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Key-locking thread inserts

Materials:
Carbon Steel | Stainless Steel SUS303
Surface Treatment:
Carbon Steel: Phosphate Anti-Rust Treatment | Stainless Steel 303: Passivation Treatment
Size Classification:
Micro | Thin-Wall | Heavy-Duty | Reinforced
Internal Thread Size Range:
M2-M24

Custom solutions available upon customer request

Product Overview

Key-locking thread inserts are special fasteners with both internal and external threads, featuring two or four locking keys on the outer thread. After the insert is installed into the tapped hole, the keys are driven down to lock the insert in place, providing exceptional holding strength.
Today, they are widely used in aerospace, aviation, instrumentation, rail transit, hydraulic and electric equipment, chemical fiber machinery, textiles, and other applications requiring high thread strength.
The fundamental functions of key-locking inserts are thread repair and thread reinforcement. They offer a fast and effective method to restore damaged internal threads, and when used in low-strength materials, significantly enhance the strength of threaded holes.

Classification of Key-Locking Thread Inserts 

①By Material②Surface Treatment③By Type / Size Category 
Carbon steel |   Stainless steel SUS303Carbon steel — Phosphate anti-corrosion coating
Stainless steel 303 — Passivation
Miniature |  Thin-wall | Heavy-duty |  Extra-strength

 


Installation Process of Key-Locking Thread Inserts


  • image

  • 1.Drilling:

    The drilling depth should be greater than the length of the key-locking insert.

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  • 2.Tapping:

    The tapped thread specification must match the external thread size of the key-locking insert.

  • image

  • 3.Installation:

    Screw the key-locking insert into the corresponding threaded hole, ensuring it sits below the workpiece surface.

  • image

  • 4.Key Locking:

    Use the appropriate tool to drive the locking keys of the insert down into the bottom of the hole.

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  • 5.Completion:

    Illustration of the installation result.



Removal Method for Key-Locking Thread Inserts


  • 01

  • 01Drilling:

    Drill out a portion of the key-locking insert.

  • 02

  • 02 Breaking the Keys:

    Bend the locking keys inward and break them off.

  • 03

  • 03Removal:

    Use an “easy-out tool” or a similar tool to unscrew and remove the insert.

  • 04

  • 04Reinstallation:

    A new key-locking insert can then be installed.


Product Parameters

Specification Table for Key-locking Insert

Internal ThreadExternal ThreadLengthTap Drill SizeTapped Hole ThreadTap Depth
Miniature  
M2×0.4M4×0.733.4M4×0.74
M2.5×0.45M4.5×0.753.83.9M4.5×0.755
M3×0.5M5×0.84.24.4M5×0.85.5
M4×0.7M6×0.755.25.5M6×0.756.5
Thin-Wall
M5×0.8M8×1.2586.9M8×1.259.5
M6×1.0M10×1.25108.8M10×1.2511.5
M8×1.25M12×1.251210.8M12×1.2513.5
M8×1.0M12×1.251210.8M12×1.2513.5
M10×1.5M14×1.51412.8M14×1.515.5
M10×1.25M14×1.51412.8M14×1.515.5
M12×1.75M16×1.51614.75M16×1.517.5
M12×1.25M16×1.51614.75M16×1.517.5
 Heavy-Duty
M4×0.7M8×1.2586.9M8×1.259.5
M5×0.8M10×1.25108.8M10×1.2512.5
M6×1.0M12×1.251210.8M12×1.2514.5
M8×1.25M14×1.51412.8M14×1.516.5
M8×1.5M14×1.51412.8M14×1.516.5
M10×1.0M16×1.51614.75M16×1.518.5
M10×1.25M16×1.51614.75M16×1.518.5
M12×1.75M18×1.51816.75M18×1.520.5
M12×1.25M18×1.51816.75M18×1.520.5
M14×2.0M20×1.52018.75M20×1.522.5
M14×1.5M20×1.52018.75M20×1.522.5
M16×2.0M22×1.52220.5M22×1.524.5
M16×1.5M22×1.52220.5M22×1.524.5
M18×1.5M24×1.52422.5M24×1.526.5
M20×2.5M30×2.03028M30×2.034.5
M20×1.5M30×2.03028M30×2.034.5
M22×1.5M32×2.03230M32×2.036.5
M24×3.0M33×2.03331M33×2.037.5
M24×2.0M33×2.03331M33×2.037.5


ANSI Key-Locking Thread Insert Specifications

Internal ThreadExternal ThreadLengthTap Drill SizeTapped Hole ThreadTap Depth
Miniature  
2-568-320.120.1348-32-
4-4010-320.170.16110-32-
6-3212-280.170.18712-28-
8-321/4-280.220.2281/4-28-
Thin-Wall
10-245/16-187.96.45/16-189.4
10-325/16-187.96.45/16-189.4
1/4-203/8-169.48.53/8-1610.9
1/4-283/8-169.48.53/8-1610.9
5/16-187/16-1410.99.17/16-1412.4
5/16-247/16-1410.99.17/16-1412.4
3/8-161/2-1312.711.51/2-1314.2
3/8-241/2-1312.711.51/2-1314.2
7/16-149/16-1214.213.19/16-1215.7
7/16-209/16-1214.213.19/16-1215.7
1/2-135/8-1115.714.75/8-1117.2
1/2-205/8-1115.714.75/8-1117.2
Heavy-Duty
8-325/16-187.96.45/16-189.4
10-243/8-167.96.43/8-169.4
10-323/8-167.96.43/8-169.4
1/4-207/16-149.49.17/16-1410.9
1/4-287/16-149.49.17/16-1410.9
5/16-181/2-1310.911.51/2-1312.4
5/16-241/2-1310.911.51/2-1312.4
3/8-169/16-1212.713.19/16-1214.2
3/8-249/16-1212.713.19/16-1214.2
7/16-145/8-1115.714.75/8-1117.2
7/16-205/8-1115.714.75/8-1117.2
1/2-133/4-1615.717.83/4-1617.2
1/2-203/4-1615.717.83/4-1617.2
9/16-123/4-1620.617.83/4-1622.1
9/16-183/4-1620.617.83/4-1622.1
5/8-117/8-1422.021.07/8-1423.5
5/8-187/8-1422.021.07/8-1423.5


Thread Insert Production Process

Crafted with Skill·Made with Dedication — The Art of Precision Thread Insert Manufacturing

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Recommended Applications

Key-locking thread inserts Today,they are widely used in aerospace, aviation, instrumentation, rail transit, hydraulic and electric equipment, chemical fiber machinery, textiles, and other applications requiring high thread strength.

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Tangless wire thread insert

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Tang-Type Helical Inserts

Tang-Type Helical Inserts

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Key-locking thread inserts

Key-locking thread inserts

Key-locking thread inserts are special fasteners with both internal and external threads, featuring two or four locking keys on the outer thread. After the insert is installed into the tapped hole, the keys are driven down to lock the insert in place, providing exceptional holding strength.Today, they are widely used in aerospace, aviation, instrumentation, rail transit, hydraulic and electric equipment, chemical fiber machinery, textiles, and other applications requiring high thread strength.The fundamental functions of key-locking inserts are thread repair and thread reinforcement. They offer a fast and effective method to restore damaged internal threads, and when used in low-strength materials, significantly enhance the strength of threaded holes.Classification of Key-Locking Thread Inserts ①By Material②Surface Treatment③By Type / Size Category Carbon steel |   Stainless steel SUS303Carbon steel — Phosphate anti-corrosion coatingStainless steel 303 — PassivationMiniature |  Thin-wall | Heavy-duty |  Extra-strength Installation Process of Key-Locking Thread Inserts1.Drilling:The drilling depth should be greater than the length of the key-locking insert.2.Tapping:The tapped thread specification must match the external thread size of the key-locking insert.3.Installation:Screw the key-locking insert into the corresponding threaded hole, ensuring it sits below the workpiece surface.4.Key Locking:Use the appropriate tool to drive the locking keys of the insert down into the bottom of the hole.5.Completion:Illustration of the installation result.Removal Method for Key-Locking Thread Inserts01Drilling:Drill out a portion of the key-locking insert.02 Breaking the Keys: Bend the locking keys inward and break them off.03Removal:Use an “easy-out tool” or a similar tool to unscrew and remove the insert.04Reinstallation: A new key-locking insert can then be installed.

Self-Tapping Helical Inserts

Self-Tapping Helical Inserts

Self-tapping thread inserts (also known as self-tapping sleeves) are fasteners with internal and external threads, featuring cutting holes or cutting slots. They do not require pre-tapping; instead, they are driven directly into the base material to form their own internal threads. They can also restore damaged or stripped threads while maintaining the original thread size.Self-tapping inserts are suitable for light alloys (aluminum, magnesium, zinc, and their alloys), cast iron, brass/bronze, thermoset plastics, laminates, and wood. They are widely used in automotive engines, transmission components, and other parts such as mirrors, heat sinks, and shock absorbers; in factory equipment such as flange joints, construction machinery, and fuel systems; in household appliances and office equipment; as well as in capacitors, high-current devices, RF and telecommunication systems, and dental equipment. In the military field, they are mainly used in tanks, fighter jets, naval vessels, and other equipment.Advantages of Self-Tapping Inserts Self-tapping inserts can cut their own threads, eliminating the need to pre-tap the base material, thus reducing production costs. They have a large contact area with the assembled part, providing high tensile strength, allowing the use of lower-strength materials in design. They can restore worn or stripped threads in the base material, allowing the continued use of the same screws. They offer excellent vibration resistance, preventing loosening. They fit tightly with the base material, providing good airtightness even when the base contains air bubbles. Self-tapping inserts are easy and quick to install, requiring only one assembly tool, with low cost and virtually no defect rate.Types of Self-Tapping Inserts 302 / 302H Type The 302 series is the most widely used among all self-tapping inserts. Its two slots serve as cutting edges and provide a slight inward locking effect. The 302H version adds a flange to the 302 type, significantly increasing pull-out strength and torque resistance.307 / 308 TypeThe 307 and 308 series are designed for difficult-to-cut materials. They feature a thicker wall and a shallower yet sharper external thread, and use three holes as cutting edges. The 308 is a reinforced version of the 307, with the only difference being the insert length. The 307H / 308H versions include a flange.317 / 318 TypeThe 317/318 series is specially designed to provide increased torque capacity and vibration resistance, achieved by inserting a pin that conforms to DIN 1437 standards.Common Materials for Self-Tapping InsertsCarbon SteelSuitable for lower-strength base materials such as aluminum alloys, copper alloys, and plastics.Stainless Steel 303Suitable for higher-strength materials such as cast iron.Installation Method for Self-Tapping InsertsMethod 1:When the installation quantity is small, a simple installation method can be used. This method uses a bolt and nut of the corresponding size. As shown in the illustration, fix the self-tapping insert onto the corresponding bolt, then secure it with a nut of the same specification so that the three components form a single unit. Use a wrench to drive the insert into the pre-drilled hole, then remove the bolt after installation.Method 2:When the installation quantity is large, a dedicated insert installation tool can be used. The procedure is illustrated below. The rear end of the tool has a hex head, which can be connected to a manual tap wrench or to electric/pneumatic tools.Step 1Drill or form the hole according to the recommended and verified diameter. Screw the self-tapping insert onto the manual installation tool with the cutting slot or cutting hole facing downward. Ensure that the tool’s tip does not extend beyond the upper cutting point or the upper edge of the slot.。Step 2Drive the insert vertically into the hole. During the first 1–2 threads of engagement, check for misalignment. If any deviation occurs, remove and realign immediately. Do not reverse the installation tool during the tapping process.Step 3When the insert reaches the intended depth (the top of the insert should sit approximately 0.2 mm below the work surface), hold the lower hex nut with a hex wrench and rotate counterclockwise to remove the installation tool.Installation PrecautionsFor different base materials, refer to the recommended drill size to perform the pre-drilled hole. When the material has higher hardness, slightly enlarge the hole diameter within the recommended drilling range.Position the slotted end or the three-hole end downward, secure the self-tapping insert onto the installation tool, and align it vertically with the workpiece. During initial insertion (1P–2P), ensure precise alignment with the pre-drilled hole; the tool must never be tilted. If misalignment occurs, do not reverse the tool—remove and realign before proceeding. After the insert has entered 1/3–1/2 of its length, reinstallation is no longer possible. Also, do not reverse the tool during installation, as this may cause insert failure.Once the insert reaches the designated depth, hold the hex section of the tool with a locking plate and reverse the wrench to detach the tool from the workpiece.

Helical Insert Tools and Installation Methods

Helical Insert Tools and Installation Methods

Taps for Wire Thread InsertsTaps for wire thread inserts are used to machine special internal threads for wire thread insert installation holes. They are manufactured according to the national standard GB3464-83 (Straight-shank machine and hand taps) and are made of W6Mo5Cr4V2 high-speed steel. They can be used for both machine and manual tapping.Straight-Flute TapsStraight-flute taps have a wide range of applications and can be used for both through-holes and blind holes, as well as for ferrous and non-ferrous metals. Suitable for both hand and machine tapping and are relatively inexpensive. However, they are less specialized — short-lead taps are used for blind holes, and long-lead taps are used for through-holes.Spiral-Flute TapsSpiral-flute taps are more suitable for blind holes, especially when used with dedicated tapping machines or machining centers. Chips are expelled backward during tapping, resulting in high cutting efficiency and good surface quality of the internal threads.Forming (Roll) TapsForming taps are ideal for machining tough non-ferrous metals, especially copper, aluminum alloy castings, and stainless steel. They produce internal threads through cold-forming, which yields high tensile and shear strength and better surface roughness.
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