In daily drilling operations, even experienced operators frequently encounter recurring problems. Whether it is abnormal drill breakage, premature tool wear, poor chip handling, or oversized hole diameters, these challenges not only affect machining efficiency but also directly impact product quality and production costs. Systematic analysis reveals that these issues often share common technical root causes. This article examines the most frequent problems in drilling, analyzes their origins, and proposes countermeasures aimed at providing clear, practical solutions from the source.

1. Abnormal Drill Breakage

Drill fracture during operation is a common occurrence on the shop floor. The primary contributing factors include: excessive feed rate, which causes instantaneous overload; asymmetric drill sharpening, resulting in unbalanced cutting forces on the two cutting edges; and poor chip evacuation, where chips become clogged in the hole and increase torque on the drill—particularly pronounced in deep-hole drilling. In addition to these frequent causes, improper drill selection, mismatch between tool material and workpiece, insufficient machine rigidity, or unstable clamping can also trigger breakage.

Corrective Measures:

Parameter Optimisation: Set feed rate appropriately according to material characteristics, and maintain a steady, uniform feed motion.

Tool Management: Regularly inspect sharpening quality to ensure symmetrical and precise cutting edges.

Process Improvement: For deep-hole drilling, adopt peck-feeding cycles to facilitate smooth chip evacuation.

Equipment Selection: Prefer internal-coolant drills to ensure coolant reaches the cutting point directly.

2. Continuous Chip Winding

When machining ductile materials, continuous ribbon-like chips tend to form, which not only compromises operational safety but may also damage the hole surface. This issue is often related to a mismatch between the drill flute design and the material; additionally, an excessively low feed rate produces thin chips that are difficult to break. Remedial approaches include: moderately increasing the feed rate to enhance chip thickness and promote breaking, or selecting a drill with a dedicated chip-breaker geometry to fragment chips into regular, manageable pieces.

Corrective Measures:

Increase feed rate moderately to increase chip thickness.

Use drills with chip-breaker grooves to facilitate chip fragmentation into regular pieces.

Through appropriate tool and parameter optimisation, safe and efficient chip control can be achieved.

3. Short Tool Life

Premature drill wear compromises machining quality and efficiency. The main causes often stem from improper cutting parameters—for example, excessive spindle speed raises cutting temperatures and accelerates flank wear, while insufficient cooling significantly shortens tool life. To extend service life, rotational speed should be set rationally based on workpiece material, and an adequate supply of cutting fluid with proper flow and pressure must be ensured to cover the cutting zone effectively for both cooling and lubrication.

Corrective Measures:

Optimise the combination of speed and feed rate according to material properties.

Ensure sufficient coolant flow and pressure, precisely directed to the cutting zone.

Select coated drills or materials with higher wear resistance.

Regularly inspect drill wear and establish a documented tool replacement schedule.

4. Oversized Hole Diameter

Holes that are larger than specified after machining affect part fit and assembly quality. Contributing factors include: asymmetrical cutting edges on the drill, which cause the drilling path to deviate; or spindle runout and insufficient clamping rigidity, inducing vibration during entry and exit. Controlling hole diameter accuracy hinges on maintaining precise drill sharpening and regularly checking machine condition to ensure stable clamping and good spindle accuracy.

Corrective Measures:

Strictly ensure the symmetry and precision of drill sharpening; it is advisable to use professional sharpening equipment for regrinding.

Periodically check spindle radial runout and clamping system stability, and perform maintenance when necessary.

For high-precision hole machining, employ pre-drilling or guide bushing processes.

Moderately reduce speed and feed rate to minimise machining vibration.

5. Standardised Operation and Routine Maintenance

Beyond addressing specific issues, cultivating good operating habits is equally important. For example, pre-drilling a pilot hole helps to accurately position the drill; regular inspection of drill wear and timely regrinding preserve cutting performance; and selecting the appropriate cutting fluid and controlling its flow based on material characteristics effectively enhance both machining quality and tool life.

Conclusion

Drilling, as a fundamental machining process, is influenced by numerous factors. Problems such as drill breakage, poor chip control, short tool life, and oversized holes all indicate the need for systematic attention to cutting parameters, tool selection, and operating standards. Through scientific analysis and disciplined practices, the stability and efficiency of drilling operations can be significantly improved.