Best Helical Threaded Inserts for 2026 That Hold Tight

Should you need a threaded repair that stays put, you will want the right insert for the material, load, and hole size.

In 2026, the best helical threaded inserts for metal and plastic are not one size fits all, and choosing poorly can leave you with another stripped thread.

From E-Z LOK repair kits to brass heat set options, the details matter more than you may expect, and a few of them can change everything.

More Details on Our Top Picks

1. E-Z LOK EZ-329-6 Thread Repair Kit for Metal

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   Best Metal Repair

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   If you are fixing stripped metal threads, this kit provides a reliable repair solution. You get the E-Z LOK EZ-329-6 kit with 13 pieces, including carbon steel inserts, a drill, a tap, and an installation drive tool. It is designed for 3/8-16 threads in aluminum, cast iron, and magnesium, so you can restore damaged holes and help prevent future stripping. The black oxide steel inserts use pre-applied adhesive that activates during installation for a secure hold. With a self-locking design and strong user ratings, this kit is a dependable choice for threaded repairs.

   • Thread Type:3/8-16
   • Material:Carbon steel
   • Kit Contents:Drill, tap, insert tool
   • Application:Metal repair
   • Pack Size:13 pieces
   • Corrosion Resistance:Black oxide finish
   • Additional Feature:Self-locking inserts
   • Additional Feature:Pre-applied adhesive
   • Additional Feature:Black oxide finish

2. E-Z Lok Helical Threaded Insert Kit 1/4″-28 (10-Pack)

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   Best Fine Threads

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   The E-Z Lok 1/4″-28 kit is ideal for fine-thread repair in soft metals. It quickly restores damaged holes in aluminum, cast iron, or magnesium, then reinforces them for lasting strength. Each 18-8 stainless steel coil resists corrosion and handles heat up to 800°F, so it performs well in demanding service conditions. The kit includes 10 inserts, an STI tap, and an installation tool, giving you everything needed for a clean install. With a 0.500″ installed length, this EK30820 kit provides compact, reliable thread support.

   • Thread Type:1/4-28
   • Material:18-8 stainless steel
   • Kit Contents:Inserts, STI tap, install tool
   • Application:Soft metals
   • Pack Size:10-pack
   • Corrosion Resistance:Corrosion resistant
   • Additional Feature:800°F temperature rating
   • Additional Feature:0.500-inch installed length
   • Additional Feature:STI tap included

3. E-Z Lok Helical Threaded Insert Kit (Pack of 10)

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   Best Small Threads

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   Need to repair small threads in soft metal? Use the E-Z Lok Helical Threaded Insert Kit (Pack of 10) to restore damaged threads and reinforce tapped holes quickly. It is made from 18-8 stainless steel wire for corrosion resistance and heat tolerance up to 800°F. The kit works well in aluminum, cast iron, and magnesium. Inside, you will find coil threaded inserts, an STI tap, and an installation tool. With the #12-24 size, 0.432-inch installed length, and EK20720 spec, you can fix threads with confidence.

   • Thread Type:#12-24
   • Material:18-8 stainless steel
   • Kit Contents:Inserts, STI tap, install tool
   • Application:Soft metals
   • Pack Size:10-pack
   • Corrosion Resistance:Corrosion resistant
   • Additional Feature:#12-24 thread size
   • Additional Feature:0.432-inch installed length
   • Additional Feature:STI tap included

4. E-Z Lok Helical Threaded Insert Kit (5-Pack)

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   Best Heavy Duty

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   Built for tough aluminum and cast iron repairs, the E-Z LOK EK21415 delivers heavy-duty thread restoration. It includes five 5/8-11 inserts, an STI tap, an installation tool, and a combo tang-break tool, so you can fix damaged threads quickly. Its 304 stainless steel construction resists corrosion and handles heat up to 800°F while providing 8,000 psi shear strength. Use it to reinforce tapped holes in aluminum, cast iron, magnesium, and other soft metals. The 0.938 inch installed length gives you solid grip in demanding metal repairs.

   • Thread Type:5/8-11
   • Material:304 stainless steel
   • Kit Contents:Inserts, STI tap, install tool, tang break tool
   • Application:Soft metals
   • Pack Size:5-pack
   • Corrosion Resistance:Corrosion resistant
   • Additional Feature:Combo tang-break tool
   • Additional Feature:55 MPa shear strength
   • Additional Feature:0.938-inch installed length

5. Kadrick Threaded Inserts Assortment Kit for 3D Printing

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   Best For 3D Printing

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   When you print functional parts, Kadrick’s threaded inserts make it easy to add strong threads. You can heat-set these brass inserts into plastic with a soldering iron, or use ultrasound for a clean fit. The kit includes M2, M3, M4, and M5 sizes, with heights from 3 mm to 12 mm, so you have options for common 3D printing jobs. Each insert is made from precision-processed brass, which resists corrosion, conducts heat well, and grips tightly thanks to the knurled design. You also get 520 pieces in labeled compartments, plus Kadrick’s 24-month support.

   • Thread Type:M2/M3/M4/M5
   • Material:Brass
   • Kit Contents:Inserts assortment kit
   • Application:3D printing/plastic
   • Pack Size:520 pcs
   • Corrosion Resistance:Brass corrosion resistance
   • Additional Feature:520-piece assortment
   • Additional Feature:Independent compartments
   • Additional Feature:Soldering iron installation

6. Premium Brass Threaded Inserts Assortment Kit with Tool

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   Best Assortment Kit

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   For 3D printing and plastic repairs, this premium brass kit provides a versatile assortment. It includes 607 pieces covering M2, M2.5, M3, M4, M5, and M6 sizes, plus a tool for easy heat setting. The brass construction resists oxidation, corrosion, breakage, and deformation, while its high thermal conductivity helps inserts bond cleanly in PLA, PETG, ABS, PPS, and PP. Spiral 45 degree knurling creates a strong grip in plastic, and the built in guides mean you do not need countersinking. Clear labels and sealed compartments keep every size organized.

   • Thread Type:M2/M2.5/M3/M4/M5/M6
   • Material:Brass
   • Kit Contents:Inserts assortment kit with tool
   • Application:3D printing/plastic
   • Pack Size:607 pcs
   • Corrosion Resistance:Oxidation/corrosion resistant
   • Additional Feature:607-piece total
   • Additional Feature:45-degree spiral knurling
   • Additional Feature:No countersinking needed

7. E-Z Lok Metric Helical Threaded Insert Kit (M16-1.5)

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   Best Metric Repair

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   E-Z LOK’s M16-1.5 kit makes metric repair easy whenever you need a strong threaded fix. It includes five 304 stainless steel inserts, an STI tap, and an installation tool, so you can restore stripped threads without hunting for extras. Use it on aluminum, cast iron, magnesium, and other soft metals whenever you want a corrosion-resistant repair that handles heat up to 800°F. Each insert measures 32 mm installed length with a 16 mm groove diameter, giving you a precise fit. The combo tang-break tool also helps you finish cleanly and quickly.

   • Thread Type:M16-1.5
   • Material:304 stainless steel
   • Kit Contents:Inserts, STI tap, install tool, tang break tool
   • Application:Soft metals
   • Pack Size:5-pack
   • Corrosion Resistance:Corrosion resistant
   • Additional Feature:M16-1.5 thread size
   • Additional Feature:32 mm installed length
   • Additional Feature:Combo tang-break tool

8. Wire Thread Repair Inserts Assortment Kit (210Pcs)

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   Most Versatile

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   This 210 piece kit is a versatile choice for repairing damaged threads. It includes seven metric sizes, from M3 to M12, each stored in its own plastic box grid for quick sorting. The 304 stainless steel inserts resist corrosion, rust, and oxidation, helping protect threads over time. Deep, high precision coils distribute load evenly, reduce pitch mismatch, and improve connection strength. They also provide elastic support against shock, impact, and wear. Use them in aviation, cars, electronics, molds, turbines, and more.

   • Thread Type:M3/M4/M5/M6/M8/M10/M12
   • Material:304 stainless steel
   • Kit Contents:Inserts assortment kit
   • Application:General repair
   • Pack Size:210 pcs
   • Corrosion Resistance:Rust/oxidation resistant
   • Additional Feature:Seven metric sizes
   • Additional Feature:Deep thread design
   • Additional Feature:Each size separate

9. M6X1.0 Thread Repair Kit with 10 Inserts

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   Best Engine Repair

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   The M6X1.0 Thread Repair Kit with 10 inserts is ideal whenever you need reliable engine repair. You get a drill, tap, installation driver, counterbore, and 10 stainless steel M6x1.0x9.4mm inserts, so you are set for a complete fix. Use it to repair damaged or stripped internal screw threads, replace worn threads, and restore holes for reuse. The solid steel inserts provide a stronger internal thread and outlast helicoil style options. Its recessed lip cutting design supports the flange and improves the repair. You can use it in automotive and general thread repair jobs.

   • Thread Type:M6x1.0
   • Material:Stainless steel
   • Kit Contents:Drill, tap, driver, counterbore, inserts
   • Application:Engine/automotive repair
   • Pack Size:10 inserts
   • Corrosion Resistance:Stainless steel durability
   • Additional Feature:Recessed lip cutting
   • Additional Feature:Counterbore included
   • Additional Feature:Solid steel insert

10. M5 x 0.8mm Helicoil Thread Inserts (80Pcs)

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    Best Vibration Resistance

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    M5 x 0.8mm Helicoil inserts are ideal when you need strong, vibration-resistant threads. You get 80 stainless steel wire inserts in an M5 x 0.8mm format, with a 15mm length and a 5mm drill hole size. Their 304 stainless steel construction resists rust, corrosion, and wear, so they hold up in demanding applications. The anti-loose design helps improve thread strength, distribute load evenly, and reduce pitch mismatch. They also absorb vibration and improve fire resistance, making them a practical choice for aircraft and other high-safety applications.

    • Thread Type:M5 x 0.8
    • Material:304 stainless steel
    • Kit Contents:Wire inserts only
    • Application:High-safety repair
    • Pack Size:80 pcs
    • Corrosion Resistance:Corrosion resistant
    • Additional Feature:3D insert length
    • Additional Feature:Anti-loose design
    • Additional Feature:Aircraft-grade suitability

Factors to Consider When Choosing Helical Threaded Inserts

When choosing helical threaded inserts, start by matching the thread size to your application and checking the base material you are repairing. You should also confirm the insert length, especially if you need extra holding power or deeper engagement. For long-term results, consider corrosion resistance, and make sure you have the right installation tool kit on hand.

Thread Size Compatibility

To get a helical threaded insert to work properly, you need to match it exactly to the damaged hole’s original thread spec, whether that is 3/8-16, M16-1.5, #12-24, or M5 x 0.8. Check the diameter and the thread pitch, because two inserts with the same nominal size can still clash if the pitch differs. You also need to verify the tapped hole or drill size before you install anything, since the prepared hole determines whether the insert seats and transfers load correctly. Match the insert’s installed length to the available depth so you can get full thread engagement without bottoming out. Finally, confirm that you are using the correct hole standard, because metric and imperial threads are not interchangeable, even when their sizes look similar.

Base Material Type

The right insert starts with the right material. You should match the insert to your parent material and environment. For metal thread repair, stainless steel is a smart pick because it resists corrosion and handles temperatures up to 800°F. If you are repairing soft metals such as aluminum, cast iron, or magnesium, choose steel or stainless steel to reinforce tapped holes and reduce stripping. In harsher heat or corrosion, 304 or 18-8 stainless steel wire inserts give you a strong balance of toughness and rust resistance. When you are working with plastic or 3D printed parts, brass threaded inserts usually perform better because they conduct heat well and grip securely when heat set. Harder materials also spread loads better than damaged base threads alone.

Insert Length Requirements

Insert length should match the depth of the repaired hole so the coil fully engages the new threads without bottoming out. You should compare the insert’s installed length with the drilled and tapped depth before you buy or install it. A longer insert gives you more thread engagement, so it usually spreads load better and helps in soft metals. A shorter insert can work in shallow holes, but you will lose some contact area for the fastener. When the insert is too long, it can stick out or interfere with assembly, so check the available space carefully. Measure the hole in millimeters or inches, then pick a length that fits cleanly. That simple check helps you avoid weak repairs and wasted effort, and it keeps your threaded connection secure.

Corrosion Resistance Level

Once you have matched the insert length to the hole depth, check how well it can resist moisture and exposure. If you expect rain, salt, chemicals, or constant humidity, choose an insert with clear corrosion resistance instead of standard carbon steel. Stainless steel options such as 304 or 18-8 are a strong choice because they resist rust and oxidation. Stainless steel wire inserts also perform well in harsher conditions and can tolerate temperatures up to 800°F. Brass heat-set inserts are another smart choice, especially when you are working with plastic and want long-term resistance to wear and oxidation. A plain, silver, or galvanized finish can add surface protection, but it will not help much if the base material cannot resist corrosion in the first place.

Installation Tool Kit

A complete installation tool kit makes helical threaded inserts much easier to install correctly because it usually includes the STI tap, an insertion tool, and often a tang break or combo install tool. You should match the kit to the insert’s thread size because metric and imperial sets are not interchangeable. A 5/8-11 kit will not fit a 3/8-16 repair. Some kits also include a drill and counterbore, which help you prepare the hole before tapping. The insertion tool winds the coil evenly into the tapped hole, so the insert seats fully and restores the internal threads accurately. When you use the right kit, you reduce cross-threading, uneven seating, and installation damage, especially on small or high-load fasteners.

Application Temperature Limits

When you choose helical threaded inserts for hot environments, check the insert’s temperature rating first. 18-8 and 304 stainless steel inserts can handle roughly 800°F, but any preapplied locking adhesive may fail at a much lower temperature. You should also confirm that your operating temperature stays within both the insert’s limit and the adhesive’s limit, if it has one. If you are installing heat set inserts in plastic, make sure the installation heat will not soften or deform the thermoplastic. For high heat service, stainless steel usually outperforms lower temperature materials by preserving thread strength and corrosion resistance. If your part will heat and cool repeatedly, choose an insert rated for thermal cycling so it resists loosening and maintains holding power longer.