McMaster-Carr logo
    Filter by
    System of Measurement
    Color
    Fastener Strength Grade/Class
    Hex Nut Profile
    Industrial Info Compare
    Thread Type
    Industrial Info Compare
    Thread Spacing
    Industrial Info Compare
    Thread Direction
    Locking Type
    DFARS Specialty Metals
    Industrial Info Compare
    Fastener Strength Rating
    U.S.–Mexico–Canada Agreement (USMCA) Qualifying
    Export Control Classification Number (ECCN)
    Industrial Info Snippet
    Cap Nut Profile
    Forward
    Enter e-mail addresses in the fields below
    Message
    Cancel
    Print
    How can we improve?
    Comments
    E-mail address (if you would like a response)
    85 Products
    About Hex Nuts
    industrial info icon

    Choose a hex nut with the right profile, material, and strength for your application.

    Hex Nuts

    The most commonly used hex nuts, these are suitable for fastening most machinery and equipment.
    Medium-Strength Steel
    Image of Product. Front orientation. Hex Nuts. Hex Nuts.
    Image of Specification. Front orientation. Hex Nuts. Hex Nuts.
    These Grade 5 or Class 8 nuts are your go-to for fastening most machinery and equipment. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread Size
    Wd.
    Ht.
    Fastener Strength
    Grade/Class
    Specs. Met
    Pkg.
    Qty.
    Pkg.
    Black Corrosion-Resistant-Coated Steel
    1/4"-20
    		7/16"7/32"SAE Grade 5
    		ASME B18.2.21098797A02900000
    5/16"-18
    		1/2"17/64"SAE Grade 5
    		ASME B18.2.21098797A03000000
    3/8"-16
    		9/16"21/64"SAE Grade 5
    		ASME B18.2.2598797A0310000
    7/16"-14
    		11/16"3/8"SAE Grade 5
    		ASME B18.2.2598797A3300000
    1/2"-13
    		3/4"7/16"SAE Grade 5
    		ASME B18.2.2598797A5230000
    9/16"-12
    		7/8"31/64"SAE Grade 5
    		ASME B18.2.2598797A39500000
    5/8"-11
    		15/16"35/64"SAE Grade 5
    		ASME B18.2.2198797A5350000
    3/4"-10
    		1 1/8"41/64"SAE Grade 5
    		ASME B18.2.2198797A8550000
    M6 × 1 mm10 mm5 mmClass 8DIN 9341098797A3210000
    M8 × 1.25 mm13 mm6.5 mmClass 8DIN 9341098797A32200000
    M10 × 1.5 mm17 mm8 mmClass 8DIN 9341098797A32300000
    M12 × 1.75 mm19 mm10 mmClass 8DIN 934598797A3240000
     
    High-Strength Steel
    Image of Product. Front orientation. Hex Nuts. Hex Nuts.
    Image of Specification. Front orientation. Hex Nuts. Hex Nuts.
    Rated Grade 8, Grade C, or Class 10, these nuts are about 25% stronger than medium-strength steel nuts. They are commonly used to fasten components in valves, pumps, motors, and other high-stress applications. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread Size
    Wd.
    Ht.
    Fastener Strength
    Grade/Class
    Specs. Met
    Pkg.
    Qty.
    Pkg.
    Black Corrosion-Resistant-Coated Steel
    1/4"-20
    		7/16"7/32"SAE Grade 8
    		ASME B18.2.21098797A121000000
    5/16"-18
    		1/2"17/64"SAE Grade 8
    		ASME B18.2.21098797A12200000
    3/8"-16
    		9/16"21/64"SAE Grade 8
    		ASME B18.2.2598797A1230000
    1/2"-13
    		3/4"7/16"SAE Grade 8
    		ASME B18.2.2598797A12400000
    M6 × 1 mm10 mm5 mmClass 10DIN 9341098797A22100000
    M8 × 1.25 mm13 mm6.5 mmClass 10DIN 9341098797A22200000
    M10 × 1.5 mm17 mm8 mmClass 10DIN 9341098797A22300000
    M12 × 1.75 mm19 mm10 mmClass 10DIN 934598797A2240000
     
    Lightweight Aluminum
    Image of Product. Front orientation. Hex Nuts. Hex Nuts.
    Image of Specification. Front orientation. Hex Nuts. Hex Nuts.
    Black Corrosion-Resistant-Coated 6061 Aluminum—Offers better rust resistance than plain aluminum. Also known as black luster, the coating creates a finished appearance and has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. One-third the weight of steel, these nuts are suitable for robotics, automation, and other applications that have weight limitations.
    Thread
    Size
    Wd.
    Ht.
    Specs. Met
    Pkg.
    Qty.
    Pkg.
    Black Corrosion-Resistant-Coated 6061 Aluminum
    8-32
    		11/32"1/8"ASME B18.2.2599149A11200000
    10-24
    		3/8"1/8"ASME B18.2.2599149A1150000
    10-32
    		3/8"1/8"ASME B18.2.2599149A1180000
    1/4"-20
    		7/16"7/32"ASME B18.2.2599149A1210000
    5/16"-18
    		1/2"17/64"ASME B18.2.2599149A1240000
    3/8"-16
    		9/16"21/64"ASME B18.2.2599149A12700000
    1/2"-13
    		3/4"7/16"ASME B18.2.2199149A1300000
     

    Nylon-Insert Locknuts

    Versatile yet economical, these are the most commonly used locknuts. The nylon insert grips the screw to prevent loosening from moderate vibration without damaging threads. However, the insert may become brittle if exposed to high temperatures. These locknuts are reusable a handful of times, but the holding power decreases with each use.
    High-Strength Steel
    Image of Product. Front orientation. Locknuts. Nylon-Insert Locknuts.
    Rated Grade 8, Grade C, or Class 10, these locknuts are about 25% stronger than medium-strength steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black-Corrosion-Resistant-Coated Steel—These nuts combine a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread Size
    Wd.,
    mm
    Ht.,
    mm
    Fastener Strength
    Grade/Class
    Insert Max.
    Temp., ° F
    Specs.
    Met
    Pkg.
    Qty.
    Pkg.
    Black-Corrosion-Resistant-Coated Steel
    M4 × 0.7 mm75Class 10220DIN 985590237A110000000
    M5 × 0.8 mm85Class 10220DIN 985590237A12000000
    M6 × 1 mm106Class 10220DIN 985590237A13000000
    M8 × 1.25 mm138Class 10220DIN 985590237A14000000
    M10 × 1.5 mm1710Class 10220DIN 985590237A15000000
    M12 × 1.75 mm1912Class 10220DIN 985190237A1600000
    M14 × 2 mm2214Class 10220DIN 985190237A1700000
     
    Medium-Strength Steel
    Image of Product. Front orientation. Locknuts. Nylon-Insert Locknuts.
    These Grade 5 or Class 8 nuts are your go-to for fastening most machinery and equipment. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black-Corrosion-Resistant-Coated Steel—These nuts combine a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread Size
    Wd.,
    mm
    Ht.,
    mm
    Fastener Strength
    Grade/Class
    Insert Max.
    Temp., ° F
    Specs. Met
    Pkg.
    Qty.
    Pkg.
    Black-Corrosion-Resistant-Coated Steel
    M4 × 0.7 mm75Class 8220DIN 985, ISO 10511590819A111000000
    M5 × 0.8 mm85Class 8220DIN 985, ISO 10511590819A11200000
    M6 × 1 mm106Class 8220DIN 985, ISO 10511590819A11300000
    M8 × 1.25 mm138Class 8220DIN 985, ISO 10511590819A11400000
    M10 × 1.5 mm1710Class 8220DIN 985, ISO 10511590819A11500000
    M12 × 1.75 mm1912Class 8220DIN 985, ISO 10511190819A1160000
    M14 × 2 mm2214Class 8220DIN 985, ISO 10511190819A1170000
     
    Low-Strength Steel
    Image of Product. Front orientation. Locknuts. Nylon-Insert Locknuts.
    Rated Grade 2, Class 6, or lower, these locknuts are about half as strong as medium-strength steel nuts. Use them with screws that have a similar strength rating to avoid stripping threads during installation.
    Black-Corrosion-Resistant-Coated Steel—These nuts combine a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread
    Size
    Wd.
    Ht.
    Insert Max.
    Temp., ° F
    Pkg.
    Qty.
    Pkg.
    Black-Corrosion-Resistant-Coated Steel
    6-32
    		5/16"11/64"220591333A11000000
    8-32
    		11/32"15/64"220591333A1200000
    10-24
    		3/8"15/64"220591333A1300000
    10-32
    		3/8"15/64"220591333A1400000
    1/4"-20
    		7/16"5/16"220591333A1500000
    5/16"-18
    		1/2"11/32"220591333A1600000
    3/8"-16
    		9/16"29/64"220591333A1700000
    1/2"-13
    		3/4"19/32"220591333A18000000
     

    Nylon-Insert Flange Nuts

    A nylon insert grips the screw for a stronger hold than a serrated flange, without damaging threads or marring the surface of your material. However, the insert may become brittle if exposed to high temperatures. These nuts have a flange that distributes pressure evenly across the mounting surface, so you don't need a separate washer. They are ideal for securing screws in oversized or irregularly shaped holes since the flange covers a larger area than standard nuts. You can reuse them a handful of times, but their holding power will decrease with each use. Also known as collar nuts.
    Medium-Strength Steel
    Image of Product. Front orientation. Flange Nuts. Nylon-Insert Flange Nuts.
    Rated Grade 5, Grade F, or Class 8, these nuts are your go-to for fastening most machinery and equipment. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Flange,
    mm
    Thread Size
    Wd.,
    mm
    Ht.,
    mm
    Dia.
    Thk.
    Fastener Strength
    Grade/Class
    Specs.
    Met
    Insert Max.
    Temp., ° F
    Pkg.
    Qty.
    Pkg.
    Black Corrosion-Resistant-Coated Steel
    M5 × 0.8 mm87.111.81Class 8DIN 6926250597071A10100000
    M6 × 1 mm109.114.21.1Class 8DIN 6926250597071A1020000
    M8 × 1.25 mm1311.117.91.2Class 8DIN 6926250597071A1030000
    M12 × 1.75 mm1816.1261.8Class 8DIN 6926250597071A10400000
     

    Cap Nuts

    Conceal and protect protruding screw threads while fastening parts together. These nuts help prevent damage to surrounding materials and reduce injuries. Also known as acorn nuts, they have a smooth, rounded head that creates a finished look.
    Low-Strength Steel
    Image of Product. Front orientation. Cap Nuts. Cap Nuts.
    Rated Grade 2, Class 6, or lower, these nuts are about half as strong as medium-strength steel nuts. They are suitable for light duty fastening applications, such as securing access panels. Use them with screws that have a similar strength rating to avoid stripping threads during installation.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Pkg.
    Thread
    Size
    Thread
    Dp.
    Wd.
    Ht.
    Pkg.
    Qty.
    1-9
    10-49
    50-Up
    Black Corrosion-Resistant-Coated Steel
    4-40
    		5/32"1/4"1/4"1098667A101000000000000000000
    6-32
    		5/32"5/16"11/32"1098667A110000000000000000
    8-32
    		5/32"5/16"11/32"1098667A130000000000000000
    10-24
    		3/16"3/8"13/32"598667A150000000000000
    10-32
    		3/16"3/8"13/32"598667A190000000000000
    1/4"-20
    		1/4"7/16"15/32"598667A210000000000000
    5/16"-18
    		5/16"1/2"17/32"598667A2300000000000000
    3/8"-16
    		3/8"9/16"5/8"198667A250000000000000
    7/16"-14
    		7/16"5/8"11/16"198667A601000000000000
    1/2"-13
    		1/2"3/4"13/16"198667A102000000000000
    9/16"-12
    		9/16"7/8"15/16"198667A695000000000000
    5/8"-11
    		5/8"15/16"1"198667A706000000000000
     
    Medium-Strength Steel
    Image of Product. Front orientation. Cap Nuts. Cap Nuts.
    About twice as strong as low-strength steel, these Grade 5 nuts fasten most machinery and equipment. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Pkg.
    Thread
    Size
    Thread
    Dp.
    Wd.
    Ht.
    Fastener Strength
    Grade/Class
    Pkg.
    Qty.
    1-9
    10-49
    50-Up
    Black Corrosion-Resistant-Coated Steel
    1/4"-20
    		1/4"7/16"15/32"SAE Grade 5
    		198858A558000000000000000
    5/16"-18
    		5/16"1/2"17/32"SAE Grade 5
    		198858A570000000000000
    3/8"-16
    		3/8"9/16"5/8"SAE Grade 5
    		198858A640000000000000
    1/2"-13
    		1/2"3/4"13/16"SAE Grade 5
    		198858A849000000000000000
     
    High-Strength Steel
    Image of Product. Front orientation. Cap Nuts. Cap Nuts.
    Rated Grade 8 or Class 10, these nuts are about 25% stronger than medium-strength steel nuts. They are commonly used to fasten components in valves, pumps, motors, and other high-stress applications. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.
    Black Corrosion-Resistant-Coated Steel—Combines a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Pkg.
    Thread
    Size
    Thread
    Dp.
    Wd.
    Ht.
    Fastener Strength
    Grade/Class
    Pkg.
    Qty.
    1-9
    10-49
    50-Up
    Black Corrosion-Resistant-Coated Steel
    1/4"-20
    		1/4"7/16"15/32"SAE Grade 8
    		190767A111000000000000000
    5/16"-18
    		5/16"1/2"17/32"SAE Grade 8
    		190767A112000000000000
    3/8"-16
    		3/8"9/16"5/8"SAE Grade 8
    		190767A113000000000000
    1/2"-13
    		1/2"3/4"13/16"SAE Grade 8
    		190767A114000000000000000
     

    Thin-Profile Nylon-Insert Locknuts

    Image of Product. Front orientation. Locknuts. Thin-Profile Nylon-Insert Locknuts.
    About half the height of standard-profile locknuts, these fit in spaces with low clearance. You can also use them as jam nuts by threading them against a hex nut to hold it in place. The nylon insert grips the screw to prevent loosening from moderate vibration without damaging threads. However, the insert may become brittle if exposed to high temperatures. These locknuts are reusable a handful of times, but the holding power decreases with each use.
    Low-Strength Steel
    Rated Grade 2, Class 6, or lower, these locknuts are about half as strong as medium-strength steel nuts. Use them with screws that have a similar strength rating to avoid stripping threads during installation.
    Black-Corrosion-Resistant-Coated Steel—These nuts combine a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread
    Size
    Wd.
    Ht.
    Insert Max.
    Temp., ° F
    Pkg.
    Qty.
    Pkg.
    Black-Corrosion-Resistant-Coated Steel
    6-32
    		5/16"1/8"220591581A31500000
    8-32
    		11/32"11/64"220591581A3250000
    10-24
    		3/8"11/64"220591581A3350000
    10-32
    		3/8"11/64"220591581A3450000
    1/4"-20
    		7/16"13/64"220591581A3550000
    5/16"-18
    		1/2"1/4"220591581A3650000
    3/8"-16
    		9/16"17/64"220591581A3750000
    1/2"-13
    		3/4"5/16"220591581A3850000
     

    Thin-Heavy-Profile Nylon-Insert Locknuts

    Image of Product. Front orientation. Locknuts. Thin-Heavy-Profile Nylon-Insert Locknuts.
    About half the height of standard-profile locknuts and 10% wider, these fit in spaces with low clearance and handle heavier loads by distributing them over a larger area. You can also use them as jam nuts by threading them against a hex nut to hold it in place. The nylon insert grips the screw to prevent loosening from moderate vibration without damaging threads. However, the insert may become brittle if exposed to high temperatures. These locknuts are reusable a handful of times, but the holding power decreases with each use.
    Low-Strength Steel
    Rated Grade 2, Class 6, or lower, these locknuts are about half as strong as medium-strength steel nuts. Use them with screws that have a similar strength rating to avoid stripping threads during installation.
    Black-Corrosion-Resistant-Coated Steel—These nuts combine a finished appearance with the rust resistance of stainless steel. The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.
    Thread
    Size
    Wd.
    Ht.
    Insert Max.
    Temp., ° F
    Pkg.
    Qty.
    Pkg.
    Black-Corrosion-Resistant-Coated Steel
    1/4"-20
    		1/2"9/32"250590652A81000000
    5/16"-18
    		9/16"5/16"250590652A8200000
    3/8"-16
    		11/16"13/32"250190652A8300000
    1/2"-13
    		7/8"17/32"250190652A8400000
     
    back to top