Solving the Problem of Broken Screw Tails with Imported Taps: A Practical Maintenance Guid

Given the high cost of imported taps, implementing reasonable repair solutions when faced with broken screw tails can significantly reduce costs and restore production. This article details repair methods for varying severities of tail breakage, helping you resolve the issue effectively while controlling expenses.

Problem Phenomenon: Excessive rake angle of the tap leads to noticeable screw tail breakage.

1. Select Appropriate Tools: Use a professional diamond file, which has high hardness and is less likely to damage the tap surface.
2. Adjust Rake Angle Height: Gently file along the direction of the tap's rake angle to reduce the height to an appropriate range.
3. Enhance Anti-Slip Function: Roll non-slip teeth into the adjusted area to increase friction and prevent recurring breakage.
4. Verify Repair Effect: Conduct a trial pressing after each adjustment. Observe if the breakage improves, and repeat adjustments if necessary.

Problem Phenomenon: Slight tail breakage requiring investigation into potential root causes.

1. Insufficient Thread Groove Opening
   • Solution: Use a triangular diamond file to slightly widen the thread groove along its direction, ensuring the screw tail passes through smoothly.
2. Mismatched Rake Angle Height
   • Solution: Precisely adjust the rake angle using a diamond file to achieve a perfect match with the screw tail.
3. Weakened Non-Slip Teeth Function
   • Solution: Grind a punch into a flat "-" shape on a grinding wheel and use it to deepen the non-slip teeth, enhancing grip.

Problem Phenomenon: Breakage unrelated to the tap itself, caused by external factors.

1. Excessively Hard Wire Material
   • Switch to softer wire material, or perform annealing treatment on the existing wire to reduce its hardness.
2. Improper Screw Dimensions
   • Adjust the photoelectric marking length to avoid excessive screw tail length that causes stress concentration.
3. Mismatched Process Parameters
   • Thoroughly check thread rolling speed, pressure, and other parameters to ensure they are compatible with the tap characteristics.

When performing repairs, pay special attention to the following points:

• Protect Tap Structure: Always avoid the tap's cutting edge area during maintenance to prevent structural damage that could scrap the tap.
• Maintain Length Consistency: After adjustment, ensure the lengths of the long and short sections of the tap are equal to prevent screw forming deviations.
• Follow the Slope Direction: Perform adjustments along the direction of the tap's tail slope, maintaining a smooth surface to reduce stress concentration points.
• Apply Gradual Adjustments: Adhere to the principle of "small amounts, multiple times." Conduct a trial pressing after each adjustment to avoid over-correction.

When repair costs approach or exceed the price of a new tap, consider the following alternatives:

1. Localized Precision Repair
   • Use an oilstone to lightly polish the broken tail area, rounding its edges to reduce the risk of breakage (suitable for minor breakage).
2. Custom Professional Taps
   • Commission new, high-precision taps to ensure long-term stability and production efficiency.
3. Optimize Production Process
   • Adjust thread rolling machine parameters, such as optimizing the feed chamfer and grinder feed ratio, to reduce stress on the tap.

• Priority Repair Scenarios: When breakage is caused by tap rake angle, thread groove, or non-slip teeth issues, professional filing adjustments can usually resolve it effectively.
• Comprehensive Investigation of External Factors: If the breakage is related to wire material characteristics or process parameters, adjust the materials or production process accordingly.
• Structural Protection Principle: Always protect the core structure of the tap during maintenance, maintain component consistency, and avoid over-adjustment.
• Cost-Benefit Assessment: When repair costs reach 50%-70% of the price of a new tap, consider ordering a new tap to ensure production quality and long-term stability.