As an important structure commonly found in mechanical parts, internal hole threads, including threads of thread
plug gauges, may be damaged due to various reasons during use. This article will delve into the tips of internal
thread repair, share common problems and solutions, and help to repair internal thread damage with ease.
Ⅰ、common cause of damage to internal threads
1. Excessive use or improper operation: Long-term use or frequent disassembly and assembly
may cause thread wear or deformation.
2. Material Defects: Raw material quality problems or processing defects may lead to insufficient thread strength.
3. Corrosion or Oxidation: When used in harsh environments, it may cause thread corrosion or oxidation.
4. Mechanical damage: Improper handling during installation or disassembly may cause mechanical damage
to the threads.
Ⅱ、Preparation for the repair of threads in the inner hole
1. Assess the extent of the damage: Carefully inspect the scope and nature of the thread damage
to determine if it can be repaired.
2. Choose the right repair method: Depending on the degree of damage and the type of thread,
choose the most suitable repair technique.
3. Prepare the necessary tools: According to the selected repair method, prepare the corresponding tools
and materials, such as thread repair taps, thread repair kits, etc.
4. Clean up the work area: Ensure that the working environment is clean and tidy to avoid impurities affecting
the quality of restoration.
Ⅲ、Common internal hole thread repair methods
1. Thread tapping method
Use: Suitable for badly damaged or excessively worn bore threads.
Procedure: Select a thread tap with the same specification as the original thread. Insert the tap vertically into
the screw hole and rotate slowly to tap. Reverse the tap regularly to remove metal shavings. When you're done,
use compressed air or a brush to clean the screw holes.
2. Threaded repair casing method
Use: Suitable for badly damaged or excessively worn bore threads.
Procedure: Select the appropriate threaded repair sleeve. A dedicated drill bit is used to enlarge the original
screw hole. Use a special tap to tap a new thread for the enlarged screw hole. Install the repair sleeve into
the newly tapped thread. If necessary, use a special tool to secure the cannula.
3. Thread filling repair method
Use: Suitable for locally damaged or missing bore threads.
Procedure: Clean the damaged area and remove oil and debris. Choose the right metal filler
(e.g., epoxy metal restorative). Mix and fill the damaged area according to the product instructions.
Once the filler has cured, the threads are re-tapped.
Ⅳ、Precautions for repairing threads in internal holes
1. Accurate measurement: Accurately measure the specifications of the original thread before repair,
and ensure that the correct repair tool is selected.
2. Keep it vertical: Whether you are tapping or installing a repair sleeve, make sure that the tool is perpendicular
to the axis of the screw hole.
3. Control the strength: During the repair process, the appropriate force should be controlled to avoid
secondary damage.
4. Regular inspection: During the repair process, the progress should be checked regularly to ensure
5. Cleaning: After the repair is complete, thoroughly remove debris and residue from the screw hole，
the quality of the repair.
Ⅴ、Quality inspection of internal hole threads after repair
1. Visual inspection: Check whether the repaired thread is complete and uniform.
2. Tactile inspection: touch the thread with your finger to see if it is smooth and burr-free.
3. Assembly test: use the bolts of the corresponding specifications for trial assembly to check
whether the fit is tight.
4. Thread gauge inspection: Use the thread gauge to check whether the repaired thread meets the standard.
5. Strength test: Torque test is carried out if necessary to ensure that the strength of the repaired
thread meets the standard.
