1. Typical Tapping Challenges in Tooling Shops

In Pakistani mould, jig and fixture shops, blind-hole tapping is both critical and risky. Especially in tool steels and pre-hardened steels, many operators still use a single straight flute tap “all the way down” without separating operations. This leads to:

• Chips packing at the bottom of the blind hole;

• High local load on cutting edges, causing chipping and breakage;

• Broken taps stuck in the part, forcing complete scrap of the workpiece.

2. Technical Root Causes of Blind-Hole Failures

Three technical factors usually overlap:

1. Poor chip evacuation: Straight flute taps are more suitable for through holes; in blind holes, chips can only be pushed forward and pack at the bottom.

2. Uncontrolled torque: Without torque monitoring, any sudden increase near the bottom or in hard spots leads to instant failure.

3. Misuse or omission of 3-piece sets: Many shops only use a “plug tap” or “bottom tap”, ignoring the role of a taper tap in step-wise cutting.

3. Solution: Step Cutting + Unified Standard

Although ISO529 straight flute taps are naturally better for through holes, they can still be used in short blind holes or softer steels, provided that step cutting and chip evacuation are managed correctly:

• Use the full ISO529 3-piece tap set: taper tap for alignment and most of the thread, second tap for forming, and bottoming tap only where full thread depth is absolutely required;

• Enforce a “cut 1–2 turns, then back off to break chips” rhythm to prevent chip packing at the bottom;

• For deeper blind holes or harder materials, switch to spiral flute machine taps but keep the thread standard within the same ISO system.

4. Key Specification Snapshot

By standardizing tools and properly using all three taps in the set, tool shops can significantly reduce tap breakage and scrap without dramatically increasing tool costs.

5. Conclusion

For Pakistani toolmakers, avoiding broken taps in blind holes requires more than operator experience. Building the process around an ISO529 3-piece straight flute tap set, combined with step cutting, controlled chip evacuation and appropriate tool changes for deep blind holes, offers a practical path to lower failure rates and higher reliability.