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Distorted Thread | Flex-Top |
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Cotter Pin | Steel Insert |
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Top Lock | Center Lock |
About Nuts, Materials, and Finishes
More
High-Strength Steel Nylon-Insert Locknuts—Grade 8



A nylon insert grips the bolt to resist loosening without damaging threads. These nuts are reusable, but their holding power lessens with each use. Made from Grade 8 steel, they're about 25% stronger than medium-strength steel locknuts.
Steel locknuts without a finish are ready to be painted or finished.
Black-oxide steel locknuts have a dark surface color and are mildly corrosion resistant in dry environments.
Zinc yellow-chromate plated steel locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Medium-Strength Steel Nylon-Insert Locknuts—Grade 5

A nylon insert grips the bolt to resist loosening without damaging threads. These locknuts are reusable, but their holding power lessens with each use. They are suitable for fastening most machinery and equipment. A zinc plating provides corrosion resistance in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel—Grade 5 | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 3/4" | 220° | 25 | 000000000 | 000000 |
Low-Strength Steel Nylon-Insert Locknuts

These locknuts have a nylon insert that grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use. About half the strength of medium-strength steel locknuts, they're for light duty fastening applications, such as securing access panels.
Zinc-plated steel locknuts are corrosion resistant in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 3/4" | 220° | 25 | 000000000 | 000000 |
Mil. Spec. Low-Strength Steel Nylon-Insert Locknuts

Choose these locknuts for their adherence to strict military standards for material and construction. The nylon insert grips the bolt to resist loosening without damaging threads. These locknuts are reusable, but their holding power lessens with each use. A cadmium yellow-chromate plating provides corrosion resistance in wet environments and adds lubricity so they thread on smoothly.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Specifications Met | Pkg. Qty. | Pkg. | |
Cadmium Yellow-Chromate Plated Steel | |||||||
---|---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 3/4" | 250° | MS21044-N10 | 1 | 000000000 | 00000 |
18-8 Stainless Steel Nylon-Insert Locknuts

These locknuts have good chemical resistance and may be mildly magnetic. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 3/4" | 220° | 5 | 000000000 | 00000 |
Super-Corrosion-Resistant 316 Stainless Steel Nylon-Insert Locknuts

These locknuts have excellent resistance to chemicals and salt water. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use. They may be mildy magnetic.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
316 Stainless Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 3/4" | 220° | 1 | 000000000 | 00000 |
Low-Strength Steel Thin Nylon-Insert Locknuts

These locknuts are about half the height of standard nylon-insert locknuts. Use them in light duty low-clearance applications or jam one against a hex nut to hold it in place. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use.
Zinc-plated steel locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 25/64" | 220° | 50 | 000000000 | 000000 |
High-Strength Steel Thin Nylon-Insert Locknuts

Half the height of standard nylon-insert locknuts, use these in low-clearance applications or jam one against a hex nut to hold it in place. They have a nylon insert that grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use. Made from Grade 8 steel, they're about 25% stronger than medium-strength steel thin locknuts. All have a finish that resists corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel—Grade 8 | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 25/64" | 220° | 5 | 000000000 | 000000 |
Medium-Strength Steel Thin Nylon-Insert Locknuts

Half the height of standard nylon-insert locknuts, use these locknuts in low-clearance applications or jam one against a hex nut to hold it in place. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use. These nuts are suitable for fastening most machinery and equipment when used in conjunction with a standard hex nut. All have a finish that resists corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel—Grade 5 | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 25/64" | 220° | 5 | 000000000 | 000000 |
18-8 Stainless Steel Thin Nylon-Insert Locknuts

These locknuts have good chemical resistance and may be mildly magnetic. They're about half the height of standard nylon-insert locknuts. Use them in low-clearance applications or jam one against a hex nut to hold it in place. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 25/64" | 220° | 1 | 000000000 | 00000 |
Mil. Spec. 18-8 Stainless Steel Thin Nylon-Insert Locknuts

Choose these locknuts for their adherence to strict military standards for material and construction. They have good chemical resistance and may be mildly magnetic. About half the height of standard nylon-insert locknuts, use them in low-clearance applications or jam one against a hex nut to hold it in place. The nylon insert grips the bolt to resist loosening without damaging threads. They're reusable, but their holding power lessens with each use.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Insert Max. Temp., °F | Specifications Met | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | |||||||
---|---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 13/32" | 250° | MS21083C10, NASM21083 | 1 | 000000000 | 000000 |
High-Strength Steel Top-Lock Distorted-Thread Locknuts

An irregularly shaped thread at the top of the nut grips the bolt for a stronger hold than nylon-insert locknuts. They thread on from the bottom of the nut, allowing more threads to engage the bolt before tightening for easier installation than center-lock distorted thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable. Comparable in strength to Grade 8 bolts, they're about 25% stronger than medium-strength steel locknuts.
Steel locknuts without a finish are ready to be painted or finished.
Black-oxide locknuts are mildly corrosion resistant in dry environments and blend in with dark surfaces.
Black-phosphate, zinc-plated, and zinc yellow-chromate-plated locknuts resist corrosion in wet environments.
Zinc-flake-coated locknuts are more corrosion resistant in wet environments than zinc-plated and zinc yellow-chromate plated locknuts.
Cadmium-plated locknuts resist corrosion in wet environments and have good lubricity, so they thread on smoothly.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
Steel—ASTM Grade C | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 25 | 000000000 | 000000 |
Black-Oxide Steel—ASTM Grade C | |||||
5/8"-18 | 15/16" | 35/64" | 5 | 000000000 | 00000 |
Zinc-Plated Steel—ASTM Grade C | |||||
5/8"-18 | 15/16" | 35/64" | 25 | 000000000 | 00000 |
Zinc Yellow-Chromate-Plated Steel—ASTM Grade C | |||||
5/8"-18 | 15/16" | 35/64" | 5 | 000000000 | 0000 |
Zinc Flake-Coated Steel—ASTM Grade C | |||||
5/8"-18 | 15/16" | 35/64" | 1 | 000000000 | 0000 |
Cadmium-Plated Steel—ASTM Grade C | |||||
5/8"-18 | 15/16" | 35/64" | 25 | 000000000 | 00000 |
Medium-Strength Steel Top-Lock Distorted-Thread Locknuts—Grade 5


These locknuts have an irregularly shaped thread at the top of the nut that grips the bolt for a stronger hold than nylon-insert locknuts. They thread on from the bottom of the nut, allowing more threads to engage the bolt before tightening for easier installation than center-lock distorted thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable. Made from Grade 5 steel, they're suitable for fastening most machinery and equipment.
Black-oxide locknuts are mildly corrosion resistant in dry environments and blend in with dark surfaces.
Zinc-plated locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
18-8 Stainless Steel Top-Lock Distorted-Thread Locknuts

These locknuts have good chemical resistance and may be mildly magnetic. They have an irregularly shaped thread at the top of the nut that grips the bolt for a stronger hold than nylon-insert locknuts. These locknuts thread on from the bottom of the nut, allowing more threads to engage the bolt before tightening for easier installation than center-lock distorted thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 1 | 000000000 | 00000 |
High-Strength Steel Center-Lock Distorted-Thread Locknuts—Grade 8

These locknuts have an irregularly shaped thread in the middle of the nut that grips the bolt for a stronger hold than nylon-insert locknuts. Also known as reversible locknuts, they can be threaded on from either end. They're about three times stronger than low-strength steel locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable.
Zinc yellow-chromate plated steel locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
Zinc Yellow-Chromate Plated Steel—Grade 8 | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 5 | 000000000 | 00000 |
Low-Strength Steel Center-Lock Distorted-Thread Locknuts

An irregularly shaped thread in the middle of the nut grips the bolt for a stronger hold than nylon-insert locknuts. Also known as reversible locknuts, they can be threaded on from either end. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable. Use them in light duty fastening applications, such as securing access panels. A zinc plating provides corrosion resistance in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel—Grade 2 | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 25 | 000000000 | 000000 |
18-8 Stainless Steel Center-Lock Distorted-Thread Locknuts

These locknuts have good chemical resistance and may be mildly magnetic. They have an irregularly shaped thread in the middle of the nut that grips the bolt for a stronger hold than nylon-insert locknuts. Also known as reversible locknuts, they can be threaded on from either end. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 5 | 000000000 | 000000 |
Steel Flex-Top Locknuts for Heavy Vibration


Threads at the top of these locknuts expand to grip the bolt on all sides for a stronger hold than distorted-thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging the threads. These locknuts have equivalent strength to Grade 8 steel locknuts.
Black-oxide steel locknuts are mildly corrosion resistant and have a dark surface color.
Cadmium-plated steel locknuts are corrosion resistant in wet environments. The plating adds lubricity, so they thread on smoothly.
For technical drawings and 3-D models, click on a part number.
Mil. Spec. Steel Flex-Top Locknuts for Heavy Vibration

Choose these locknuts for their adherence to strict military standards for material and construction. Threads at the top of the nut expand to grip the bolt on all sides for a stronger hold than distorted-thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. These locknuts have equivalent strength to Grade 8 steel locknuts. A cadmium yellow-chromate plating provides corrosion resistance in wet environments and adds lubricity so they thread on smoothly.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Specifications Met | Pkg. Qty. | Pkg. | |
Cadmium Yellow-Chromate Plated Steel | ||||||
---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 49/64" | MS21045-10 | 1 | 000000000 | 000000 |
Steel Thin Flex-Top Locknuts for Heavy Vibration


About two-thirds the height of standard flex-top locknuts, use these in low-clearance applications or jam one against a hex nut to hold it in place. Threads at the top of the nut expand to grip the bolt on all sides for a stronger hold than distorted-thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. These locknuts have equivalent strength to Grade 8 steel locknuts.
Plain steel locknuts are uncoated and ready for painting.
Cadmium-plated locknuts are corrosion resistant in wet environments. The plating adds lubricity so they thread on smoothly.
For technical drawings and 3-D models, click on a part number.
Stainless Steel Thin Flex-Top Locknuts for Heavy Vibration

These 18-8 stainless steel locknuts have good chemical resistance and may be mildly magnetic. They're about two-thirds the height of standard flex-top locknuts. Use them in low-clearance applications or jam one against a hex nut to hold it in place. Threads at the top of the nut expand to grip the bolt on all sides for a stronger hold than distorted-thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | |||||
---|---|---|---|---|---|
5/8"-18 | 15/16" | 13/32" | 1 | 000000000 | 000000 |
Medium-Strength Steel Locknuts for use with Cotter Pins—Grade 5

Secure these hex slotted nuts by inserting a cotter pin or safety wire through the slots and a drilled hole in your bolt for mild loosening resistance. They’re not recommended for use on parts exposed to high vibration because the pin is prone to shearing under prolonged stress. Height includes the slots. Cotter pins are not included. They're zinc plated to resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | For Cotter Pin Dia. | Min. Slot Wd. | Min. Slot Dp. | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel—Grade 5 | ||||||||
---|---|---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 5/32" | 0.18" | 0.195" | 10 | 000000000 | 000000 |
Low-Strength Steel Locknuts for use with Cotter Pins


Secure these hex slotted nuts by inserting a cotter pin or safety wire through the slots and a drilled hole in your bolt for mild loosening resistance. They’re not recommended for use on parts exposed to high vibration because the pin is prone to shearing under prolonged stress. Height includes the slots. Cotter pins are not included. A zinc plating provides corrosion resistance in wet environments.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | For Cotter Pin Dia. | Min. Slot Wd. | Min. Slot Dp. | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel | ||||||||
---|---|---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 35/64" | 5/32" | 0.18" | 0.195" | 10 | 000000000 | 00000 |
Stainless Steel Locknuts for use with Cotter Pins


These locknuts have good chemical resistance and may be mildly magnetic. Also known as castle nuts, secure them by inserting a cotter pin or safety wire through the slots in the nut and a drilled hole in your bolt for mild loosening resistance. They’re not recommended for use on parts exposed to high vibration because the pin is prone to shearing under prolonged stress. Height includes the slots. Cotter pins are not included.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | For Cotter Pin Dia. | Min. Slot Wd. | Min. Slot Dp. | Pkg. Qty. | Pkg. | |
18-8 Stainless Steel | ||||||||
---|---|---|---|---|---|---|---|---|
5/8"-18 | 15/16" | 23/32" | 5/32" | 0.18" | 0.21" | 1 | 000000000 | 00000 |
Steel-Insert Locknuts for Extreme Vibration—Grade 5

When installed, the steel insert grips the threads and lifts away from the nut body, isolating the insert from the nut’s load to resist spinoff caused by vibration. These locknuts are often used in shakers and vibrating equipment. The strength of the bolt should match the strength of the nut to prevent damaging threads. Made from Grade 5 steel, they're suitable for fastening most machinery and equipment.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Each | |
Steel—Grade 5 | ||||
---|---|---|---|---|
5/8"-18 | 15/16" | 5/8" | 000000000 | 00000 |
Thin Steel-Insert Locknuts for Extreme Vibration

About two-thirds the height of standard steel-insert locknuts, use these in low-clearance applications or jam one against a hex nut to hold it in place. When installed, the steel insert grips the threads and lifts away from the nut body, isolating the insert from the nut’s load to resist spinoff caused by vibration. They're often used in shakers and vibrating equipment. The strength of the bolt should match the strength of the nut to prevent damaging threads. Made from Grade 8 steel, these nuts are suitable for fastening most machinery and equipment.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Each | |
Steel—Grade 8 | ||||
---|---|---|---|---|
5/8"-18 | 15/16" | 15/32" | 000000000 | 00000 |
Two-Piece Thread-Clamping Locknuts for Extreme Vibration

Also known as drake style nuts, these include a two-piece clamp that expands to grip the bolt on all sides and a concave jam nut that clamps the threads onto the bolt for added vibration resistance. Use them with medium-strength steel bolts to prevent damaging threads. Height includes both nuts once assembled.
For technical drawings and 3-D models, click on a part number.
Thread Size | Wd. | Ht. | Each | |
Steel | ||||
---|---|---|---|---|
5/8"-18 | 15/16" | 55/64" | 000000000 | 000000 |
Low-Strength Steel Serrated Flange Locknuts

Serrations grip the material surface instead of the threads for easy installation and mild vibration resistance. The flange distributes pressure where the nut meets the material surface, eliminating the need for a separate washer. About half the strength of medium-strength steel flange locknuts, use them in light duty fastening applications, such as securing access panels. Height includes the flange.
Black-oxide steel flange locknuts are mildly corrosion resistant and have a dark surface color.
Zinc-plated steel flange locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.
High-Strength Steel Distorted-Thread Flange Locknuts

An irregularly-shaped thread grips the bolt for a stronger hold than nylon-insert flange locknuts. They have a flange that distributes pressure where the nut meets the material surface, eliminating the need for a separate washer. Grade G locknuts are comparable in strength to Grade 8 bolts. Height includes the flange.
Black-oxide steel locknuts are mildly corrosion resistant.
Zinc yellow-chromate plated steel locknuts resist corrosion in wet environments.
For technical drawings and 3-D models, click on a part number.