • Stainless Steel 316
    Heavy Hex Nut

    Hex Nuts

    • Aluminum
    • Brass
    • Grade 2, Plain Finish
    • Grade 2, Zinc Plated
    • Grade 5, Zinc Plated ($)
    • Grade 5, Zinc Plated, USA ($$)
    • Grade 8, Plain Finish
    • Grade 8, Yellow Zinc Plated ($)
    • Grade 8, Yellow Zinc Plated, USA ($$)
    • Hot Dip Galvanized
    • Nylon
    • Silicon Bronze
    • Stainless Steel 304 (18-8)
    • Stainless Steel 316
    Hex Nut

    High Nuts

    • Heat Treated (Grade 8), Plain Finish
    • Heat Treated (Grade 8), Zinc Plated
    • Grade 5, Plain Finish
    • Grade 5, Zinc Plated
    High Nut

    Jam Nuts

    • Brass
    • Grade 2, Plain Finish
    • Grade 2, Zinc Plated
    • Grade 2, Heavy, Plain Finish
    • Grade 8, Zinc or Yellow Zinc Plated & Plain Finish
    • Stainless Steel 304 (18-8)
    Jam Nut

    Keps Nuts (K-Lock Nuts)

    • Zinc Plated
    Keps Nuts

    Left Hand Nuts

    • Finished, Grade 2, Plain Finish
    • Finished Jam, Plain Finish
    • Heavy, Plain Finish
    Left Hand Hex Nut
    Left Hand Jam Nut
    Left Hand Heavy Hex Nut

    Machine Screw Nuts

    • Brass
    • Nylon
    • Silicon Bronze
    • Stainless Steel 304 (18-8)
    • Stainless Steel 316
    • Zinc Plated
    • Zinc Plated
    Hex Machine Screw Nut
    Square Machine Screw Nut

    Nylon Insert Lock Nuts (Nylock Nuts)

    • Thin, Grade 2, Zinc Plated
    • Thin, Stainless Steel
    • Grade 2, Zinc Plated
    • Grade 8, Yellow Zinc Plated
    • Stainless Steel
    • Heavy, Grade 2, Zinc Plated
    • Machine Screw, Stainless Steel
    • Machine Screw, Grade 2, Zinc Plated
    Nylon Insert Lock Nut Thin
    Nylon Insert Lock Nut
    Nylon Insert Lock Nut Heavy
    Nylon Insert Lock Nut Machine Screw
    Machine Screw

    Slotted Nuts

    • Finished, Plain Finish
    • Finished, Zinc Plated
    • Heavy, Plain Finish
    Slotted Nuts

    Square Nuts

    • Machine Screw, Zinc Plated
    • Regular, Zinc Plated
    Square Nut Machine Screw
    Machine Screw
    Square Nut Regular

    Stover Lock Nuts

    • Cadmium Dichromate Plated
    Stover Lock Nut

    Tee Nuts

    • Zinc Plated
    Tee Nut

    Thick Nuts

    • Grade 8, Yellow Zinc Plated, USA
    • Grade 9, Alloy, Cadmium Dichromate Plated
    Thick Nut

    Two Way Lock Nuts

    • Zinc Plated
    Two Way Lock Nut

    Wing Nuts

    • Forged, Brass
    • Forged, Stainless Steel 304 (18-8)
    • Forged, Zinc Plated
    Wing Nut

    Table 1. Nuts. A listing of common nut types and styles.

    Unified Inch Coarse and Fine Threads

    Nut Size Threads per Inch
    No./Frac. Decimal UNC UNF
    0 0.0600 - 80
    1 0.0730 64 72
    2 0.0860 56 64
    3 0.0990 48 56
    4 0.1120 40 48
    5 0.1250 40 44
    6 [1/8] 0.1380 32 40
    8 [5/32] 0.1640 32 36
    10 [3/16] 0.1900 24 32
    12 0.2160 24 28
    1/4 0.2500 20 28
    5/16 0.3125 18 24
    3/8 0.3750 16 24
    7/16 0.4375 14 20
    1/2 0.5000 13 20
    9/16 0.5625 12 18
    5/8 0.6250 11 18
    3/4 0.7500 10 16
    7/8 0.8750 9 14
    1 1.0000 8 12
    1 1/8 1.1250 7 12
    1 1/4 1.2500 7 12
    1 3/8 1.3750 6 12
    1 1/2 1.5000 6 12
    1 3/4 1.7500 5 -
    2 2.0000 4 1/2 -
    2 1/4 2.2500 4 1/2 -
    2 1/2 2.5000 4 -
    2 3/4 2.7500 4 -
    3 3.0000 4 -
    3 1/4 3.2500 4 -
    3 1/2 3.5000 4 -
    3 3/4 3.7500 4 -
    4 4.0000 4 -

    Table 2. Unified Inch Coarse and Fine Threads.
    Nut size as a number/fraction and in decimal inches,
    and threads per inch for Unified inch coarse (UNC)
    and Unified inch fine (UNF) thread types. 1/8", 5/32"
    and 3/16" are stove bolt sizes and are UNC only.

    CI:NTS v1.0

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