Thread Repair

Thread Repairing is a common process when a thread may become damaged. This guide will investigate some of the various ways of how a thread could become damaged, a step-by-step process on how they can then be repaired, the tools required for the repair and an explanation of what is thread repairing.

RUKO Thread Repairing Process

What is Thread Repairing?

Quite simply, Thread Repairing is the re-threading of holes that have become damaged or worn and require replacing. Using Thread Repair Assortment Sets/Kits or individual Thread Repair Tools (and other drilling/cutting Tools), a user can swiftly and smoothly restore a destructed tapping hole.

Thread Repair

Undertaking a Thread Repair is a very simple straightforward task, especially if you understand the process of Thread Cutting. You can learn more about Thread Cutting in our other helpful guides shown in the “Recommended Articles” section at the bottom of this guide.

Thread Repairing can be achieved in 5 simple steps. The process requires you to drill/recreate a new hole based within the former damaged thread. Following on from that will be the insertion of a new thread in its place. Keep reading below for the full step-by-step demonstrational guide and a list of all the tools and products required for this project.


What causes a Thread to become damaged?

There are various reasons why a thread may become damaged. Typically, damage can be caused by wear and tear overtime, corrosion and too high tightening torque used when creating the thread.


What Tools do I need to undertake a repair?


For the Thread Repair Process, you will require the following:

RUKO ProCoil Thread Repair Kit
  • Jobber Twist Drill Bit
  • Single-Cut Tap (preferably Hand Tap)
  • Tap Wrench (if using Hand Tap)
  • Fitting Tool
  • Thread Insert
  • Pin-Breaker

Other Tools that could be used, include:

  • Machine Tap (instead of Hand Tap)
  • Drilling Machine
  • Cutting Oil or Lubricant

Quality Tools UK offers a complete set of RUKO ProCoil Thread Repair Assortment Kit, providing all the tools necessary for this job. Check it out here.


Or view our full Tap & Die Range of Products for Thread Cutting and Thread Repair Projects here.


Panther PPE Recommendation - RUKO UK Safety Range

We also advise on ensuring high quality safety equipment is used throughout the process.

Quality Tools UK supplies Eyewear Protection like Goggles and Specs as well as Hand Protection with a variety of different Gloves and Gauntlets. You can view our Panther PPE range here.


Thread Repair Steps:


  1. Using a single Jobber Twist Drill Bit, drill the damaged thread. Make sure the drill diameter of the Twist Drill Bit matches the same size diameter of the thread. For example, a Thread Diameter of M8 would need to match the core hole of a Twist Drill Bit of 6.8mm.

    Click/Tap this link for a table overview of different Core Hole Diameters here.


  1. Now, using a single-cut Tap, cut a new thread in replace of the old, damaged thread. We recommend using the Hand Tap and doing this process by hand. Attach a Hand Tap to a Tap Wrench and rotate to create the cut within the drilled hole. For more instructions on this, see our guide on Thread Cutting by Hand here.

    Alternatively, this process could be done by Machine using a Machine Tap. For guidance on Thread Cutting by Machine Click/Tap here. However, this is NOT recommended.


  1. The Thread can now be inserted into the newly formed hole. This should be done using a Fitting Tool. The transverse part in the middle of the thread insert, also known as the pin, should sit down in the groove opening in order for the thread to be inserted correctly.

    Whilst only applying slight pressure, turn the thread in the thread direction.

    PLEASE NOTE – Turning the thread the wrong way, against the direction of rotation could result in breakage of the pin prematurely.



  1. Once the thread has been fully inserted into the drilled hole, the pin can now be broken. Crack the pin of the thread insert with the pin-breaker at the bottom of the thread.


  1. The thread repair is now complete and the new thread is ready to use!



In the event of a thread being destroyed by corrosion, high tightening torque or wear and tear, the steps and tools stated can help to revive, fix and recreate a new Thread.


Recommended Articles:

Check out our guides to Thread Cutting below!

Thread Cutting by Hand Thread Cutting by Machine


You can contact Quality Tools UK Monday – Thursday from 8:30am - 5:00pm and Friday from 8:30am – 3:00pm, by Phone on 01299 269 501 or by Email at

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