Troubleshooting
Tapping is a complex process and often the last machining operation performed on the workpiece. Therefore, incorrect or faulty tapping can compromise the quality of the entire workpiece. Numerous factors influence the process: cutting parameters, drilling parameters, lubrication, machine conditions. The choice of the correct tool is paramount in order to obtain high quality threads. The following table summarises the most common problems encountered during tapping and their possible solutions.
Chipped teeth on tap
- Choose correct tap, with lower rake angle or longer chamfer.
- Reduce cutting speed.
- Check drilled hole size is not too small.
- Check tap alignment and run-out of tap on tapping attachment.
- For deep blind holes (≥ 2,5xD) use taps with back-tapering.
Excessive tap wear
- Improve quality (richer emulsion, neat oil) and quantity (higher pressure) of lubrication.
- Use correct tap, with more relief or longer chamfer if possible.
- Choose coating suitable for specific application.
- Use recommended cutting parameters for specific application.
Chips clogging flutes
- Use tap with lower spiral flute angle.
- Choose correct tap with suitable rake angle and relief for specific application.
- Use tap with sharp cutting edge (bright tap or vapourised tap).
Poor finish on threaded workpiece
- Check wear on tap. If necessary, resharpen or change tap.
- Improve quality and quantity of lubrication.
- Choose correct tap with suitable rake angle and relief for specific application.
- Use recommended cutting parameters for specific application.
Built-up-edge
- Choose correct tap with lower rake angle and/or higher relief.
- Choose coating suitable for specific application.
- Increase cutting speed.
- Improve quality and quantity of lubrication.
Tap sticking
- Choose correct tap with lower rake angle and/or higher relief.
- Choose coating suitable for specific application.
- Increase cutting speed.
- Improve quality and quantity of lubrication.
Crater wear
- Choose suitable tap, with base material in HSSE-PM.
- Use coated tap.
- Improve quality and quantity of lubrication.
Tap breakage
- Check drilled hole size.
- Check alignment between tap and drilled hole.
- Reduce cutting speed.
- On blind holes, check that tapping depth is less than hole depth.
- Use tapping attachment with slip clutch.
- Use compensated tapping attachment.
Oversized thread
- Check tap tolerance is compatible with requested workpiece (nut) tolerance.
- Choose correct tap with suitable rake angle and relief for specific application.
- Reduce feed rate (revs x pitch) or use rigid / synchronous tapping attachment.
- Reduce cutting speed.
- Check tap alignment and that workpiece is fastened steadily.
- Remove clogged chips from flutes.
Undersized thread
- Check drilled hole size is not too small.
- Check tap tolerance is compatible with requested workpiece (nut) tolerance.
- Use coated tap to avoid tap sticking.
- On forming taps, use slightly larger drilled hole size.
- Check wear on tap. If necessary, resharpen or change tap.
- Choose correct tap with higher rake angle and relief.
- Use rigid / synchronous tapping attachment.
- Improve quality and quantity of lubrication.
Excessive power requirement
- On high strength materials, increase drilled hole size.
- Check wear on tap. If necessary, resharpen or change tap.
- Choose correct tap with higher rake angle and relief.
- Improve quality and quantity of lubrication.
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