Why pressing too gently can make stainless steel harder to drill—and why the right answer is not simply to push harder.
When drilling difficult metals, it is tempting to reduce the pressure on the drill to avoid breaking the tool. That instinct is not entirely wrong: excessive feed can overload a drill bit.
But when drilling austenitic stainless steels such as 304 and 316, feeding too lightly can sometimes have the opposite effect. The drill keeps rotating but struggles to penetrate the workpiece. Drilling becomes progressively more difficult, and tool wear can accelerate.
The problem may not be the drill bit’s steel grade or hardness alone. It may involve an often-overlooked material behavior: work hardening.
1. What Is Work Hardening?
Work hardening occurs when a metal becomes stronger and more resistant to further plastic deformation after it has been deformed. Austenitic stainless steels, including common grades such as 304 and 316, are particularly prone to this behavior.
During drilling, the cutting edges do more than remove metal. They also deform material in and around the cutting zone. Some work hardening near the machined surface can occur even under normal cutting conditions.
The goal is not to eliminate every trace of work hardening. It is to maintain effective cutting and avoid repeatedly rubbing or pressing against a surface that has already been deformed.
Two mechanisms should not be confused:
• Work hardening is primarily caused by plastic deformation. It is not the same as hardening a steel through heat treatment.
• Excessive cutting heat can accelerate tool wear and damage the cutting edge, but heat alone is not the direct cause of strain hardening.
These effects can occur together and reinforce poor cutting conditions, but they are not the same physical process.
2. Why Can Too-Low Feed Make Drilling Harder?
Successful drilling requires the cutting edges to remove material continuously and produce chips that can escape through the flutes. When the actual feed per revolution becomes too low, the cutting action may change.
Step 1: Cutting gives way to rubbing and ploughing
If the uncut chip thickness becomes very small, the cutting edge may remove little material. This is especially problematic when the edge is already worn or rounded. Instead of forming chips efficiently, the drill can spend more of its time rubbing, pressing, or ploughing against the workpiece surface.
The drill still spins, but penetration slows.
Step 2: The surface undergoes further deformation
Repeated rubbing and ploughing can plastically deform the near-surface layer of stainless steel. In a material susceptible to work hardening, this can make the next cutting pass more demanding. The drill may then encounter higher cutting resistance as it tries to remove the affected layer.
Step 3: The cutting edge wears faster
Ineffective cutting adds friction and thermal load. If cooling and chip evacuation are also poor, the cutting edge may wear faster. A worn edge then becomes less capable of forming a clean chip, making rubbing and ploughing even more likely.
A possible failure cycle: Insufficient feed → More rubbing and ploughing → Greater near-surface deformation → More difficult cutting → Faster edge wear.
This is a possible failure mechanism, not an inevitable sequence in every low-feed operation. The outcome also depends on drill geometry, tool condition, material state, machine rigidity, lubrication, and other cutting conditions.
3. Feed Pressure and Feed per Revolution Are Not the Same
The distinction matters because “press harder” is not a sufficiently precise machining recommendation.
Feed pressure is the axial force applied to push a drill into the workpiece. It is particularly noticeable in hand-held or manually operated drilling.
Feed per revolution is the actual axial distance the drill advances during one full revolution, commonly expressed in millimeters per revolution (mm/rev).
The two are related, but they are not interchangeable. With a hand drill, the same applied force can produce different rates of penetration depending on sharpness, tool diameter, material properties, and machine setup. On a CNC machine or other controlled-feed system, feed is generally set through machining parameters rather than hand pressure.
The better question is not “How hard should we push?” It is: “At this cutting speed and feed per revolution, is the drill consistently removing material from this workpiece?”
4. More Feed Is Not Always Better
If too little feed can cause trouble, should operators simply use as much feed as possible? No. Excessive feed increases axial force and cutting load. Once the capacity of the drill, machine, or setup is exceeded, the result may be edge chipping, deflection, or breakage.
| Feed condition | Potential consequence |
| Too low | Insufficient chip formation, more rubbing, and possible additional work hardening in susceptible materials. |
| Appropriate | More consistent chip formation, controlled cutting forces, and effective chip evacuation. |
| Too high | Excessive load, with increased risk of chipping, deflection, or drill breakage. |
There is no universal feed setting for every HSS drill bit. The suitable range depends on diameter, tool material and edge geometry, workpiece material, hole depth, machine rigidity, and cooling conditions. Feed recommendations for HSS and carbide drills should not be used interchangeably.
5. How to Reduce Work-Hardening Risk in Stainless Steel Drilling
Maintain a suitable, continuous cutting feed
For stainless steels prone to work hardening, avoid letting the drill rotate against the workpiece for extended periods without meaningful penetration. In manual drilling, aim for a stable, controlled advance rather than prolonged rubbing at one depth. In automated drilling, compare the programmed parameters with the tool manufacturer’s recommended feed per revolution and actual operating conditions.
If the drill is no longer cutting effectively, do not simply force it deeper. Stop safely and investigate the cause.
Use a sharp drill with suitable geometry
A sharp cutting edge is better able to form chips. Increasing force does not necessarily restore the cutting performance of a worn drill—and may increase breakage risk.
For some stainless-steel applications, a properly designed 135° split-point geometry can help reduce walking and improve hole entry. However, point angle alone does not determine performance; edge sharpness, web geometry, rigidity, and manufacturing consistency also matter.
Match cutting speed with lubrication and cooling
Excessive cutting speed can raise the thermal load on the cutting edges. Suitable cutting fluid or lubrication can help manage friction, heat, and chip removal. Speed, feed, and cooling should be evaluated together, rather than adjusting one variable in isolation.
Pay attention to chip evacuation, especially in deeper holes
As hole depth increases, chip evacuation generally becomes more difficult. Trapped chips can increase friction, torque, and heat, potentially contributing to sudden tool failure.
Where appropriate, a properly designed peck-drilling or chip-clearing cycle can improve the process. A controlled withdrawal for chip removal is not the same as allowing the drill to dwell and rub against the bottom of a hole.
6. Why This Matters to Drill Bit Buyers and Distributors
Consider a customer complaint: “This batch of HSS drill bits wears out very quickly when drilling 304 stainless steel.”
It is reasonable to investigate raw material, hardness, heat treatment, and grinding quality. However, a short service life by itself does not prove that the drill bit was manufactured incorrectly. A useful failure analysis also needs information about the application.
Before drawing conclusions, ask:
- • What exact stainless-steel grade and material condition is being drilled?
- • What are the drill diameter, material grade, point geometry, and tool condition?
- • What spindle speed, feed method, and actual feed parameters are being used?
- • Is cutting fluid applied, and is chip evacuation adequate?
- • Is the drill wearing gradually, chipping at the edge, or breaking suddenly?
If different batches show repeatable performance differences under the same controlled cutting conditions, the investigation should focus on material quality, heat treatment, cutting-edge geometry, and production consistency. Conversely, if several otherwise suitable drills struggle under identical operating conditions, the machining process deserves closer attention.
An upgraded steel grade does not automatically correct unsuitable parameters. For example, M35 cobalt HSS may provide advantages in certain high-temperature cutting conditions, but it cannot by itself overcome insufficient feed, poor chip evacuation, or an unstable setup.
Conclusion: Protecting a Drill Does Not Always Mean Reducing Feed
In stainless-steel drilling, a very light actual feed is not necessarily a safer choice. When the drill stops forming chips effectively, continued rubbing and ploughing can aggravate work hardening and accelerate cutting-edge wear.
The solution is not to push harder without limits. It is to establish conditions in which the drill cuts steadily, produces chips, and clears them effectively.
Reliable HSS drill bit performance starts with sound materials, heat treatment, geometry, and consistent manufacturing. It also depends on how the tool is used.
A good drill bit needs both reliable manufacturing quality and the right cutting conditions.
About this series
Why Drill Bits Fail is a technical series written by our production team. Each article focuses on one specific factor in drill bit performance — from raw material to packaging. The goal is simple: help buyers understand what they are actually buying, and which questions to ask.
Post time: Nov-09-2026