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Helicoil Thread Repair Kit–Pros and Cons

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Repairing your thread can be addressed by relying on a Helicoil thread repair kit. Helicoil is one of the most reliable tools out there for thread repair. Although it has been around for a long time and many products have come to the market, it can still be used for repairing internal threads successfully. However, repairing with Helicoil also takes specific steps that might take a while to perfect.

At the end, we present you with another option and explain why adopting a versatile option is more convenient, economical, and reliable as well.

Repairing Threads with Helicoil

Helicoil is a coiled wire insert that is used to repair an internal thread to its original diameter and pitch. You have to insert it using an installer, but before that you have to make sure that you have the right specifications. 

  • Right Helicoil length
  • Right diameter

The above-mentioned aspects are just two things that will tell you if you are using the right Helicoil. 

Make sure to have the right length, because you don’t want the trouble of doubling up a Helicoil to get to your target length. A Helicoil has a tang at the end, and you have to be creative to remove the tang on the second Helicoil before setting it after the first one. The tang actually reduces the torque on the Helicoil, so removing the tang before fully inserting the coil is not advisable. Although its manufacturer actually produced tangless inserts, these may be hard to find in the market. Secondly, the two coils might not line up perfectly with each other. 

Take note, you would be drilling and then tapping into the hole. This is where it might be difficult at first. For experienced mechanics, this is a skill that is easy to pick up. Tapping must be done by being square and perpendicular to the hole. Otherwise, you run the risk of misaligning the threads. 

Helicoil set (Drillbit, STI or Screw Thread Insert Tap, Helicoil insert). 

Installing the Coil

Helicoil Thread Repair Kit–Pros and Cons
Helicoil Insert

Because you have to insert a coil, you will be drilling into the hole to get a slightly larger size. Inserting the Helicoil requires the following steps.

  1. Use drillbit to drill a slightly larger hole
  2. Tap into the hole to form the grooves for the coil insert. The tap you will use is provided in a kit. This is a special tap called STI, which has a slightly larger diameter than an ordinary tap to accommodate the coil insert. Ensure to be perpendicular to the workpiece for proper installation.
  3. Insert the coil using the handle of the tap
    1. If you have a coarse pitch thread, directly use the installation tool to secure the insert in the tapped hole
    2. If you have a fine pitch thread, you must use a pre-coil body which will compress the threads of the coil prior to insertion to the tapped hole. Usually, this goes with the thread kit.

Helicoil Pre-coil body for fine threads

  1. Remove the tang with a punch by hitting it with a hammer

It should be noted that some would use a cheaper alternative, but this is not advisable. If you use a cheaper alternative, there are instances when the tang might clamp the tool and make it difficult to remove the tool. 

It is also advisable to follow a rule of thumb when using a Helicoil thread repair kit. When installing, make sure to keep the top of the insert ¾ to 1 turn below from where the tapped thread first made its way into the hole. This would make sure that the Helicoil is snug tightly into the hole.

Pros and Cons of Helicoil

Pros

  • Helicoils are specially designed on the outer layer to grip the wall of the hole. 
  • It has a variety of designs that can work well with different thread types and configurations. 
  • Available in several lengths
  • Proven to be reliable since 1930s–used by military as well
  • Available in kit with all the tools needed
  • Available also for high duress applications, such as well drilling, gas turbines, water applications and vacuum environments
  • Available in corrosion resistant design

Cons

  • Complex set of steps that require professional skills
  • Requires different sizes for different hole diameters
  • Can only fix the internal threads
  • Requires different installation for coarse or fine threads

An Economical Option over Coiled Inserts

Helicoil Thread Repair Kit–Pros and Cons

Despite what appears to be an easy operation as shown in videos, inserting Helicoils takes some skills. There are some factors to consider that make it challenging. 

One, it’s plausible that you have to re-do it if you incorrectly installed the coil, if not ruin the project entirely. Secondly, as Helicoils are inserts with specifications, you would need a different kit for every different internal thread to be repaired. That would mean a different tap size (STI), and a different drill bit size, too. 

To make it more economical, we can use an economical option instead. A much simpler way to fix an internal thread is to use Rotary thread

Instead of installing by way of drilling, tapping, and inserting, you would need to just use a drill or a Dremel instead–but with some cutting techniques. Rotary thread can be used on different threads for repair, and can fix every kind of inch, metric, and pipe. You can use it for internal and external threads, too. Using this simple tool by attaching it to a Dremel or a drill, it would only take a few seconds to a couple of minutes to repair dented, corroded, and hardened threads. 

Another reason to use it is that you can keep it in a handy area, whether in your toolkit or together with small tools you have in your garage. It’s as simple as plugging in your drill and starting the repair work. 

For DIY enthusiasts, it’s an easy skill to learn, and also intuitive to use. For businesses, it would save you days by directly repairing a thread, rather than waiting for a specific Helicoil thread repair kit to arrive from the store.

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