Tap breakage is the most disliked issue that everybody wants to avoid when machining. Understanding which type of tap to use is critical to achieving the best machining results and observing some simple rules can help preventing the issue.

Where possible, the use of spiral pointed tap is the best option to achieve reliable results in machining through holes: Yamawa spiral pointed taps are rarely affected by cutting edge chipping or tool breakage problems because their geometry is especially designed to push the chips forward ahead of the feeding direction. If issues happen, it means that the flow of the chip outside of the bored hole is not smooth enough, causing the entanglement of the chips.

A spiral pointed tap has 5 thread cutting chamfer and must be fed completely through the work material to cut an acceptable thread. If the chips are not completely separated from the work material, they get caught in the tap on the reverse rotation and the chipping of cutting edge occurs.

Spiral pointed taps
Spiral pointed taps push chips forward ahead of the tap without any problem

Try to lengthen the feed stroke by three additional threads to ensure that the cutting chamfer is completely clear of the bored hole. Furthermore, if the chips produced from a spiral pointed tap hit the bottom of the jig or you allow the chips accumulate, additional chips won’t discharge well and problems like chipping of the cutting edge and/or tool breakage will occur.

To sum up, here two simple rules to avoid chipping/breakage of the tool when tapping through holes:

  • Make sure that the cutting chamfer of the tool is tapping beyond the end of the part to be machined
  • Make sure there is enough space at the end of the bored hole to eject the chips smoothly