Tapping Troubleshooting Chart

Dimensional Accuracy

Problem	Solution
Oversize Pitch Diameter
Incorrect tap	1. Use proper GH limits of taps.
	2. Use longer chamfered taps

Chip packing	1. Use spiral point or spiral fluted taps.
	2. Reduce number of flutes to provide extra chip room.
	3. Use larger hole size.
	4. If tapping a blind hole, allow deeper holes where applicable or shorten the thread length of the parts.
	5. Use proper lubricant.

Galling	1. Apply proper surface treatment such as steam oxide or TiN.
	2. Use proper cutting lubricant.
	3. Reduce tapping speed.
	4. Use proper cutting angle in accordance with material being tapped.
	5. Use larger hole size.

Operating conditions	1. Apply proper tapping speed.
	2. Correct alignment of tap and drilled hole.
	3. Use proper tapping speed to avoid torn or rough threads.
	4. Use lead screw tapper.
	5. Use proper tapping machine with suitable power.
	6. Avoid misalignment of the tap and drilled hole from loose spindle or worn holder.

Tool conditions	1. Obtain proper indexing angle for the flutes at the cutting edge.
	2. Grind proper cutting angle and chamfer angle.
	3. Avoid too narrow a land width.
	4. Remove burrs from regrinding.

Problem	Solution
Oversize Internal Diameter
Hole size	1. Use minimum hole size.
	2. Avoid tapered hole.
	3. Use proper chamfered taps.

Galling	1. Apply proper surface treatment such as steam oxide or TiN.
	2. Use proper cutting lubricant.
	3. Reduce tapping speed.
	4. Use proper cutting angle in accordance with material being tapped.

Problem	Solution
Undersize Pitch Diameter
Incorrect tap	1. Use oversize taps for cutting materials such as copper alloy, aluminum alloy, and cast iron.
	2. Use oversize taps for cutting tubing which will have "spring back" action after tapping.
	3. Apply proper chamfer angle.
	4. Increase cutting angle.

Damaged thread	Use proper reversing speed to avoid damaging tapped thread on the way out of the hole.

Left-over chips	1. Increase cutting performance to avoid any left over chips in the hole.
	2. Remove left over chips from the hole for gage checking.

Problem	Solution
Undersize Internal Diameter
Hole diameter	Use maximum drill size.

Problem	Solution
Torn / Rough Thread
Chamfer too short	Increase chamfer length.

Wrong cutting angle	Apply proper cutting angle.

Galling	1. Use thread relieved taps.
	2. Reduce land width.
	3. Apply surface treatment such as steam oxide or TiN.
	4. Use proper cutting lubricant.
	5. Reduce tapping speed.
	6. Use larger hole size.
	7. Obtain proper alignment between tap and work.

Chip packing	1. Use spiral pointed or spiral fluted taps.
	2. Use larger drill size.

Problem	Solution
Chattering on Tapped Thread
Too free cutting	1. Reduce cutting angle.
	2. Reduce amount of thread relief.

Tool conditions	1. Avoid too narrow a land.
	2. Do not grind the bottom of the flute.

Problem	Solution
Breakage
Incorrect tap selection	1. Avoid chip packing in the flutes or the bottom of the hole. Use spiral pointed or spiral fluted taps or fluteless taps.
	2. Apply correct surface treatment such as steam oxide or TiN.

Excessive tapping torque	1. Use larger drill size.
	2. Try to shorten thread length.
	3. Increase cutting angle.
	4. Use a tap with more thread relief and reduced land width.
	5. Use spiral pointed or spiral fluted taps.

Operating conditions	1. Reduce tapping speed.
	2. Avoid misalignment between tap and the hole and tapered hole.
	3. Use floating type of tapping holder.
	4. Use tapping holder with torque adjustment.
	5. Avoid hitting bottom of the hole with tap.

Tool conditions	1. Do not grind the bottom of the flute.
	2. Avoid too narrow a land width.
	3. Remove all worn sections when regrinding the flutes.
	4. Regrind tool more frequently.

Problem	Solution
Chipping
Incorrect tap selection	1. Reduce cutting angle.
	2. Use different kind of high-speed steel tap.
	3. Reduce hardness of the tap.
	4. Increase chamfer length.
	5. Avoid chip packing in the flutes or in the bottom of the hole by using spiral fluted or spiral pointed taps.

Operating conditions	1. Reduce tapping speed.
	2. Avoid misalignment between tap and hole.
	3. Avoid sudden return of reverse in blind hole tapping.
	4. Avoid galling.
	5. Use large hole size.

Problem	Solution
Wear
Incorrect tap selection	1. Use specially designed taps for tapping heat treated material.
	2. Change to a type of high-speed steel tap that contains vanadium.
	3. Apply special surface treatment such as steam oxide or TiN.
	4. Increase chamfer length.

Operating conditions	1. Reduce tapping speed.
	2. Apply proper cutting lubricants.
	3. Avoid work hardening.
	4. Use larger hole size.

Tool conditions	1. Grind proper cutting angle.
	2. Avoid hardness reduction from grinding process.

Before you tap

Most tap failures start in the pilot hole and end with a seized flute. Get the hole right, then keep the tap cutting.