Introduction

316 stainless steel is the backbone of medical, food processing, and marine equipment. Its corrosion resistance is unmatched—but the moment you need a hole deeper than 5× diameter, the material reveals its dark side: rapid work hardening, packed chips, and broken drills.

If your shop runs 316 stainless components with deep holes, you've probably experienced this cycle: the drill enters fine, cuts steady for 20–30 seconds, then suddenly squeals, stalls, or snaps. The hole bottom has hardened to the point where even a fresh carbide drill struggles to bite.

At JimmyTool, we've designed custom carbide drills for 316 stainless deep-hole applications for over 15 years. In this article, we'll explain exactly why 316 work-hardens so aggressively in deep holes—and more importantly, what you can change in your drill geometry, coolant delivery, and pecking strategy to stop the cycle.

Why 316 Stainless Work-Hardens So Aggressively in Deep Holes

Before fixing the problem, we need to understand the physics. 316 stainless steel isn't inherently hard—in its annealed state, it measures around 150–200 HV (roughly HRB 80–90). The problem is what happens during drilling.

1. The Rubbing-Not-Cutting Threshold

Austenitic stainless steels like 316 have exceptionally high ductility and a high work-hardening rate. When the cutting edge enters the material, if the feed per revolution is too low relative to the cutting edge radius, the tool "rubs" instead of shearing. This rubbing generates intense frictional heat at the hole bottom—and that heat triggers the phase transformation that hardens the surface layer. Once hardened, the subsurface microhardness can increase by over 100%, reaching above 500 HV in the affected zone. The next drill revolution now faces material significantly harder than when it started.

2. The Confinement Effect in Deep Holes

In shallow holes, heat can dissipate through the workpiece and chips can escape freely. In deep holes (beyond 5× diameter), the drill body acts as a plug, trapping heat and chips at the hole bottom. The trapped heat continuously "soaks" the uncut material ahead of the drill tip, essentially pre-hardening it before the cutting edge even reaches it. As the hole gets deeper, the material progressively work-hardens, becoming even more difficult to cut.

3. Chip Packing and Recutting

316 stainless produces long, stringy chips due to its high ductility. In a deep hole, if these chips aren't evacuated instantly, they pack around the drill flutes and get ground between the drill body and the hole wall. This recutting action generates additional heat and friction, accelerating work hardening of the hole wall—and dramatically increasing torque on the drill until it snaps. Work hardening can be particularly pervasive when drilling deep holes because there is a tendency to "peck" drill, which introduces repeated entry and exit cycles that expose the material to intermittent heating and cooling.

The JimmyTool Shop Observation: When we analyze failed drills from 316 deep-hole jobs, the dominant failure pattern is not gradual flank wear—it's catastrophic breakage caused by chip packing and torque spikes. The root cause is almost always insufficient chip evacuation combined with inadequate cooling at the hole bottom.
Upload Your Drawing for a Custom Deep-Hole Drill Quote →

4 Proven Fixes to Stop Work Hardening During Deep Hole Drilling in 316

Here are four actionable adjustments that directly address the work-hardening and chip-evacuation challenges unique to 316 stainless deep-hole drilling.

1. Choose Drill Geometry Engineered for Stainless

Standard 118° general-purpose drills force high thrust loads onto the chisel edge, which work-hardens 316 stainless almost immediately. Center punching with conventional conical-shaped punches can similarly create enough localized work hardening at the surface to make drill entry difficult, potentially causing the drill tip to deflect, wander, or blunt before it even begins to cut effectively.

For drilling 316 stainless, specify these geometric features:

• 135° Split Point Geometry: A 135° split point is self-centering—requiring no center punch—and generates significantly less thrust force than a standard 118° point. This reduced thrust translates directly into less frictional heating and lower risk of work hardening. The split point's reduced thrust force is particularly valuable in stainless steel because high drilling pressure increases heat generation at the cutting zone, accelerating work hardening.

• Increased Back Taper: Increasing the back taper (the gradual reduction in drill diameter from tip to shank) reduces contact between the drill body and the hole wall. This minimizes friction, heat generation, and the tendency for chips to weld to the tool margins.

• Wider Parabolic Flutes: Standard drill flutes clog quickly with the long, stringy chips 316 produces. Wider parabolic flutes dramatically improve chip evacuation and prevent the chip packing that causes catastrophic torque spikes.

Related Product: Explore our Custom Carbide Through-Coolant Drills for Stainless Steel Deep Hole Applications featuring 135° split-point geometry, parabolic flutes, and optimized back taper designed specifically for 304, 316, and duplex stainless steels.

2. Use Through-Coolant Delivery at Adequate Pressure

This is the single most impactful change you can make for deep holes in 316. External flood coolant cannot reach the hole bottom once depth exceeds 3× diameter—the drill body blocks the fluid path. The result is dry cutting at the most critical location.

A Through Coolant Drill solves this by using internal helical channels to deliver pressurized coolant directly to the cutting edges. This technology eliminates the pecking cycle and forces chips to travel in one direction: out. Internal cooling provides the necessary lubrication to keep chips sliding, which is critical in 316 stainless where heat causes chips to "weld" to the tool flutes—a failure mode known as built-up edge (BUE).

The recommended coolant pressure for deep hole drilling in 316 stainless is at least 70 bar for holes deeper than 5× diameter. Even for smaller diameters, adequate pressure remains essential—with smallest hole diameters (starting at 0.3 mm), a coolant pressure of 15 bar is still necessary to achieve effective cooling.

The payoff is significant: switching to internal cooling has been shown to extend tool life by over 200% and slash cycle times by nearly half in stainless steel deep-hole applications.

Further Reading: For a deeper dive into the mechanical advantages, read our complete guide to Through Coolant Drills: 5 Reasons It's Mandatory for Deep Hole Efficiency.

3. Rethink Your Pecking Strategy

The traditional approach to deep holes—aggressive pecking (drill a short distance, fully retract, repeat)—is counterproductive in 316 stainless. Every retraction and re-entry cycle interrupts the cutting process and exposes the hole bottom to intermittent heating and cooling.

The better approach for 316 stainless with through-coolant capability is continuous drilling: drill to full depth in a single stroke while coolant pressure handles chip evacuation. This eliminates the thermal cycling that accelerates work hardening and drastically reduces cycle time.

If your setup requires pecking, follow these guidelines:

• First Peck: Equal to drill diameter.

• Subsequent Pecks: Reduced to 25% or less of the drill diameter to limit heat buildup at the hole bottom.

• Never Dwell: Never allow the drill to dwell at the bottom of the hole without feeding—this rubs and instantly work-hardens the surface.

• Avoid Pecking When Possible: If you are doing production quantities of 316 stainless, avoid peck drilling if possible due to the work hardening risk.

4. Run the Right Parameters: Slow Speed, Steady Feed

The cardinal rule of drilling 316 stainless: keep the feed up and the speed down. If the cutting speed is too high and the feed is too slow, the drill will rub rather than cut, which creates heat and actively work-hardens the material. Once that hardened layer forms, subsequent drilling becomes exponentially more difficult.

For carbide drills in 316 stainless, the following ranges are supported by multiple experimental studies:

Caution: Always ensure rigid workholding and minimum drill overhang. Any vibration or deflection will cause uneven engagement at the cutting edge, accelerating work hardening in local zones.

For medical and food equipment applications where 316 components require certified hole quality and repeatable tool life, it's also worth considering deep cryogenic treatment of the cutting tools. Research has shown that deep cryogenic treatment combined with optimized drilling parameters can significantly improve surface roughness and roundness error in AISI 316 drilling operations.

When to Consider a Custom Carbide Drill for 316 Deep Holes

Standard catalog drills are designed for general-purpose use. For demanding 316 stainless applications—especially holes deeper than 8× diameter, tight-tolerance medical components, or production runs where tool change downtime is costly—a custom drill often delivers payback within the first batch.

Consider a custom carbide drill when:

• Hole depth exceeds 8× diameter in 316, requiring specialized flute geometry for chip evacuation.

• Tight diametral tolerances (±0.01mm or better) demand a drill ground specifically for your material and coolant setup.

• Thin-walled components require low-thrust geometries to prevent deformation.

• Combined operations (drilling + chamfering, drilling + counterboring) could eliminate a tool change.

Our application team has engineered custom carbide drills for 316 stainless that doubled tool life and halved cycle time compared to catalog tools—by optimizing the split-point angle, flute width, back taper, and coolant-hole positioning for one specific part number.

Conclusion

316 stainless deep hole drilling doesn't have to be a drill-breaking nightmare. Work hardening is driven by heat, friction, and poor chip evacuation—all of which are controllable when you match the right drill geometry with adequate coolant delivery and correct cutting parameters.

The proven formula: 135° split-point carbide drill + through-coolant at 70+ bar + continuous drilling (no peck) with steady feed at moderate speed will transform your 316 deep-hole process from a source of scrap and downtime into a stable, predictable operation.

Battling a specific 316 stainless deep hole right now?
Share your part drawing and current setup details with our team. We'll recommend a custom carbide drill solution within 12 hours—engineered specifically for your material, hole depth, and machine capability.

Upload Your Drawing for a Custom Deep-Hole Drill Quote →

Frequently Asked Questions About Deep Hole Drilling in 316 Stainless Steel

Q1: Why does 316 stainless steel work-harden so quickly during deep hole drilling?
316 stainless is an austenitic stainless steel with high ductility and a high strain-hardening rate. When the cutting edge rubs rather than shears—caused by insufficient feed rate, improper drill geometry, or dwell—frictional heat triggers a transformation in the material surface. In deep holes, heat becomes trapped at the hole bottom (the drill body acts as a plug), continuously pre-hardening the uncut material ahead of the drill tip. Subsurface microhardness can increase by over 100%, reaching above 500 HV.
 

Q2: What is the best drill point angle for 316 stainless steel?
A 135° split-point geometry is strongly recommended for 316 stainless. Unlike standard 118° points that require high thrust force and can cause the drill to "walk" at entry, a 135° split point is self-centering and generates significantly less thrust force—approximately 30–40% less—which directly reduces frictional heating and work-hardening risk. This geometry is particularly critical in deep holes, where any additional heat at entry compounds throughout the drilling depth.
 

Q3: Is through-coolant really necessary for drilling deep holes in 316 stainless?
Yes, and it becomes essential once hole depth exceeds 3× drill diameter. At that depth, external flood coolant cannot reach the hole bottom—the drill body blocks the fluid path. Through-coolant drills with internal channels deliver pressurized coolant (minimum 70 bar for holes deeper than 5× diameter) directly to the cutting edges. This provides continuous cooling, lubrication, and hydraulic chip evacuation. Shops that switch report tool life improvements exceeding 200% in stainless steel deep-hole applications.
 

Q4: Should I use peck drilling for deep holes in 316 stainless?
If through-coolant is available, avoid peck drilling entirely. Continuous single-stroke drilling eliminates the thermal cycling from repeated entries and retractions that accelerates work hardening. If your setup cannot use through-coolant and pecking is unavoidable, follow these rules: first peck equals drill diameter, all subsequent pecks reduced to 25% or less of drill diameter, and never allow the drill to dwell at the hole bottom.
 

Q5: What cutting speed and feed rate should I use for carbide drills in 316 stainless?
For carbide drills with TiAlN or AlCrN coatings, use cutting speeds of 14–25 m/min and feed rates of 0.05–0.15 mm/rev. Multiple studies support these ranges: research using the Taguchi method found that minimum surface roughness and roundness error were achieved at 14 m/min cutting speed with 0.08 mm/rev feed rate. M35 cobalt drills tested at 800 rpm with 0.05 mm/rev feed rate also yielded excellent cylindricity in 316 deep-hole drilling. Keep the feed up and the speed down—too high a speed with too low a feed causes rubbing that instantly work-hardens the material.
  

Q6: What coating performs best for carbide drills in 316 stainless?
Both TiAlN (Titanium Aluminum Nitride) and AlCrN (Aluminum Chromium Nitride) are effective for 316 stainless. AlCrN offers excellent resistance to high temperatures and thermal shocks, with a maximum working temperature of up to 1100°C, making it an ideal choice for machining with high mechanical and thermal loads. Research has shown that the lowest wear when machining 316L was observed with an 8-layer TiAlN coating at a specific TiN/TiAlN ratio. For deep-hole applications where thermal management is critical, AlCrN is recommended for its superior oxidation resistance.
 

Q7: Is a pilot hole recommended before deep hole drilling in 316 stainless?
Yes, a pilot hole slightly larger than the chisel edge of the main drill (typically 25–30% of the main drill's full diameter) is recommended. This eliminates the high-thrust dead zone at the center and improves hole position accuracy. However, ensure the pilot hole is drilled at the same or slightly lower speed to avoid work-hardening the pilot hole walls, which would then damage the main drill on entry.
  

Q8: When should I consider a custom carbide drill instead of a standard catalog item for 316 stainless?
Consider custom tooling when hole depth exceeds 8× diameter, tight diametral tolerances (±0.01mm) are required, thin-walled components demand low-thrust geometries, or when combined operations could eliminate tool changes. A custom carbide drill from JimmyTool—with geometry, coating, and coolant-hole positioning engineered for your specific part—often doubles tool life and halves cycle time compared to off-the-shelf alternatives.