The tools used in deep-hole drilling are usually durable since they are made of super-strong materials and have unique geometries. As such, these tools can withstand wear and prevent consistent tool changes. Hence, the extended tool life of deep-hole drilling machines helps to save costs while ensuring peak productivity.

Because of its hardness, stainless steel is an unforgiving construction medium. Usually, there is only one chance to achieve the perfect drill hole. Another crucial consideration when purchasing drill bits for stainless steel is the drill bit number or size.

In our stainless steel drilling tests, these Milwaukee bits surprised us with noticeably faster, more precise penetration into the steel. The elevated pilot point, which is visibly shorter and narrower than others tested, seemed to offer the best balance of accurate placement and rapid material removal. We also noted that the center point did not get in the way of sharpening like some of the other pilot-point bits. Plus, Milwaukee’s hard plastic carry case was our favorite of the entire test group. It held the bits more securely, offered easy-to-read size indexing, and was easy to open and close securely. If the bit size assortment were more comprehensive, this set could have been our Best Overall pick.

However, full-face crown drill bits exhibit improved lifespan even though it is subjected to the hardness and rigidity of the material’s surface. Therefore, it is advisable to use the right drill bits to drill precise and accurate holes easily.

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We really liked the effectiveness of the pilot-point design. Instead of using a punch to mark the starting point and reduce bit travel, the pilot point allowed us to start drilling directly into the flat surface. However, due to its multitiered structure, we noted that the pilot point complicates the process of sharpening the bit. We worked through it slowly and with extra caution, we achieved satisfactory results.

Folks who want to be ready for tough steel drilling projects that might come up should consider these cobalt bits from Bosch. The kit includes 14 bits ranging in size from 0.0625 inch to 0.5 inch. They are made of M42 cobalt alloy steel, which is one of the best bit materials for drilling hard metals like stainless steel, cast iron, or titanium. The bits feature easy-to-sharpen split points and 3-flat shanks for easy, secure chucking into the drill. They also feature thicker threading than other twist bits, which helps them remove material more efficiently in less time.

High-speed metal drilling creates excessive friction and heat. The extra stress placed on standard drill bits tends to wear them out quickly. Individuals who intend to drill stainless steel frequently should be sure to buy bits designed with longevity in mind.

Not all drill bits achieve results in the same way. To identify the best drill bits for stainless steel, learning about characteristics like material, coating, frequency of use, and drill bit number are critical. Read on to learn the factors to consider as you search for the best drill bits for your projects that involve stainless steel.

Later on, the technology advanced and extended to other applications, including making automotive parts like cam-shafts, crank-shafts, fuel rail, and fuel injector bodies, creating lo holes in injection molding, aerospace parts like landing gear, different parts in the oil and gas sector, general engineering components like hydraulic cylinders, etc.

Deep hole drilling is a process of machining a hole ten times deeper than the hole diameter. A deep hole is characterized by at least a depth-to-diameter ratio of up to 10:1. It is suitable for creating holes of desired depth in different CNC machining materials ranging from aluminum to the strongest super-alloys.

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Product manufacturers and designers rely on different deep-hole drilling processes to achieve superior-quality final products while controlling costs. This section discusses the standard techniques used in deep hole drilling:

This set of M42 cobalt drill bits from Drill America includes 29 pieces from 0.0625 inch to 0.5 inch in 0.015625-inch increments. The bits are finished with gold oxide, which acts as a built-in lubricant to minimize heat, making this one of the best choices for a long working life when drilling tough metals. Each bit is made of high-grade M42 cobalt alloy steel and features a split point and straight shaft.

We also keyed in on bits with 135-degree points as the recommended angle for efficient drilling into hard metal at the required lower speed and higher pressure. Other variables, such as split or pilot point, flat or 3-flat shank, or various coatings held lower priority. Lastly, we factored in top brand names, which often equate to greater consistency and availability.

Carbide is one such material found in drill bits for stainless steel. Titanium and tungsten carbide are nearly as hard as diamond, making them ideal for penetrating steel. These carbide-infused drill bits are one strong option when drilling straight into stainless steel.

Using the appropriate drill bit to drill straight holes is essential to avoid drill deviation or inaccuracies. Drilling deep holes with incompatible drill bits can result in expensive mishaps. As such, manufacturing experts often prioritize the drill bit’s compatibility and durability.

Deep hole drilling techniques offer the tight tolerances and high accuracy required in machining aerospace components such as landing gear and turbine blades. Deep drilling processes produce holes exactly to tolerances to ensure optimal performance and low weight of these components.

With the above considerations in mind, we selected the following drill bits as our top picks for drilling stainless steel. Read on to find out the details on each set, how they performed in our drilling tests, and why we included them among the best drill bits for stainless steel.

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This guide discusses everything you need to know about deep hole drilling, its benefits, applications, and standard techniques. You’ll also learn helpful tips for effective deep-hole drilling. Let’s dive in!

The oil and gas industry benefits from deep-hole drilling because it helps make boreholes for oil and gas extraction. The process offers extreme depth-to-diameter ratios in long workpieces without compromising wall thickness or accuracy in roundness. Deep hole drilling is perfect for making holes with a depth-to-diameter ratio of up to 20:1.

Moreover, you must feed the metal-working fluid through an annular space between the inner and drill tubes. Then, the fluid comes out from the side of the drilling head, flowing over the drill head to cool and lubricate it. The fluid pushes the chip through the internal cavity of the inner drill rod for efficient removal. Introducing some of the fluid into the thinner tube ring nozzle would be best.

AT-Machining is the right machining partner for your CNC and deep-hole drilling needs. We leverage our range of hole-drilling machines with our machinists and product engineer expertise to achieve preferred tolerances and outstanding accuracy in your final products and prototype machining. We have years of experience offering reliable deep-hole drilling services across all fields.

Many manufacturers complement construction materials like drill bits with metal coatings. These coatings promote penetration and protection of the drill bit. Black oxide coatings reduce friction and heat—a significant consideration when drilling metals. Black oxide also protects against corrosion and water, keeping the drill bits functional for a longer period.

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Titanium nitride (TiN) protects high-speed drill bits. Distinctive for their golden color, TiN-coated drill bits are ideal for high-speed drills. The coating provides the ancillary benefit of being ultradurable, making them an excellent value for consumers who intend high-frequency use.

The Drill America bits offered a similar drilling experience as our Best Overall pick because of their similar design features, but this set boasts improved durability thanks to a higher cobalt content. Both sets offered the same drill-bit size assortment, round shank, and 135-degree split-point construction. The Drill America bits remained noticeably sharper after an equal number of test holes, but they required three or four more passes on the grinder to sharpen.

We certainly appreciated that the Irwin cobalt drill bit set had the best selection of bit sizes, in tight increments of 0.015625 inch from one size to the next. It would make a great choice for anyone who requires a high degree of precision in terms of hole sizes. However, in testing we saw that the straight shanks required a little extra care when chucking to ensure a secure fit without slipping. The straight shanks also made the bit a smidge more likely to get stuck if we applied too much pressure.

Drill bit numbers are related to wire gauge size. The larger the bit number, the smaller the diameter of the resulting hole. For example, a number 80 drill bit creates a hole with a diameter of 0.0135 inches. As the diameter grows larger, the bit number grows smaller. A number 1 drill bit, in comparison, has a diameter of 0.2280 inches.

In addition to ultrahard materials and protective coatings, drill bit users who seek longevity should ensure the bit can be sharpened. While drill bits infused with carbide or cobalt keep their edge longer than a standard bit, investing in a set for life often means resharpening the dull drill bits over time.

The DeWalt 14-piece Industrial Cobalt Alloy drill bit set is built for working on hard stainless steel, with features to prevent bit breakage, shank slippage, and travel on the work surface. The set includes 14 bits made of durable M35 cobalt alloy steel. It includes the most popular bit sizes from 0.0625 inch to 0.375 inch. Pilot points make it easy to start drilling precisely where the hole needs to be, while the 3-flat shank design prevents slipping in the drill chuck.

Meanwhile, the defense industry is another primary field where deep-hole drilling is widely embraced. Manufacturers in this field use this drilling strategy to make accurate holes in the gun barrel with the preferred surface finish.

Stainless steel is an extremely hard material. Low-carbon steel bits, like those used to drill into wood, do not perform when applied to stainless steel. Therefore, a drill bit for use with stainless steel must be harder than the steel itself. One way that manufacturers achieve this hardness is by infusing materials that facilitate penetration and protect against overheating.

Since deep hole drilling operations are automated, they allow precise and accurate depth-to-diameter ratios in drilled holes. Hence, deep drilling is ideal for attaining holes with dimensions that are exact to requirements in industries such as aerospace and defense.

We liked the compact round carry case that these bits come in. The screw-on top held securely and seemed to be watertight after we accidentally dropped it in a puddle. However, the bit-size indexing was all but impossible to read. Although the large quantity of bits makes the set heavy, this would be a good choice for carrying to project sites where precision drilling is required.

Ejector drilling or a double-tube system is often used on machining centers and conventional machine tools. It provides drilling depths of about 100 x D. Despite being a BTA drilling system variant; it has no sealing to prevent the metal-working fluid at the workpiece from exiting. Therefore, this drilling technique is suitable for oblique boring or discontinuous parts since covering up the metal-working fluid circuit is impossible.

Deep hole drilling can be quite complex, irrespective of the sophistication of the machinery. Also, there are higher chances of errors when drilling a deep hole. However, here are some helpful considerations for effective hole drilling:

Deep hole drilling processes offer a better surface finish than conventional methods done with twist drills. Deep drilling involves the use of specialized tools and setups for high-pressure coolant flow and effective chip evacuation, ensuring the superior surface quality of the hole. Consequently, this excellent surface finish mitigates friction and wear, ensuring the durability and proper performance of moving parts.

Modern industries like aerospace benefit a great deal from deep-hole drilling. Here are the typical roles this operation plays in respective applications:

Though drill bits for stainless steel pull heavier duty, they are also made of more durable materials. Regularly maintained and properly stored, these kinds of drill bits may last a lifetime.

The technological advancement of drilling equipment allows you to attain a certain depth-to-diameter ratio since a computer controls the process. Similarly, there are different deep-hole drilling techniques with varying modes of operation. Hence, choosing the one that fits your project demands best is essential.

Those with lingering inquiries about drill bits for stainless steel may find the info they need in the answers to these frequently asked questions. It should help folks use and maintain the best drill bits for particular projects.

The typical drill bits for making deep holes in wood are Auger bits. These drill bits have a helical or spiral shape and comprise a sharp point on their tip, allowing drilling efficiency. This tip efficiently pulls the bit through the drilled wood to achieve the preferred depth.

The 3-flat shank prevented bit slippage in the chuck and eliminated most snags in the drill work when excessive pressure was applied. The heavy-duty plastic carry case was easy to use and light enough to tote in a tool bag. Overall, it’s a nice all-purpose choice for everyday use with stainless steel and most other metals.

Deep hole drilling is a complex metalworking process that involves making long, straight holes in components. As such, workpiece deflection can occur when the workpiece is not properly held in position, resulting in inaccuracies. Therefore, it would be best to ensure workpiece stability when making holes.

Machinists often encounter common mistakes like misalignment or drill bit incompatibility, resulting in scrapped parts, poor surface finish, and excessive machine tool wear. Consequently, you may have to incur additional machining costs and experience delayed production.

Manufacturers often use specialized equipment designed explicitly for deep-hole drilling procedures. These innovative equipment are set up to optimize the hole drilling operation for straightness and efficiency.

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We found the 135-degree split tip to be very easy to sharpen. Also, the steel carry case proved durable and well organized with easy-to-read size indexing, although it weighed more than the heavy-duty plastic cases used by competitors. It’s probably best to keep this set in the shop and use a smaller set for traveling work.

Coolants are crucial in deep hole drilling because they ensure proper cooling and lubrication of the hole drilling operation. These coolants help to maintain moderate temperatures, ensuring longer tool life.

In some project settings, a single step drill bit can replace an entire set of twist bits. Step bits offer the advantage of fast, clean precision drilling into thin stainless steel or sheet metal without the need to change between different bit sizes. Each one of the three cobalt step drill bits in Milwaukee’s set is engineered to drill up to 1,000 holes into 14-gauge steel. They feature a rapid strike tip for fast starts without a center punch, elongated dual flutes to minimize heat, and finer step increments for smoother operation. Hole sizes are laser engraved inside the flutes for easy reference.

Deep hole drilling is a popular metal-working process in many fields, especially in producing firearms or heavy ordinances. This operation is perfect for most high-precision drilling projects because it provides highly accurate, repeatable holes with superior surface finishes. Therefore, it is crucial to understand everything about deep hole drilling to achieve the best results.

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Infusing drill bits with cobalt is another way that manufacturers achieve ultrahard drill bits. High-speed steel, also known as HSS, is the most common drill bit for metal drilling. Cobalt drill bits are an extension of HSS bits. They are made with a special steel alloy that includes 5 percent to 8 percent cobalt.

The 3-flat shanks of these bits eliminate slippage in the drill chuck. The combination of secure chucking, easy starting, and smooth operation make these bits an excellent choice for use in cordless drills at low speed for hard stainless steel or higher speed for mild steel. The kit includes Milwaukee’s #1, #4, and #9 step bits. The #1 drills from 0.125-inch to 0.5-inch holes in steps of 0.03125 inch. The #4 bit makes holes 0.1875 inch to 0.875 inch in 0.0625-inch steps. The #9 bit drills 0.875-inch to 1.125-inch holes in 0.0625-inch steps.

Generally, a normal drilling process has a length-to-diameter ratio usually smaller than 5. Hence, deep-hole drilling is characterized by a length-to-diameter ratio greater than 5.

Solution: Using drill bits with the correct geometry, material, and coating on the workpiece material would be best to avert this challenge. You can use drill bits with solid carbide or diamond coatings for better wear resistance. However, optimize feed rates, speed, and coolant selection to mitigate heat and ensure proper cutting frequency.

Besides, the BTA tooling or single tube system comprises a hollow drill tube fastened to a threaded indexable cutter head, depending on the diameter and depth of the hole that requires drilling. The diameter range of the BTA tools ranges from 0.80 – 8.00 inches (20 – 200mm) and can attain depths of about 16.00 inches (400mm).

We appreciated the affordability of this kit’s overall packaging and design, which allowed the tool quality to remain high while minimizing branding and engineering costs. The bits functioned comparably to similarly designed bits from bigger brand names, with good drilling capability and an easy-to-sharpen point. We also liked that the kit includes duplicates of several smaller sizes, as they are the ones that dull easiest and are more susceptible to breaking under excessive pressure. The case does feel a bit flimsy and the size selection is somewhat limited, so this won’t be a great fit for those who require high precision. But for occasional drilling, it’s a really good deal.

These tips got into the material quickly and smoothly transitioned out to the full diameter of the bit. The edges held up remarkably well compared to M35 bits, but the tip design called for greater care when it finally came time to sharpen. We had to work slowly using extra caution to maintain the multitier tip profile.Though the thin plastic case is nothing to brag about, the size indexing was easy to read.

If converting fractions of an inch to the metric system seems like no fun, this 19-piece drill bit set can help. Not only are these Stroton bits metrically sized in increments of 0.5 millimeters, from 1 millimeter to 10 millimeters, they also feature a unique three-stepped pilot-point design that penetrates stainless steel without traveling across the flat surface. The bits are constructed of tough M42 cobalt alloy steel for improved durability.

Engineers and product designers in the automotive field rely on deep-hole drilling to achieve preferred tolerances in machining automotive parts and components. For instance, the fuel injectors in vehicle engines require small and highly accurate holes to inject fuel into the combustion chamber efficiently. Also, the crankshafts and cylinder blocks require precise deep holes to function effectively.

Although deep hole drilling has extensive material compatibility, each material poses challenges. Certain materials, such as plastics, may experience deformation, while rigid materials like titanium may cause consistent machine tool wear during deep hole drilling.

Solution: Use special fixturing mechanisms to steady the workpiece, mitigate deflection, and ensure drilling accuracy. Also, it is advisable to plan the drill entry point carefully to reduce impact and mitigate chances of deflection.

The Boring and Trepanning Association introduced the BTA drilling in the 1940s. This process involves inserting a special hollow tooling in the hole pushing pressurized coolant into the hole on the outside of the drilling tool during the operation. Then, it removes the chips through the hole within the drill.

Following the guidelines on this revolutions per minute chart, we used each bit to drill four holes into 0.125-inch thick stainless steel, observing the ease of penetration, any bit travel across the steel surface, and the formation of metal chips/dust. We also noted how securely the bit was retained by the drill chuck and, when drilling by hand, how smoothly it transitioned from point penetration to the full diameter of the bit. Finally we used a bench grinder to sharpen the bits and drilled another hole with each one. Each of the sets we picked tested successfully, with the primary differences or improvements being edge retention, tip and shank design, and set configuration.

Available in several grades, each with at least 10.5 percent chromium, stainless steel is popular because of its low maintenance, high sheen, and resistance to stains and rust. DIYers and trade professionals often need to drill stainless steel to complete a variety of electrical, plumbing, and automotive projects. Whether you’re expanding the size of a junction box punch-out or boring out a broken bolt, having the right drill bit matters. Drill bits built to work on softer material, like wood, won’t do the trick against stainless steel. Luckily, manufacturers design special drill bits capable of puncturing even the hardest grade of stainless steel.

With loads of available bits for hard metal applications, finding the right drill bits for stainless steel can be challenging. We spent more than 40 hours researching the best materials and designs used to make these bits, selecting our top picks, and then testing our picks in the workshop. Read on to find out what makes a durable and effective drill bit for stainless steel, our selection criteria, and how our selections performed in testing.

Milwaukee Cobalt Red Helix drill bits make it easy to drill into hard stainless steel. This set includes 15 bits made of M35 cobalt alloy steel. They feature pilot points for fast, precise surface penetration without a center punch or pilot hole and 3-flat shanks to eliminate the hassle of bits spinning in the chuck. Bit sizes range from 0.0625 inch to 0.375 inch.

The added cobalt content makes these drill bits harder and more resistant to heat buildup than a typical HSS bit, giving them much greater durability. Also, unlike carbide tips or titanium coatings, cobalt drill bits can be resharpened when the tip becomes worn. These bits offer precision to users who drill stainless steel and other hard materials.

The gun drill comprises a straight flute cutting edge and a single internal coolant hole. As such, you can supply pressurized coolant through the inner holes while you remove chips through the single-flute gun drills within the shank. Hence, material removal occurs at the same time as the drilling.

In testing, the Bosch M42 drill bits made drilling a pleasure thanks to their unique combination of design features. The M42 alloy itself allowed the bits to hold their sharp edge longer than others we tested, which meant more holes with less work stoppage to resharpen. The split-point design was easy to sharpen when needed and only required two or three additional passes on the grinder compared to M35 bits from other sets. The 3-flat shank was fast and easy to chuck securely, and we never had to worry about the bit slipping or becoming stuck in the work surface.

These high-pressure coolants are also responsible for efficient chip evacuation from the cutting zone, preventing surface damage and chip removal strokes that may take time. Coolants allow the drilling process’s productivity and improve the hole quality.

While the Stroton M42 cobalt bits feature round shanks, which can allow slippage in the chuck, we did not experience any slippage during tests, possibly thanks to the unusual low-profile stepped split-point design. Unlike the more pronounced pilot points on other bits we tested, the low-profile Stroton tips featured a three-step tip that seemed to penetrate faster and smoother than other designs, with or without a center punch starting point.

Titanium carbonitride (TiCN) is likely the most durable metal coating available. TiCN bits are blue-gray. Their coating makes them incredibly resistant to wear and capable of enduring high-speed and high-frequency use.

Also, deep-hole drilling is pivotal in machining hydraulic cylinders for engineering vehicles and other industrial applications. These hydraulic cylinders are crucial for bulldozers, forklifts, excavators, etc. Deep hole drilling is ideal for making holes with the desired precision to ensure seamless motion.

This deep-hole drilling method uses a machine with a thin cutting tool to achieve highly accurate and straighter holes in a workpiece. The introduction of gun drills transformed the drilling game because they offer higher accuracy than conventional-style drills.

For affordable drilling options, we chose these bits made of a proven material with a simple and functional design. The Comoware cobalt twist bit set includes 15 bits made of M35 cobalt alloy steel that dependably penetrate stainless steel. The bits feature an easy-to-sharpen split point and a straight shaft. They range in size from 0.0625 inch to 0.375 inch, including two each of the popular 0.0625-inch, 0.09375-inch, and 0.125-inch sizes, for a total of 12 different bit sizes. The kit comes in a lightweight plastic carry case with easy-to-read printed bit-size indexing.

A rubber-reinforced carrying case protects the drill bits from accidental drops and makes organization and transportation a snap. These drill bits work well on stainless steel and last a long time.

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Over the course of 2 days, we spent about 12 hours shop testing the drill bits we selected. After unpacking and noting the physical characteristics of each bit set and the cases they came in, we started drilling. From each set, we tested four different bits, first in a drill press for precision and accuracy, then in a cordless drill to gauge comfort and smooth operation.

Here are some of the challenges you may encounter during deep hole drilling operations and helpful ways to overcome them:

Deep hole drilling is a widely used technique in many industry applications. However, it originated from the need to drill straight gun barrels with high accuracy in which the required depth-to-diameter ratio can reach 20:1.

This 29-piece professional-grade drill bit set from Irwin Tools covers an abundance of applications. The bit circumference spans 0.0625 inches to 0.5 inches by increments of 0.0156 inches. The bits themselves are heat- and abrasion-resistant, thanks to their industrial-grade high-speed steel cobalt-alloy construction. To aid penetration, these bits feature 135-degree split-tip points. Besides making these bits suitable for ultrahard materials like steel, the quality construction materials ensure longevity.

Deep-hole drilling differs from regular drilling since cooling lubricant must be passed to the cutting edges in high volume and under high pressure, depending on the intended drilling technique and diameters.

Deep hole drilling is a versatile process that benefits various applications with stringent requirements and unique challenges in machining rigid materials with tight tolerances. This operation offers the preferred depth-to-diameter ratio for your hole-drilling projects. However, it would help to understand everything about the process to effectively exploit its benefits in achieving high-quality products.

However, you might be able to perform the deep hole operations with a standard CNC gun drilling machine, depending on the hole’s depth-to-diameter ratio. However, you can use special tools to achieve higher precision. A specialized deep-hole drilling system can achieve larger diameters of about 400:1.

Solution: Partner with a service provider with vast knowledge of the techniques and tools used in deep-hole drilling. Similarly, it is advisable to implement process documentation and quality control measures to mitigate human errors and detect mistakes early.

In our tests, we appreciated the Milwaukee step bits’ ability to drill precise holes without a center punch using a handheld drill. They tapped into the stainless steel quickly and worked smoothly. We also noted how easily they worked to enlarge existing holes—a task that’s nearly impossible to do well with regular twist drill bits. Sharpening the bits was surprisingly easy but required a completely different technique than twist bits. We used a diamond sharpening stone to flatten the smaller flute edge, and it only took about 5 minutes.

We spent several days researching drill bits for stainless steel and shopping around for the best options available online. Although solid carbide drill bits may be the professional machinist’s choice for drilling stainless steel, they are incredibly expensive. Other options like titanium-coated HSS are inexpensive but lack durability. We narrowed our search to cobalt drill bits because they can drill hard metals repeatedly without dulling right away, and they can be resharpened many times to extend their working life.