Have you ever faced the frustration of tap machining failures? I know I have. In the world of CNC machining, particularly at Santanoo CNC Machining Service, addressing these failures is crucial for delivering high precision and quality products.
Tap machining failures are not just a nuisance but a significant bottleneck in manufacturing. From oversize to undersize pitch diameters, breakage, chipping, jagged threads, to galling – each failure has its own set of challenges and solutions.
Selection of chip removal groove type of taps
As shown in the figure below, the chip removal groove type of tap is mainly divided into straight groove type, spiral groove type, apex spiral groove type.
Hand Tap
Wide range of applications for all types of holes and hole depths.
Spiral Fluted Tap
Spiral fluted taps are the most common type of tap, where chips are discharged upwards along the tap, and are mainly used for threading blind holes.
Spiral Pointed Taps
The most powerful type of tap, chips are discharged down the tap, which is the opposite of a spiral fluted tap, and is suitable for machining through-hole threads, not blind holes.
Tap machining of common faults and solutions
Oversize Pitch Diameter
Oversized pitch diameters often result from incorrect tap selection or machine settings. This issue can lead to weak threads that compromise the integrity of the part.
To tackle this, we at Santanoo ensure meticulous calibration of our machines and use high-quality taps.
Causal analysis
1.Incorrect tap selection
Solution:
- Select tap of appropriate limit.
- Increase chamfer length.
- Select con-eccentric relief tap.
2.Chip packing
Solution:
- Reduce number of flutes to provide extra chip room.
- Select tap with oil hole.
- Make drill hole diameter as large as possible.
- In the case of blind holes, make it as deep as possible.
- Change lubricant type and lubricating method.
3.Incorrect operating conditions
Solution:
- Use floating type tap holder.
- Avoid runout of spindle.
- Adjust machine capacity (drive force) to appropriate level.
- Adjust tapping speed to appropriate level.
- Adjust feed speed to appropriate level to prevent torn or rough thread.
- Use forced feed (lead feed) tapper.
- Prevent misalignment with drill hole.
- Chamfer entrance of the drilled hole.
4.Welding
Solution:
- Select surface-treatment (steam oxide or coating).
- Select tap with oil hole.
- Reduce tapping speed.
- Replace lubricant with one that has higher anti-galling properties.
Undersize Pitch Diameter
Undersize pitch diameters are equally problematic, often caused by excessive wear or incorrect tap geometry.
Our approach involves regular tool inspection and using taps with optimal geometry for specific materials. Learn more about our precision techniques.
Causal analysis
1.Incorrect tap selection
Solution:
- Select oversize tap.
- Tapping material: Materials with low over size margin, such as copper alloy, aluminum alloy and cast iron
- Shape of tapping material: Hollow materials and mild sheet steels with punched holes which have “”a spring back”” action after tapping
2.Damaged internal thread
- Adjust reverse speed to an appropriate level, to avoid damage at entrance of tapped thread on the way out of the hole.
Breakage
Breakage is a nightmare in tap machining. It’s usually due to excessive feed rate, insufficient lubrication, or material hardness.
To prevent this, we employ state-of-the-art lubrication systems and adjust feed rates based on material properties. Find out how we do it in our article.
1.Chip packing
Solution:
- Make hole for blind hole as deep as possible.
- Correct inclination of drilled hole.
- Remove chips collected in drilled hole and around tapping areas in previous process.
- Keep space for removal of chips.
2.Excessive tapping torque
Solution:
- Select tap with long chamfer length.
3.Incorrect operating conditions
Solution:
- Avoid inconsistent feed rate
- Use a tap holder that has torque adjustment function.
- Use a floating type tap holder.
- Reduce tapping speed.
- Avoid misalignment between tap and drilled hole as well as inclination of drilled hole.
- Avoid hitting bottom of the drilled hole with tap.
- Avoid misalignment and inclination from drilled hole.
- Avoid work hardening of the hole after tapping.
- Remove chips genera
- Pay special attention to changes and variations in tapping material, hardness and structure.
Chipping
Chipping, often a result of brittle taps or misalignment, can ruin the finish of your product.
We counter this by using taps made from resilient materials and ensuring perfect alignment in our setups.
1.Incorrect tap selection
Solution:
- Prevent chip clogging
2.Incorrect operating conditions
Solution:
- Avoid inconsistent feed rate
- When tapping hole, do not reverse rotation suddenly.
- Use floating type tap holder.
- Reduce tapping speed.
- Avoid misalignment between tap and drilled hole as well as inclination of drilled hole.
- Use lubricant that has higher anti-galling properies.
- Avoid misalignment and inclination from drilled hole.
- Avoid work hardening of the hole after tapping.
- Pay special attention to changes and variations in tapping material, hardness and structure.
Jagged Thread
Jagged threads are typically due to irregular feed or speed. This defect can affect thread functionality significantly.
At Santanoo, precise control of feed and speed is our mantra. We’ve shared some of our secrets in this resource.
1.Incorrect tap selection
Solution:
- Use a floating type tap holder.
- Avoid runout of spindle.
- Reduce tapping speed.
- Hold work material more securely.
- Pay special attention to thickness of work material.
- Review lubricant type and lubricating method.
Galling
Galling, the unwanted welding of surfaces, is often a challenge with certain materials.
Using specialized lubricants and selecting the right materials are key to avoiding this. More on our approach can be found below.
1.Excessivefrictional heat
Solution:
- Reduce tapping speed.
- Review lubricant type and lubricating method.
- Correct lubricant change/replenishment intervals.
- Prevent entry of other oils such as operating oil.
- Filtrate oil stored in tank.
Technical Insights
In the field of CNC machining, understanding the nuances of each failure type is essential. We constantly innovate and adapt our methods to ensure the highest standards.
Conclusion
In conclusion, navigating through tap machining failures requires expertise, precision, and a commitment to quality. At Santanoo, we’re dedicated to mastering these challenges, ensuring that our clients always receive the best in CNC machining
