Tap breakage is one of the most critical issues in cut tapping. It not only interrupts production but can also damage the workpiece, require the broken tap fragment to be removed, and result in significant costs due to scrap, rework, and machine downtime. Understanding why a tap breaks is essential to preventing the problem and ensuring a stable, repeatable process.

In this guide, we examine the most common causes of tap breakage, the warning signs that precede it, and the most effective technical solutions, with particular attention to UFS geometries and technologies.

Tap breakage during cut tapping: troubleshooting UFS

Why the tap breaks: a technical overview

A tap breaking is almost always the result of torsional overload or a sudden tool jam during machining. This happens when the chip is not evacuated properly, when the tap isn't aligned with the hole, or when the parameters and tool aren't suitable for the material.

Signs that indicate a tap is about to break

  • sudden increase in cutting torque;
  • chip that is compacted or doesn't come out of the flutes;
  • vibrations or unusual noises during tapping;
  • tap that “sticks” in blind holes;
  • changes in thread quality before breaking.

 Main causes of tap breakage

The most common technical causes include:

  • Chip clogging: when the chip isn’t cleared, it packs into the flutes and jams the tool.
  • Tap–hole misalignment: even small coaxiality errors create side loads that can cause breakage.
  • Bottom-of-hole collision: common in blind holes with insufficient depth or improperly set cycles.
  • Wrong tap choice: geometry, chamfer, or coating not suited to the material or type of hole.
  • Machines with play or unsuitable spindles: lack of rigidity increases alternating loads and shortens tool life.

UFS solutions to prevent tap breakage

To drastically reduce the risk of breakage, it's necessary to work on the tool, parameters, and machine system. The most effective solutions include:

  • Use taps with a central hole (FOR versions), which allow internal lubrication and improve chip removal.
  • Avoid machines with play in the axes or spindle, as this compromises alignment.
  • Slow down the cutting speed if you see signs of stress or compact chips.
  • Use floating chucks, chosen based on the type of tap and application.
  • Pick the right geometry depending on the material and type of hole (blind, through, deep).

Best practices for safe and stable threading

  • monitor the shape of the chip during machining;
  • check the useful depth of the hole before tapping;
  • regularly check the tap for wear;
  • make sure the spindle is suitable for the type of tap;
  • prefer internal lubrication when working in deep blind holes. Tap breakage isn’t inevitable: with the right choice of tool, proper geometry, and careful control of process parameters, you can get stable, repeatable tapping without machine stoppages.