Drill Bit Chipping
Index
Drill bit chipping occurs when small pieces of the cutting edge fracture or break away. Unlike gradual wear, chipping causes localized damage that can affect hole quality, tool life, and process stability.
Common causes include excessive runout, unstable toolholding or workholding, unsuitable feeds and speeds, inadequate coolant, and poor chip evacuation. The first step is to identify the damage and check the machining conditions, rather than immediately switching to another drill.
This guide focuses on chipping in metal machining, particularly with solid carbide drills. It explains how to narrow down the cause, what to correct, and when a different drill specification may be worth considering.
Drill Bit Chipping: Quick Diagnosis
Where the cutting edge chips, and when it happens during drilling, can help narrow down the likely causes. Use the following table to decide where to begin.
| What You See | What to Check First |
|---|---|
| Chipping is heavier on one side of the drill | Runout and the condition of the chuck, collet, or holder |
| Chipping occurs near the center of the drill point | Entry conditions, chisel-edge geometry, and entry feed |
| Outer corners chip near breakthrough | Exit feed, runout, and workpiece support |
| Chipping occurs with vibration | Tool overhang, holder rigidity, and workholding |
| The cutting edge shows signs of heat damage | Cutting speed and coolant delivery |
| Chips accumulate in the flutes | Chip evacuation, coolant supply, and hole depth |
No single damage pattern proves a particular cause. For example, outer-corner chipping can result from excessive load, runout, or thermal stress. Inspect the drill and review the machining conditions together.
If the same damage appears repeatedly, record its location and the point in the operation when it occurs. These details can help identify whether the problem is related to the setup, cutting conditions, or drill design.
6 Common Causes of Drill Bit Chipping and How to Fix Them
Several machining problems can produce similar cutting-edge damage. The following checks cover the main causes of chipping in solid carbide drilling and practical ways to address them.
1. Excessive Runout
Runout occurs when the drill does not rotate concentrically with the spindle axis. As a result, one cutting edge may remove more material than the other, creating uneven loading and increasing the risk of chipping.
This is particularly worth investigating when one cutting edge shows substantially more damage than the other.
Check the following:
- Cleanliness and condition of the drill shank
- Wear or damage in the collet, chuck, or hydraulic holder
- Correct tool installation and clamping
- Spindle condition and tool overhang
- Measured runout with the drill installed
Compare the measured runout with the tool and holder manufacturers' recommendations. If correcting runout resolves the chipping, changing the drill specification may not be necessary.
2. Unstable Toolholding or Workholding
Even a correctly selected carbide drill can chip when the machining setup allows excessive movement.
Common sources of instability include:
- Excessive tool overhang
- Insufficient holder rigidity
- Poor workpiece clamping
- Thin or unsupported workpiece sections
- Machine vibration or interrupted cutting conditions
Reduce unnecessary overhang, check the holder and fixture, and make sure the workpiece is adequately supported.
If the same drill performs reliably on one machine but chips on another, compare the setups before changing the tool. Differences in rigidity, clamping, or spindle condition may explain the failure.
3. Incorrect Feed Rate
Excessive feed can place more mechanical load on the cutting edge than it can tolerate. However, simply reducing the feed is not always the right solution.
The appropriate feed depends on the drill diameter, geometry, carbide grade, workpiece material, hole depth, and machining conditions.
Pay particular attention to when the damage occurs:
- Entry: An inclined, irregular, or interrupted surface may create uneven loading as the drill enters.
- Steady drilling: Excessive feed may overload the cutting edges or affect chip formation.
- Breakthrough: The load changes as the drill exits the workpiece, potentially damaging the outer corners.
Start with the manufacturer's recommended cutting data. If chipping occurs only during entry or breakthrough, review the feed strategy for that stage instead of changing the entire drilling cycle.
4. Incorrect Cutting Speed
Cutting speed affects temperature, wear, and cutting-edge behavior.
When the speed is too high for the drill and workpiece combination, excessive heat can accelerate wear or damage the cutting edge.
Reducing speed may help if heat is contributing to the problem, but an unnecessarily low speed can introduce other cutting issues, including built-up edge in susceptible materials.
Use the drill manufacturer's recommended cutting-speed range as the starting point. Evaluate changes alongside feed, coolant delivery, and chip formation rather than adjusting speed in isolation.
5. Insufficient Coolant or Thermal Stress
Coolant helps control cutting temperature, lubricate the cutting zone, and carry chips out of the hole. Inadequate delivery can contribute to thermal damage and unstable cutting conditions.
If the drill shows heat-related damage, inspect:
- Whether coolant reaches the cutting edge
- Blocked or restricted coolant holes
- Coolant pressure and flow at the required drilling depth
- Obstructions caused by the fixture or workpiece
- Coolant delivery and concentration against the manufacturer's recommendations
Coolant flowing around the hole does not necessarily mean enough is reaching the cutting zone.
Check actual coolant delivery before assuming that a different coating or carbide grade will solve the problem.
6. Poor Chip Evacuation
When chips become trapped in the flutes or are recut inside the hole, cutting forces and temperatures can increase. Severe chip packing can damage or break the drill.
Inspect the chips produced during machining. Look for:
- Long chips wrapping around the drill
- Chips packed into the flutes
- Chip evacuation becoming worse as the hole gets deeper
- Signs of chips being recut inside the hole
Review coolant delivery, feed rate, flute geometry, and drilling depth against the drill manufacturer's application recommendations.
Chip evacuation becomes especially important in deep holes and difficult-to-machine materials, where limited space and restricted coolant access can make chip removal more challenging.
If chipping continues when drilling stainless steel despite correcting these conditions, the drill's geometry, coolant configuration, and intended application may also need review.
When Should You Replace a Chipped Drill?
A visibly chipped drill should be removed from cutting service for assessment. A damaged cutting edge can affect hole diameter, roundness, surface finish, and cutting forces. Continuing to use it may also lead to further tool damage.
Whether the drill can be reused depends on the extent of the damage and the manufacturer's recommendations.
- Minor damage: Professional inspection can determine whether manufacturer-approved reconditioning is possible.
- Severe edge damage or fracture: Replacement may be required if the drill cannot be restored to its intended specifications.
- Repeated chipping: Investigate the machining process before putting another drill into service.
Replacing a damaged drill and changing to a different drill design are two separate decisions. The first addresses the damaged tool. The second addresses whether the existing specification is suitable for the application.
If a new drill develops similar damage after a comparable number of holes, the recurring failure suggests that the machining conditions or tool selection need further investigation.
When Should You Consider a Different Carbide Drill Design?
A different drill specification becomes worth investigating when chipping continues despite a stable setup and cutting conditions within the manufacturer's recommended range.
Two carbide drills with the same diameter may perform differently in the same operation. Their substrates, cutting-edge geometry, coatings, flute designs, and coolant configurations can influence the types of machining conditions they are suited to.
Use the observed failure to identify which characteristics deserve attention.
| Recurring Problem | What to Compare in Another Drill |
|---|---|
| Repeated cutting-edge chipping | Carbide toughness, edge strength, point geometry, and edge preparation |
| Excessive heat or accelerated wear | Coating, coolant configuration, and recommended cutting conditions |
| Chip packing | Flute geometry, chip-control design, and through-coolant options |
| Chipping in deep holes | Supported length-to-diameter ratio, rigidity, coolant delivery, and chip evacuation |
| Chipping during entry or breakthrough | Point geometry, cutting-edge strength, and suitability for the entry or exit conditions |
| Problems after changing workpiece material | Material-specific carbide grade, geometry, coating, and cutting recommendations |
Use the current failure mode as a selection requirement. A drill chosen to improve chip evacuation may need different characteristics from one intended to withstand interrupted cutting.
Before contacting a tool supplier, record the workpiece grade, hole diameter and depth, current drill series, cutting data, measured runout, coolant conditions, and the location of the damage.
These details make it easier to compare suitable candidates and plan a controlled machining trial. A different drill design should be evaluated under its own recommended cutting conditions rather than automatically using the settings from the existing tool.
Drill Bit Chipping in Stainless Steel: What Changes?
Stainless steel machining can place particular demands on cutting-edge strength, temperature control, and chip evacuation.
Depending on the grade and machining conditions, stainless steel may produce difficult-to-control chips and can be susceptible to work hardening. These characteristics make appropriate cutting data, reliable coolant delivery, and a suitable drill geometry important considerations.
The type of hole also affects the drill requirements.
Deep Holes
As drilling depth increases, evacuating chips and delivering coolant to the cutting zone can become more difficult.
For deep-hole applications, review the drill's supported length-to-diameter ratio, flute design, rigidity, and coolant requirements. Through-coolant drills may be useful when the machining conditions and equipment support their use.
Flat-Bottom Holes
Flat-bottom holes require a drill or cutting tool designed to produce the specified bottom geometry.
Review the point design, entry conditions, and workpiece requirements. A conventional drill may not be suitable for producing the required bottom profile, even if its diameter and material compatibility are correct.
Micro Holes
Small-diameter carbide drills are particularly sensitive to runout, rigidity, and chip evacuation.
For micro-hole applications, confirm the required diameter, drilling depth, machine capability, and toolholding accuracy. The drill's intended depth range and coolant recommendations also need consideration.
Selecting a carbide drill for stainless steel involves more than matching the material and nominal diameter. The hole geometry and operating conditions should also guide the choice.
If repeated chipping has led you to reconsider the current tool, our stainless steel drill guide compares options for deep, flat-bottom, and micro-hole applications.
Frequently Asked Questions About Drill Bit Chipping
Why Does My Drill Chip at Breakthrough?
As the drill exits the workpiece, the cutting forces and material support change. Excessive feed near breakthrough, runout, or insufficient workpiece support can contribute to outer-corner chipping.
Check the drill manufacturer's recommendations for through-hole exits. A feed adjustment near breakthrough may be appropriate for some applications.
Can a Chipped Carbide Drill Be Resharpened?
Some solid carbide drills can be professionally reconditioned, depending on the damage, drill design, and manufacturer's requirements.
However, resharpening may affect the drill's point geometry, edge preparation, coating, or dimensions. Confirm whether an approved reconditioning process is available before returning the tool to production.
Will a Tougher Carbide Grade Prevent Chipping?
Not necessarily. A tougher carbide grade may be useful in applications where cutting-edge fracture is a concern, but chipping caused by excessive runout, vibration, or poor machining conditions will not necessarily disappear with a different grade.
Evaluate carbide toughness alongside cutting-edge geometry, coating, and the demands of the workpiece and hole.
Should I Use Peck Drilling to Prevent Chip Packing?
Peck drilling can help manage chip evacuation in some operations, but it is not automatically the best method for every carbide drill.
Some solid carbide drills are designed for continuous drilling within specified depth and coolant conditions. Introducing unnecessary peck cycles may affect productivity or tool performance.
Follow the drill manufacturer's recommendations for the specific material, hole depth, and coolant arrangement.