McMaster-Carr logo
    Enter e-mail addresses in the fields below
    Message
    Cancel
    Comments
    E-mail address (if you would like a response)
    82 Products

    Locknuts with External-Tooth Lock Washer
    3D CAD models available

    Image of Product. Front orientation. ZoomedIn view. Locknuts. Locknuts with External-Tooth Lock Washer.
    To save on assembly time, these locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand. Once the nut is against your material surface, tighten it down with a wrench or socket to get the teeth to bite. Although these nuts install more quickly than nylon-insert locknuts, they don't hold up as well against vibration and can mar your material. As long as the washer stays intact, you can reuse them. Also known as Keps and K-lock nuts.
    Medium-Strength Steel
    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.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.
    Thread Size
    Wd.,
    mm
    Ht.,
    mm
    Fastener Strength
    Grade/Class
    Washer
    OD, mm
    Pkg.
    Qty.
    Pkg.
    Zinc-Plated Steel
    M3 × 0.5 mm5.53.3ISO Class 8
    7.1100000000000000000
    M4 × 0.7 mm74.1ISO Class 8
    8.510000000000000000
    M5 × 0.8 mm85.2ISO Class 8
    9.510000000000000000
    M6 × 1 mm106.2ISO Class 8
    1210000000000000000
    M8 × 1.25 mm138.5ISO Class 8
    15.5250000000000000
    M10 × 1.5 mm179.7ISO Class 8
    20.11000000000000000
     
    Black-Zinc-Plated Steel
    M3 × 0.5 mm5.53ISO Class 8
    7.110000000000000000
    M4 × 0.7 mm74.1ISO Class 8
    8.510000000000000000
    M5 × 0.8 mm85.2ISO Class 8
    9.510000000000000000
    M6 × 1 mm106.2ISO Class 8
    125000000000000000
    M8 × 1.25 mm138.5ISO Class 8
    15.52500000000000000
    M10 × 1.5 mm179.7ISO Class 8
    20.11000000000000000
     
    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.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.
    Thread
    Size
    Wd.
    Ht.
    Washer
    OD
    Pkg.
    Qty.
    Pkg.
    Zinc-Plated Steel
    4-40
    1/4"7/64"0.281"10000000000000000
    5-40
    5/16"9/64"0.344"10000000000000000
    6-32
    5/16"9/64"0.344"1000000000000000
    8-32
    11/32"5/32"0.375"1000000000000000
    10-24
    3/8"5/32"0.406"1000000000000000
    10-32
    3/8"5/32"0.406"1000000000000000
    12-24
    7/16"3/16"0.5"5000000000000000
    1/4"-20
    7/16"15/64"0.5"1000000000000000
    1/4"-28
    7/16"15/64"0.5"1000000000000000
    5/16"-18
    1/2"21/64"0.578"10000000000000000
    5/16"-24
    1/2"5/16"0.592"5000000000000000
    3/8"-16
    9/16"25/64"0.656"10000000000000000
    3/8"-24
    9/16"25/64"0.656"10000000000000000
    1/2"-13
    3/4"31/64"0.891"1000000000000000
     
    Black-Zinc-Plated Steel
    4-40
    1/4"1/8"0.281"1000000000000000
    6-32
    5/16"9/64"0.344"1000000000000000
    8-32
    11/32"5/32"0.375"1000000000000000
    10-24
    3/8"5/32"0.406"10000000000000000
    10-32
    3/8"5/32"0.406"10000000000000000
    1/4"-20
    7/16"7/32"0.5"10000000000000000
     
    Corrosion-Resistant Stainless Steel
    18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.
    Black-Oxide 18-8 Stainless Steel—Typically chosen for their appearance, these nuts have a dark, matte coating to create a finished look. They resist rust in wet and outdoor environments, but won't hold up to the harsh chemicals that 316 stainless steel can.
    Thread Size
    Wd.
    Ht.
    Washer
    OD
    Pkg.
    Qty.
    Pkg.
    18-8 Stainless Steel
    4-40
    1/4"1/8"0.281"10000000000000000
    4-48
    1/4"1/8"0.281"10000000000000000
    6-32
    5/16"9/64"0.344"1000000000000000
    8-32
    11/32"11/64"0.375"10000000000000000
    10-24
    3/8"11/64"0.406"10000000000000000
    10-32
    3/8"11/64"0.406"10000000000000000
    12-24
    7/16"11/64"0.5"5000000000000000
    1/4"-20
    7/16"15/64"0.5"5000000000000000
    1/4"-28
    7/16"15/64"0.5"5000000000000000
    5/16"-18
    1/2"21/64"0.578"250000000000000
    5/16"-24
    1/2"21/64"0.578"2500000000000000
    3/8"-16
    9/16"25/64"0.656"2500000000000000
    3/8"-24
    9/16"25/64"0.656"100000000000000
    1/2"-13
    3/4"7/16"0.871"100000000000000
    M3 × 0.5 mm5.5 mm3.3 mm6.5 mm5000000000000000
    M4 × 0.7 mm7 mm4.1 mm8.2 mm5000000000000000
    M5 × 0.8 mm8 mm5.2 mm9.5 mm250000000000000
    M6 × 1 mm10 mm6.2 mm11.5 mm250000000000000
    M8 × 1.25 mm13 mm8.5 mm15.1 mm50000000000000
    M10 × 1.5 mm17 mm9.7 mm19.2 mm500000000000000
     
    Black-Oxide 18-8 Stainless Steel
    M3 × 0.5 mm5.5 mm3.3 mm6.5 mm250000000000000
    M4 × 0.7 mm7 mm4.1 mm8.2 mm2500000000000000
    M5 × 0.8 mm8 mm5.2 mm9.5 mm2500000000000000
    M6 × 1 mm10 mm6.2 mm11.5 mm2500000000000000
     

    Narrow-Profile Locknuts with External-Tooth Lock Washer
    3D CAD models available

    Image of Product. Front orientation. Locknuts. Narrow-Profile Locknuts with External-Tooth Lock Washer.
    Since they're about 20% narrower, these locknuts fit in tight spaces where standard-profile nuts won't fit. They combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. Once the nut is against your material surface, tighten it down with a wrench or socket to get the teeth to bite. Although these nuts install more quickly than nylon-insert locknuts, they don't hold up as well against vibration and can mar your material. As long as the washer stays intact, you can reuse them. Also known as Keps and K-lock nuts.
    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.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    Thread
    Size
    Wd.
    Ht.
    Washer
    OD
    Pkg.
    Qty.
    Pkg.
    Zinc-Plated Steel
    6-32
    1/4"1/8"0.281"100000000000000000
    8-32
    5/16"9/64"0.344"10000000000000000
     
    Corrosion-Resistant Stainless Steel
    18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.
    Thread
    Size
    Wd.
    Ht.
    Washer
    OD
    Pkg.
    Qty.
    Pkg.
    18-8 Stainless Steel
    6-32
    1/4"3/32"0.344"100000000000000000
     

    Locknuts with Spring-Lock Washer
    3D CAD models available

    Image of Product. Front orientation. Locknuts. Locknuts with Spring-Lock Washer.
    The curved, spring-like washer grips surfaces more tightly than tooth-lock washers for better vibration resistance. These locknuts also install just as quickly since you can twist them into place by hand. Once the nut is against your material, tighten it down with a wrench or socket. The washer's smooth edges won't mar the surface like teeth can. As long as the washer stays intact, you can reuse these locknuts.
    Medium-Strength Steel
    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.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    Black-Oxide Steel—Typically chosen for their appearance, these nuts have a dark, matte coating to create a finished look. They offer minimal corrosion resistance, so they're best for dry environments.
    Thread Size
    Wd.,
    mm
    Ht.,
    mm
    Fastener Strength
    Grade/Class
    Washer
    OD, mm
    Pkg.
    Qty.
    Pkg.
    Zinc-Plated Steel
    M3 × 0.5 mm5.53.8ISO Class 8
    850000000000000000
    M4 × 0.7 mm74.2ISO Class 8
    1010000000000000000
    M5 × 0.8 mm85.3ISO Class 8
    1210000000000000000
    M6 × 1 mm106.6ISO Class 8
    14500000000000000
    M8 × 1.25 mm138.8ISO Class 8
    185000000000000000
    M10 × 1.5 mm1710.7ISO Class 8
    221000000000000000
    M12 × 1.75 mm1913.8ISO Class 8
    25.52500000000000000
     
    Black-Oxide Steel
    M3 × 0.5 mm5.53.5ISO Class 8
    105000000000000000
    M4 × 0.7 mm74.2ISO Class 8
    105000000000000000
    M5 × 0.8 mm85.3ISO Class 8
    125000000000000000
    M6 × 1 mm106.6ISO Class 8
    14250000000000000
     
    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.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    Black-Oxide Steel—Typically chosen for their appearance, these nuts have a dark, matte coating to create a finished look. They offer minimal corrosion resistance, so they're best for dry environments.
    Thread
    Size
    Wd.
    Ht.
    Washer
    OD
    Pkg.
    Qty.
    Pkg.
    Zinc-Plated Steel
    4-40
    1/4"9/64"0.328"25000000000000000
    6-32
    5/16"9/64"0.328"2500000000000000
    8-32
    11/32"3/16"0.375"5000000000000000
    10-32
    3/8"3/16"0.406"2500000000000000
    1/4"-20
    7/16"3/16"0.5"1000000000000000
     
    Black-Oxide Steel
    4-40
    1/4"9/64"0.328"5000000000000000
    6-32
    5/16"9/64"0.328"2500000000000000
    8-32
    11/32"3/16"0.375"1000000000000000
    10-32
    3/8"3/16"0.406"100000000000000
    1/4"-20
    7/16"3/16"0.5"1000000000000000
     

    Assortments of Locknuts with External-Tooth Lock Washer

    Image of Product. Front orientation. Locknuts. Assortments of Locknuts with External-Tooth Lock Washer.
    Image of Product. Front orientation. ZoomedIn view. Locknuts. Assortments of Locknuts with External-Tooth Lock Washer.
    With a range of sizes on hand, you can use these assortments to fasten a variety of parts. These locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. Once the nut is against your material surface, tighten it down with a wrench or socket to get the teeth to bite. Although these nuts install more quickly than nylon-insert locknuts, they don't hold up as well against vibration and can mar your material. As long as the washer stays intact, you can reuse them. Also known as Keps and K-lock nuts.
    Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.
    18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.
    No. of
    Pieces
    Locknuts Included
    Container
    Type
    Each
    Zinc-Plated Steel
    6004-40 (100 Pieces)
    6-32 (100 Pieces)
    8-32 (100 Pieces)
    10-24 (100 Pieces)
    10-32 (100 Pieces)
    1/4"-20 (100 Pieces)
    Plastic Box000000000000000
     
    18-8 Stainless Steel
    6004-40 (100 Pieces)
    6-32 (100 Pieces)
    8-32 (100 Pieces)
    10-24 (100 Pieces)
    10-32 (100 Pieces)
    1/4"-20 (100 Pieces)
    Plastic Box00000000000000
     
    back to top