Helicoil Inserts (Inch & Metric)
Helicoil-style wire thread inserts create durable internal threads by placing a formed stainless steel coil inside a tapped hole. The insert locks into the parent material and provides a hard, wear-resistant thread for repeated assembly. Use them for original builds in softer materials or to repair stripped threads in metal parts and castings.
Why Choose Wire Thread Inserts?
- Restores or upgrades threads in aluminum, magnesium, and low-strength steels.
- High pull-out, shear, and vibration resistance with excellent wear life.
- Heat and corrosion resistance (300-series stainless standard).
- Accurate fit in standard fastener threads: UNC/UNF (inch) & coarse/fine metric.
- Available as free-running (standard) or screw-lock (prevailing torque) styles.
Common Applications
- Automotive & motorsports: engine blocks, transmission housings, brake components.
- Aerospace & defense: magnesium/aluminum structures and panels.
- Industrial machinery, pumps, molds, fixtures, and electronics enclosures.
- Maintenance & MRO thread repair where repeated assembly is expected.
Types & Options
- Free-Running: standard internal thread for smooth assembly.
- Screw-Lock: deformed coil section adds prevailing torque to resist loosening.
- Lengths: typically 1.0D, 1.5D, 2.0D, and 3.0D (insert length = D × nominal thread size).
- Materials/Finishes: 18-8/304 stainless standard; other alloys/surface treatments by spec.
Quick Install Overview
- Drill out the damaged hole to the specified diameter.
- Tap with the matching insert tap (STI tap).
- Load the insert on the tool and drive until ~½ pitch below surface.
- Break off the tang (through-hole) with a punch; or leave if using tangless style.
Tip: Use cutting fluid, keep taps square to the surface, and follow the insert chart on each product page for the correct drill size and tap pitch.
Helicoil Inserts FAQ
What’s the difference between free-running and screw-lock inserts?
Free-running inserts provide a standard class of fit for smooth assembly. Screw-lock inserts include one or more deformed coils that add prevailing torque to resist fastener loosening under vibration.
How do I choose insert length (1.0D, 1.5D, 2.0D)?
Match length to the engaged thread depth you need. 1.0D suits most repairs, 1.5D–2.0D is preferred in softer materials or when higher pull-out strength is required.
Do I need a special tap?
Yes—use an STI (Screw Thread Insert) tap for the external insert thread. Standard UNC/UNF/metric taps won’t fit the insert properly.
Will wire inserts work in aluminum or magnesium?
Absolutely. They are commonly used to reinforce soft alloys and provide a hard, wear-resistant internal thread with improved load distribution.
How strong are the repaired threads?
Properly installed, wire inserts typically meet or exceed the strength of the original parent material by spreading load across the coil, improving pull-out and wear resistance.
Can I reuse the insert after disassembly?
Yes. Free-running inserts are designed for repeated assembly. Screw-lock types also allow reuse, though prevailing torque will feel higher on each cycle.
What drill size should I use?
Use the drill listed in the insert’s specification chart (varies by thread size and series). Always follow the size on the product page or kit instruction sheet.
Are there metric and inch options?
Yes—choose UNC/UNF for inch threads or coarse/fine metric for metric threads. Keep systems consistent with the mating fastener.
When should I pick screw-lock vs. threadlocker?
Use screw-lock when you want built-in prevailing torque from the insert itself. Use a free-running insert with liquid threadlocker when chemical locking is preferred or the joint is service-removable.
Do I have to break the tang?
For through-holes, yes—remove the tang after installation. In blind holes, use tangless inserts or a dedicated tang-removal tool to avoid bottoming damage.
What tools do I need to get started?
A drill (with the specified bit), STI tap, installation tool, and tang break-off punch (or tangless tool). Our thread repair kits package these for the size selected.