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.

In the early 1980s, a team of research metallurgists in Japan led by Dr. Kunio Namiki began experimenting with chemistries to reduce the problems caused by excessive, uncontrolled primary carbides. Other mills had introduced various powder metals to try to overcome these problems. But the metallurgical team determined that the expense of powders and their inability to be welded properly rendered them less than ideal and sought an alternative. They experimented with the following chemistries and percentage ranges:

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.

A second characteristic of the low-carbide grade is its higher degree of hardness—HRC 61-62—than can be obtained with D2—HRC 58-59—when it is tempered at 932 F (500 C). This supports PVD coatings better. If the coating temperature is higher than 932 F, raising the tempering temperature to between 968 F (520 C) and 1,004 F (540 C) still strengthens the steel to between HRC 59 -61 for excellent support of the coating.

As to which steel is best for a given application, the DC53 with 8 percent chromium steel has somewhat better wear uncoated and better temper resistance than the low-carbide grade with 7 percent chromium. The low-carbide grade has higher impact strength and higher fatigue strength. Both will substantially outperform D2 in both coated and uncoated applications. Both offer substantial improvement in tool life compared to D2. Grade selection depends on the failure mode of the current die steel.

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 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.

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.

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.

Forming HSS presents serious challenges. For forming sheet steels above 1,470 MPa, hot stamping is the current practical method. But wear, chipping, fracture, and galling occur during forming of the lower-strength sheet steels from 440 MPa to 1,470 MPa. Coatings such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and thermal diffusion (TD) must be applied to tool steels to prevent galling.

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.

0.6-1.43% carbon (C)/0.28-0.32% silicon (Si)/0.4-0.43% manganese (Mn)/5.09-11.92% chromium (Cr)/ 0.97-1.01% molybdenum (Mo)/0.27-0.31% vanadium (V).

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.

These carbides help with wear resistance only. They reduce impact strength and fatigue strength by acting as a stress riser. Viewed under magnification, a cutting edge of a working D2 die shows small microchips. These occur as a result of the matrix’s fatigue failure around the primary carbide, which causes the carbide to pop out. This left small, jagged areas that can cause further chipping, galling, and cracking. The large irregular carbides also cause cutters and grinding wheels to wear rapidly.

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.

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.

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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.

The Fabricator is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The Fabricator has served the industry since 1970.

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.

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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.

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.

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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.

After 1.5 million hits, both the D2 and steel with 8 percent chromium had pieces missing, while the low-carbide grade was intact. The results were repeated, both with and without PVD coatings.

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.

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.

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.

Interestingly, dimensional growth is nearly the same with the grain direction as across the grain direction. This is attributed to the absence of primary carbides. The DC53 steel with 8 percent chromium will grow dimensionally more with the grain direction than across it. D2 will have even more dimensional variance.

The third-generation low-carbide grade shows no primary carbides, only fine secondary carbides formed in secondary hardening at high-temperature tempering (see Figure 4). The small dark spots are particles formed by manganese and a small amount of sulfur, which results in a dramatic improvement in machinability compared to D2.

Corporate average fuel economy (CAFE) standards mandate that automakers lighten vehicles drastically to meet mileage and emissions targets. That, combined with the need for better crash energy management, has led to a dramatic increase in the use of high-strength steels (HSS) to form automotive structural components.

In 1912, D2 cold-work die steel was introduced to the English tool building market. At that time it represented an advancement in cold-work tooling applications. The chemistry allowed for hardening to HRC 60 by either salt bath or air quench. D2 was sufficiently tough and showed good wear properties for the applications of the period.

Two other ways in which the low-carbide grade has improved over its predecessors are in impact strength and fatigue strength. Its impact strength approaches that of S7. Testing fatigue strength with a rotating bend test at like load shows DC53 with longer life by a factor of 10 times the life of D2, and the low-carbide grade has a lifespan of 10 times that of DC53.

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.

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.

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.

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.

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The researchers concluded that the following chemistry/percentages exhibited the best combination of hardness, fatigue strength, impact strength, and wear resistance plus the favorability for weld repair (see Figure 3):

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.

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.

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.

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 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.

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.

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.

Additionally, dimensional growth in heat treat is a function of the percentage of carbides in the steel. As the carbide runs in the rolled grain direction, more dimensional growth occurs with the grain direction than across it.

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.

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.

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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.

The test was run blanking 1.6-mm-, 440-MPa HSS. Each leg of the square blanking die was made of a different steel. Two were D2, one was the low-carbide grade, and the fourth was the steel with 8 percent chromium. The die was put into service and run 1.5 million hits before inspection (see lead image).

A third characteristic of the low-carbide grade is its dimensional stability. Tempered at 932 F, dimensional change is a modest 0 to -0.05 percent shrinkage. When tempered at higher temperatures, 970 to 1,000 F, dimensional growth is +0.05 to +0.10 percent.Interestingly, dimensional growth is nearly the same with the grain direction as across the grain direction. This is attributed to the absence of primary carbides. The DC53 steel with 8 percent chromium will grow dimensionally more with the grain direction than across it. D2 will have even more dimensional variance.Two other ways in which the low-carbide grade has improved over its predecessors are in impact strength and fatigue strength. Its impact strength approaches that of S7. Testing fatigue strength with a rotating bend test at like load shows DC53 with longer life by a factor of 10 times the life of D2, and the low-carbide grade has a lifespan of 10 times that of DC53.As to which steel is best for a given application, the DC53 with 8 percent chromium steel has somewhat better wear uncoated and better temper resistance than the low-carbide grade with 7 percent chromium. The low-carbide grade has higher impact strength and higher fatigue strength. Both will substantially outperform D2 in both coated and uncoated applications. Both offer substantial improvement in tool life compared to D2. Grade selection depends on the failure mode of the current die steel. Figure 1 Microstructure of D2 shows large carbides.Case ExampleWhen a major automaker was trying to select a die steel to stamp HSS for a significant model change, its final testing for blanking dies came down to the third-generation low-carbide grade and an 8 percent chromium steel with the following chemistry/percentages:C 1/Si 1.5/Mn 0.4/Si 0.05/Cu 0.35; Ni 0.45; Cr 8/Mo 0.9/V 0.1/Al 0.4.D2 was included as a control steel.The test was run blanking 1.6-mm-, 440-MPa HSS. Each leg of the square blanking die was made of a different steel. Two were D2, one was the low-carbide grade, and the fourth was the steel with 8 percent chromium. The die was put into service and run 1.5 million hits before inspection (see lead image).After 1.5 million hits, both the D2 and steel with 8 percent chromium had pieces missing, while the low-carbide grade was intact. The results were repeated, both with and without PVD coatings. The low-carbide grade was selected for all tooling. Slide Show | 5 Images

Trial dies of D2, a third-generation low-carbide steel, and an 8 percent chromium/sulfur steel were run to 1.5 million hits. Both the D2 and steel block dies with 8 percent chromium had pieces of the die missing. The third-generation low-carbide steel was intact even after the results were repeated with and without PVD coatings.

When a major automaker was trying to select a die steel to stamp HSS for a significant model change, its final testing for blanking dies came down to the third-generation low-carbide grade and an 8 percent chromium steel with the following chemistry/percentages:

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.

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.

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.

Advancements in production methods helped improve steel quality and subsequent tool performance. The base chemistry was modified to attempt to extend tool life (see Figure 1).

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.

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.

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.

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.

The improved DC53 tool steels with 8% Cr/2% Mo have proven to hold their hardness well and are a good substrate to support the various coatings. However, the metallurgical team sought to develop a hard steel that would support coatings well, like the DC53, but with even higher impact strength. It formulated a chemistry to further reduce undissolved primary carbides. The chemistry they arrived at was 0.70% C/7% Cr/1.5% Mo/0.15% V.

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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.

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.

The new grade, named DC53, was introduced to the Japanese market in 1987. Soon the new grade had taken many thousands of annual tons of market share from the D2 (SKD 11) and M2 (SKD51) markets. Grade DC53 remains a major cold-work die steel in the industry today.

The inherent flaw in all these “D” chemistries is that the high carbon and carbide-forming elements, especially chrome, led to the formation of large, irregularly shaped, undissolved carbides in the matrix (see Figure 2).

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.

The reduction of primary carbides also facilitated faster machining and grinding. In addition, the alloy performed better at higher draw temperatures—970 to 1,050 degrees F—than D2. This resulted in secondary hardening by precipitating out very fine carbides into the matrix. Additional benefits were less stress for better stability when undergoing electrical discharge machining (EDM); reduced retained austenite; and higher obtainable working hardness (up to HRC 64) than D2.

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.