How easily repair damaged threads with Helicoils

Introduction

Helicoils are a type of thread insert used to repair damaged threads in metal parts. They provide a permanent and reliable fix for stripped, damaged, or worn threads. 

A helicoil insert looks like a coiled spring with threads on the outside surface. The insert screws into a pre-tapped hole in the part, essentially creating new threads where the old threads were damaged. Once installed, the helicoil provides full thread strength and functionality, restoring the part to its original condition.

Helicoils are commonly used in automotive and machinery repair when threads become damaged from overuse, corrosion, cross-threading, or other issues. They offer a cost-effective and time-saving repair option compared to more extensive replacements or re-machining. With the proper tools, helicoils can be installed quickly to get equipment back up and running.

The main purpose of helicoils is to avoid replacing expensive parts or entire assemblies due to minor thread damage. By repairing threads with inserts, downtime and repair costs can be significantly reduced. Helicoils provide a durable and permanent fix that lasts the lifetime of the part if installed correctly.

When to Use Helicoils

Helicoil inserts are designed to repair and restore damaged or stripped threads in drilled holes. They provide a durable and permanent fix for threads that have been damaged due to wear and tear, over tightening, cross-threading, or corrosion. 

Helicoils are ideal to use when the hole is still intact and usable, but the threads have become unusable in their current state. Common examples where helicoils can save the day include:

- Engine bolt holes that have been stripped or corroded

- Holes in machineries and equipment with worn out threads 

- Stripped holes in automotive parts like cylinder heads, transmission housings, intake manifolds etc.

- Holes in firearms components like receivers and barrels that have damaged threads

The great thing about helicoil inserts is that they can repair the threads to be even stronger than the original. This allows the fasteners to be reused rather than having to replace the entire part.

Overall, if you have a hole with damaged or unusable threads, but the hole itself is still intact, a helicoil insert is likely your best option for a durable and permanent repair. The insert will restore the threads to a like-new condition or better.

Helicoil Insert Sizes

Helicoil inserts come in a wide variety of standard sizes to repair both metric and imperial threaded holes. Some of the most common sizes include:

- For metric threads, M3, M4, M5, M6, M8, M10, M12 are standard. These match metric fastener sizes.

- For imperial/UNC threads, 4-40, 6-32, 8-32, 10-24, 10-32, 1/4"-20, 1/4"-28, 5/16"-18, 5/16"-24, 3/8"-16, 3/8"-24 are readily available. These match customary bolt sizes.

- Larger sizes like M14, M16, and bigger are available as well. 

- Tiny sizes down to 2-56 threads can also be found for precision applications.

The sizing corresponds directly to the original thread that needs repair. So an M8 x 1.25 helicoil is designed to fix an M8 fastener hole, and a 1/4"-20 insert matches up with 1/4"-20 threaded holes.

It's important to carefully match the helicoil size to the existing hole, both in diameter and thread pitch, for proper installation. Most kits include a range of sizes to accommodate different fastener threads. Standardization makes it easy to identify and select the helicoil you need.

See full helicoil chart here.

Helicoil Insert Materials

Helicoil inserts come in a variety of materials to suit different applications and operating conditions. Some of the most common helicoil insert materials include:

Stainless Steel - Stainless steel is a popular choice for helicoil inserts due to its strength, corrosion resistance, and relatively low cost. Grade 303 and 316 stainless steels are commonly used. Stainless provides good performance in many general applications.

Titanium - Titanium helicoil inserts offer high strength-to-weight ratio, corrosion resistance, and biocompatibility. Grade 5 titanium is commonly used. Titanium is ideal for applications where weight savings are critical or when interacting with sensitive materials.

Inconel - Inconel is a nickel-chromium alloy that offers excellent high temperature properties up to 1000°F or more. Inconel inserts have great strength at elevated temps and good corrosion resistance. Used for high-heat engine applications.

Brass - Brass helicoils provide good corrosion resistance and are non-sparking, making them suitable for some electrical and hazardous location threads. Brass is softer and not as strong as steel.

Aluminum - Aluminum helicoil inserts are lightweight and have good corrosion resistance. Not as strong as steel but can work well in non-critical aluminum parts. 

The material selection depends on the operating temperature, strength needs, corrosion resistance, weight considerations, and other application requirements. Consulting with a fastener supplier is recommended to pick the optimal helicoil insert material.

Helicoil Insert Kits

Helicoil insert kits contain all the tools and parts needed to repair a stripped or damaged thread using helicoil inserts. A typical helicoil kit includes:

- Helicoil Tap - Used to cut new threads in the hole to match the insert. The tap diameter and thread pitch match the helicoil inserts in the kit.

- Helicoil Installation Tool - This is used to thread the helicoil insert into the prepared hole. It has a mandrel that grips the insert and guides it into the threads.

- Tang Breakoff Tool - After installation, the tangs on the insert need to be broken off. It can be done with or without a tool.

- Drill Bit - In some kits, a drill bit is included matched to the tap size for pre-drilling the hole. This reduces tap wear and makes cutting new threads easier.

- Helicoil Inserts - A assortment of inserts is included for common thread sizes. Each insert has a tang on the top end for installing and breaking off. The coils match the tap thread pitch.

- Lubricant - A tap lubricant is needed when cutting new threads prior to insert installation. This helps the tap cut smoothly.

The number of tools and inserts varies between kits. More comprehensive professional kits contain components to repair many thread sizes, while basic kits may just include common metric or inch sizes. Always ensure you have the right tap, inserts, and tools for the thread repair job.

Preparing the Damaged Threads 

Before installing a helicoil insert, it's important to properly prepare the damaged threaded hole. This involves cleaning out any debris as well as resizing the hole to the appropriate dimensions.

First, use a tap to clean out the damaged threads and any built up debris. Select a tap that matches the original thread size and run it through the full depth of the hole. This will clear out any loose material or damaged threads. Be sure to back the tap out periodically to remove the cuttings. 

Next, the hole will need to be resized to fit the specific helicoil insert being installed. Use the appropriately sized helicoil tap to cut new threads to the correct inner diameter required for the insert. Cut the full thread depth in one pass if possible, again backing the tap out periodically to clear cuttings. 

The hole is now ready for the helicoil insert. It's been cleaned of debris and resized to the proper dimensions. Properly preparing the damaged hole is crucial for allowing the insert to achieve maximum strength and load carrying capability. Rushing this step risks a poor repair. Take the time up front to tap and size the hole correctly.

Installing the Helicoil

To install the helicoil insert, follow these steps:

1. Clean out the damaged threads using a tap or die. Make sure to remove any debris or metal shavings.

2. Select the proper helicoil insert based on your thread size. Check that the insert outer diameter matches the hole size.

3. Attach the installation tool to your drill and insert the helicoil. The tangs on the insert should fit into the slots on the tool. 

4. Apply cutting oil or lubricant to the insert. This helps guide it into place and prevents overheating.

5. Keep the drill straight and slowly twist the insert into the threaded hole. Apply firm pressure but don't force it.

6. Continue threading the insert until it reaches the bottom of the hole. The tangs should break off once fully installed.

7. Use a tap to clean out any small shavings or burrs inside the newly threaded hole. 

8. Test the insert by running a bolt through it. Make sure it screws in smoothly.

9. If desired, you can stake the top 1-2 threads of the insert. This flares the helicoil and helps prevent turning.

Following these steps will result in a strong and secure helicoil repair. Take your time and use the proper technique for best results.

Removing a Helicoil

If needed later, removing a helicoil insert is a straightforward process. You'll need a few basic tools:

- A drill bit slightly larger than the inner diameter of the insert 

- An easy-out screw extractor or reverse threaded screw 

- WD-40 or another penetrating oil

Start by spraying the WD-40 or penetrating oil into the insert to help loosen it. Let it soak in for 10-15 minutes.

Then, using the drill bit larger than the inner diameter, drill into the center of the insert. This will drill away the inner coils and allow you to get down to the bottom thread of the insert. 

Take the easy-out or reverse threaded screw and thread it into the insert. Tighten it down securely and then turn counterclockwise to back the insert out. Keep turning counterclockwise until the insert is completely removed. 

Be sure to thoroughly clean out any debris left behind from the old insert. Chasing the threads with a tap will help clean them up and restore the original thread size. Then you can install a new helicoil insert if needed.

Removing a helicoil insert is usually quick and straightforward. Just take care to use the proper size drill bit and extractor tools. With a little patience, you can completely remove an insert without damaging the original threads.

Pros and Cons of Helicoils 

Helicoils offer several advantages but also have some disadvantages to consider:

Advantages of Helicoils

- Restore original thread size - Helicoils allow you to repair stripped or damaged threads and restore the original thread size. This is better than alternatives like oversized inserts.

- Reusable - Unlike one-time thread repair inserts, Helicoils can be removed and reused if needed. The coil stays intact when removed properly.

- Strong and durable - Helicoils provide a permanent and reliable thread repair solution. The coils distribute load evenly and resist vibration.

- Easy installation - With some practice, Helicoils can be installed quickly with basic tools. The tang breakoff design makes installation straightforward.

- Wide size range - Helicoil inserts are available in metric and SAE sizes ranging from M3 to M12 and 4-40 to 1/2-13. This covers most common fastener sizes.

Disadvantages of Helicoils

- Can be difficult for beginners - There is a learning curve to installing Helicoils properly. Improper technique can damage the insert or threads.

- More expensive than some alternatives - While durable, Helicoils cost more than basic thread repair inserts. The installation tool kit also adds to costs.

- Tang removal - The tang must be removed after installation, leaving a small hole in the thread. Proper tang removal technique is important.

- Thread tapping often required - For ideal results, the damaged threads should be tapped before Helicoil insertion. This adds an extra preparation step.

- Not for oversized holes - Helicoils rely on the existing hole size and do not work if the hole is damaged or stripped out.

Conclusion

Helicoils can be a great solution for repairing damaged threads in metal parts. They provide a durable and reusable thread repair that is relatively easy to install. The key steps are using the right tap to clean out and reshape the damaged thread, inserting the helicoil with the installation tool, and making sure the threads are properly aligned.

When used properly, helicoils create strong, clean internal threads that can often be even better than the original. However, they do take some skill and the right tools to install correctly. For critical applications, it's a good idea to practice first on a spare part. 

Overall, helicoil inserts are a recommended option for most common thread repair jobs. They are reusable and enable the part to be serviced multiple times. The inserts are available in many sizes and materials to match the original thread. Proper installation is important, but helicoils remain one of the most robust and reliable ways to salvage damaged threaded holes.

For automotive or machine repair projects needing thread repairs, helicoil kits provide an essential solution worth learning to use effectively. Taking the time to fully restore internal threads to like-new condition will provide long-lasting results.

See here full catalog and product datasheets of Helicoil inserts, Helicoil Taps, Installation tools for Helicoils, Thread repair Kits.

Orders online are available. All popular sizes both metric and inch are in stock