A Free Running Coil Insert, also known as a wire thread insert or helical coil insert, is a precision-engineered internal thread insert designed to reinforce and protect internal threads in non-ferrous and low-strength materials. The free running coil insert provides a smooth, low-friction internal thread with no prevailing torque, allowing bolts or screws to be installed and removed freely.
Key Benefits of Free Running Coil Inserts
1.Improved Thread Strength
Free running coil inserts significantly increase load-carrying capacity in low-strength materials.
2.Extended Thread Life
The hardened stainless steel surface of the free running coil insert reduces wear during repeated assembly.
3.Even Load Distribution
The elastic design of free running coil inserts distributes stress uniformly along the thread length.
4.Smooth Assembly and Disassembly
Free running coil inserts allow bolts and screws to rotate freely with no prevailing torque.
5.High Resistance to Vibration and Impact
Free running coil inserts improve joint stability under dynamic loading conditions.
6.Efficient Thread Repair Solution
Free running coil inserts restore damaged threads quickly and economically.
Related Brand Product Display
Application for Heat Sinks Housing
Heat Sink Assembly
● Thread Reinforcement: Helicoils improve thread strength and wear resistance in aluminum 6061/6063, aluminum 1060, or copper C1100 heat sinks, preventing damage from frequent assembly and disassembly.
● Tolerance Compensation: Corrects machining deviations, ensuring stable assembly for M2/M2.5 precision screws and high-power IGBT modules.
● High Load Fixing: Provides sufficient strength for M5/M6 screws in soft aluminum heat sinks, securing heavy modules reliably.
● Anti-Loosening: Elastic structure increases friction, preventing thread loosening from temperature changes and vibration.
● Corrosion Resistance: Stainless steel Helicoils protect threads, extending heat sink service life.
Other Applications
● Aerospace: Enhances thread strength in lightweight structures, ensuring reliable assembly of satellites and precision instruments.
● Automotive Engines: Prevents thread loosening in engine blocks and cylinder heads, improving durability.
● Mold Manufacturing: Increases thread durability, reducing maintenance costs.
Technical Parameters of Unified Coarse Thread (UNC)
|
Nominal Diameter |
Pitch |
Nominal Length xD L |
Coil (W) |
Free-State OD(Dz) |
Drill Bit Diameter(do) |
Drilling Depth(L3) |
Actual Effective Length (L2) |
|
|
3/8''-16 |
1.588 |
1d |
9.50 |
4.4 |
11.8~12.2 |
10.0 |
15.9 |
8.7 |
|
1.5d |
14.3 |
7.2 |
20.7 |
13.5 |
||||
|
2d |
19.1 |
10.1 |
25.5 |
18.3 |
||||
|
2.5d |
23.8 |
12.9 |
30.2 |
23.0 |
||||
|
7/16''-14 |
1.814 |
1d |
11.1 |
4.5 |
13.4~14.0 |
11.6 |
18.4 |
10.2 |
|
1.5d |
16.7 |
7.4 |
24.0 |
15.8 |
||||
|
2d |
22.2 |
10.3 |
29.5 |
21.3 |
||||
|
2.5d |
27.8 |
13.1 |
35.1 |
26.9 |
||||
|
1/2''-13 |
1.954 |
1d |
12.7 |
4.8 |
15.2~15.8 |
13.2 |
20.5 |
11.7 |
|
1.5d |
19.1 |
7.9 |
26.9 |
18.1 |
||||
|
2d |
25.4 |
10.9 |
33.2 |
24.4 |
||||
|
2.5d |
31.8 |
13.9 |
39.6 |
30.8 |
||||
|
9/16''-12 |
2.117 |
1d |
14.3 |
5.1 |
17.0~17.6 |
14.9 |
22.8 |
13.2 |
|
1.5d |
21.5 |
8.3 |
30.0 |
20.4 |
||||
|
2d |
28.6 |
11.5 |
37.1 |
27.5 |
||||
|
2.5d |
35.7 |
14.7 |
44.2 |
34.6 |
||||
|
5/8''-11 |
2.309 |
1d |
15.9 |
5.3 |
18.9~19.5 |
16.6 |
25.1 |
14.7 |
|
1.5d |
23.8 |
8.3 |
33.0 |
22.6 |
||||
|
2d |
31.8 |
11.8 |
41.0 |
30.6 |
||||
|
2.5d |
39.7 |
15.0 |
48.8 |
38.5 |
||||
|
3/4''-10 |
2.540 |
1d |
19.1 |
5.9 |
22.4~23.0 |
19.7 |
29.3 |
17.8 |
|
1.5d |
28.6 |
9.4 |
38.8 |
27.3 |
||||
|
2d |
38.1 |
13.0 |
48.3 |
36.8 |
||||
|
2.5d |
47.6 |
16.6 |
57.8 |
46.3 |
||||
|
7/8''-9 |
2.822 |
1d |
22.2 |
6.3 |
26.0~26.7 |
23.0 |
33.5 |
20.8 |
|
1.5d |
33.3 |
10.0 |
44.6 |
31.9 |
||||
|
2d |
44.5 |
13.7 |
55.8 |
43.1 |
||||
|
2.5d |
55.6 |
17.4 |
66.9 |
54.2 |
||||
|
1''-8 |
3.175 |
1d |
25.4 |
6.4 |
29.6~30.4 |
26.2 |
38.1 |
23.8 |
|
1.5d |
38.1 |
10.2 |
50.8 |
36.5 |
||||
|
2d |
50.8 |
14.0 |
63.5 |
49.2 |
||||
|
2.5d |
63.5 |
17.8 |
76.2 |
61.9 |
||||
|
1 1/8''-7 |
3.629 |
1d |
28.6 |
6.3 |
33.4~34.4 |
29.5 |
43.1 |
26.8 |
|
1.5d |
42.9 |
10.0 |
57.4 |
41.1 |
||||
|
2d |
57.2 |
13.8 |
71.7 |
55.4 |
||||
|
1 1/4''-7 |
3.629 |
1d |
31.8 |
7.1 |
36.7~37.7 |
33.0 |
46.3 |
30.0 |
|
1.5d |
47.6 |
11.3 |
62.1 |
45.8 |
||||
|
2d |
63.5 |
15.4 |
78.0 |
61.7 |
||||
|
1 3/8''-6 |
4.234 |
1d |
34.9 |
6.6 |
40.6~41.7 |
36.0 |
51.8 |
32.8 |
|
1.5d |
52.4 |
10.6 |
69.3 |
50.3 |
||||
|
2d |
69.9 |
14.4 |
86.8 |
67.8 |
||||
Free Running Coil Insert Installation & Removal
Installation
Using the correct drill size for free running coil inserts ensures the STI thread minor diameter (Minor Ø) meets specification. Drill size selection depends on the STI thread size and parent material.
Detailed drill and tap dimensions, including Minor Ø limits and minimum drilling depth, are provided in the Locking Inserts Tech product data tables. Minimum depth varies with the STI tap type.
When multiple drill sizes are available, drilling near the upper Minor Ø limit is recommended, as it simplifies installation, extends tool life, and has minimal impact on joint strength.
Locking Inserts Tech recommends countersinking the hole where possible to aid helical wire insert installation. The countersink provides a lead-in for the first thread and improves installation smoothness.
The recommended countersink angle is 120° ±5°, with the diameter determined by the STI thread size. Refer to the Locking Inserts Tech product data tables for complete countersink dimensions.
Free-running coil inserts do not have a separate Class of Fit. The final thread fit is determined by the STI tap, such as 2B/3B (Unified) or 4H/5H (Metric).
Locking Inserts Tech recommends using STI cutting taps rather than thread-forming taps.
Minimum tapping depths for each size are listed in the Locking Inserts Tech product data tables and should be referenced during design and drawing review.
Verifying the dimensions of STI threads is a critical step before installing a coil insert. Locking Inserts Tech recommends using a graduated pin gage to check the Minor Ø, and a Go/No-Go STI gage to check the Pitch Ø and Major Ø.
After any surface treatment or plating is applied to the STI threads, gaging should be repeated, as coatings can significantly affect both insert installation and the final internal thread dimensions.
Note that locking inserts cannot be gaged once installed.
Follow the instructions provided with the installation tool to ensure proper insert installation. Additional copies of the instructions can be found on the Locking Inserts Tech installation tool product page.
The installation depth of the insert depends on the presence of a countersink: with a countersink, the insert should be 3/4 to 1-1/2 turns below the surface; without a countersink, 1/4 to 1/2 turn below the surface.
Locking Inserts Tech recommends always removing the tang when using locking inserts to ensure the bolt fully engages the entire length of the insert threads. For maximum assembly strength, the bolt must engage the full insert.
Use the Locking Inserts Tech Tang Break-off Tool to achieve a clean and precise tang removal. In blind holes, it may be necessary to remove the broken tang from the bottom of the hole (recommended).
Removal
Extraction Tool Method
Removing a helical coil insert can be challenging and usually requires a dedicated extraction tool. The tool's sharp edge is inserted into the top of the insert and lightly struck to engage it. Once seated, the insert is removed by turning it counterclockwise.
In some cases, a modified or custom tool is needed, such as a ground tap or drill, to reach inserts installed deep inside a hole.
Manual Removal Method
If an extraction tool cannot be used, pliers may be applied between the insert and the tapped hole. Once the insert is slightly lifted, it can be pulled out completely.
This method may damage the internal threads, so thread repair or re-tapping is often required. The removed insert is not reusable.
Workshop Display
SGS Report for Free Running Coil Insert
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