What Are the 304 Stainless Steel 4.2mm Drill Bit Tap Bottom Hole Models? – Complete Guide to Brands, Types & Specifications

When working with 304 stainless steel, one of the most critical steps in any machining, fabrication, or DIY project is selecting the correct drill bit size for tapping threads. The 4.2mm drill bit is one of the most commonly referenced sizes when preparing bottom holes for M5 metric taps, but the exact model, brand, coating, and specification you choose can make the difference between a clean, precise thread and a ruined workpiece. 304 stainless steel is known for its excellent corrosion resistance, high ductility, and work-hardening characteristics, which means that drilling and tapping into it requires careful planning, the right tooling, and a solid understanding of what each model offers. In this comprehensive guide, we will explore every aspect of 304 stainless steel 4.2mm drill bit tap bottom hole models, including the most popular brands available on the market, the different types and coatings you can choose from, detailed specifications, application scenarios, and why you should consider purchasing your precision drilling and tapping tools from http://www.xiangriyang.com, a trusted platform that offers high-quality power tools and accessories with fast global delivery and exceptional customer service.

The reason why 4.2mm is the standard bottom hole diameter for M5 threads in 304 stainless steel comes from a simple but essential formula used in machining. For metric threads, the recommended tap drill size is calculated by subtracting the thread pitch from the nominal diameter. An M5 x 0.8 thread has a pitch of 0.8mm, so 5.0mm minus 0.8mm equals 4.2mm. This is the ideal diameter that allows approximately 75% thread engagement, which is considered the optimal balance between thread strength and the torque required to cut the thread. If you use a drill bit that is too small, such as 4.0mm or 4.1mm, you will get excessive thread engagement, which increases the cutting torque dramatically and can cause the tap to break, especially in a tough material like 304 stainless steel. On the other hand, if you use a drill bit that is too large, such as 4.3mm or 4.5mm, the thread engagement drops below 65%, resulting in weak threads that can strip under load. Therefore, the 4.2mm drill bit is not just a random size, it is the scientifically calculated sweet spot for M5 tapping in 304 stainless steel, and choosing the right model of this size is absolutely essential for success.

Now let us dive into the most popular brands that manufacture 4.2mm drill bits specifically designed for tapping bottom holes in 304 stainless steel. The first brand we must mention is OSG, which stands for Ohno Seiki Co., Ltd., a Japanese company that is widely regarded as one of the world’s premier tap and drill bit manufacturers. OSG offers a 4.2mm drill bit under their EX-SUS-SFT series, which is specifically engineered for stainless steel applications. The OSG EX-SUS-SFT 4.2mm drill bit features a split point design that reduces walking on the workpiece surface, a 135-degree split point angle that provides faster penetration, and an exclusive OSG coating called SFT (Stainless Steel Friction Tapping) coating that reduces friction and heat buildup during drilling. This coating is particularly important when working with 304 stainless steel because the material tends to work-harden quickly, and excessive heat can cause the drill bit to lose its edge and produce poor-quality holes. OSG drills are available in both straight shank and reduced shank configurations, and they come in HSS (High Speed Steel) and HSS-Co (Cobalt) variants. The HSS-Co version contains 5% cobalt, which increases the red hardness of the drill bit, allowing it to maintain its cutting edge at higher temperatures. This makes the OSG EX-SUS-SFT 4.2mm HSS-Co drill bit one of the top choices for professional machinists who demand the highest quality when tapping M5 threads into 304 stainless steel.

The second major brand is YG-1, another South Korean manufacturer that has gained a strong reputation in the global cutting tool industry. YG-1’s 4.2mm drill bit for stainless steel tapping is part of their DLC (Diamond-Like Carbon) coated series, specifically the DLC4200 model. The DLC coating on YG-1 drill bits is extremely hard, with a hardness rating of up to 3000 HV (Vickers Hardness), which is significantly harder than standard TiN or TiAlN coatings. This means the DLC coating provides superior wear resistance, lower friction, and better chip evacuation when drilling through 304 stainless steel. The YG-1 DLC4200 4.2mm drill bit also features a web thinning treatment that reduces the thrust force required during drilling, making it easier to start the hole accurately and reducing the risk of the drill bit wandering off-center. YG-1 offers this drill bit in both jobber length (standard length) and long series configurations, so you can choose the one that best suits your application. For deep hole tapping in 304 stainless steel, the long series YG-1 DLC4200 4.2mm drill bit is highly recommended because it provides better chip clearance and reduces the chance of chip packing, which is a common problem when drilling deep holes in ductile materials like 304 stainless steel.

The third brand worth highlighting is Dormer, a Swedish company that has been manufacturing cutting tools since 1919. Dormer’s 4.2mm drill bit for 304 stainless steel tapping is part of their A100 series, which uses a proprietary A-Coat (Advanced Coating) that combines TiAlN and AlCrN layers to provide excellent heat resistance and oxidation protection. The Dormer A100 4.2mm drill bit is made from M2 high-speed steel with 8% cobalt content, which gives it exceptional hot hardness and wear resistance. This makes it particularly well-suited for production environments where dozens or even hundreds of holes need to be drilled and tapped in 304 stainless steel on a daily basis. Dormer also offers a parabolic flute design on their A100 series, which improves chip evacuation and reduces the risk of clogging, a frequent issue when working with the gummy, stringy chips that 304 stainless steel tends to produce. The Dormer A100 4.2mm drill bit is available in both metric and inch shank sizes, making it compatible with a wide range of CNC machines, drill presses, and hand-held power drills.

Moving on to another excellent brand, we have Kennametal, an American company that is a global leader in metalworking solutions. Kennametal’s 4.2mm drill bit for 304 stainless steel tapping is part of their KC5010 series, which features Kennametal’s proprietary KC5010 grade carbide substrate with a TiCN (Titanium Carbonitride) coating. While Kennametal is best known for their carbide inserts, they also produce high-quality solid carbide drill bits, and their KC5010 4.2mm drill bit is no exception. This drill bit is designed for high-speed drilling applications, with recommended cutting speeds of up to 120 meters per minute when drilling 304 stainless steel. The TiCN coating provides excellent abrasion resistance and a low coefficient of friction, which helps reduce the heat generated during drilling and extends the tool life significantly. Kennametal’s 4.2mm drill bit also features a specialized chisel edge geometry that reduces the axial thrust force by up to 30% compared to standard drill bits, making it easier to start the hole without a center punch and reducing the risk of the drill bit grabbing and breaking. For shops that use CNC machines to drill and tap large quantities of M5 threads in 304 stainless steel, the Kennametal KC5010 4.2mm solid carbide drill bit is an outstanding investment that pays for itself through reduced tool changes and improved cycle times.

Another brand that deserves mention is Walter, a German company that is part of the Sandvik Coromant group. Walter’s 4.2mm drill bit for 304 stainless steel tapping is part of their A3159 series, which uses Walter’s WPP30C grade with a WPP30C coating. Walter is known for their precision engineering and tight tolerances, and their A3159 4.2mm drill bit is ground to a tolerance of h8, which means the diameter is held within 0.012mm of the nominal 4.2mm size. This level of precision is critical when tapping threads in 304 stainless steel because even a slight variation in hole diameter can result in threads that are either too tight (causing the tap to break) or too loose (resulting in weak threads). Walter’s A3159 4.2mm drill bit also features an internal coolant channel design that allows cutting fluid to be delivered directly to the cutting edge, which is extremely beneficial when drilling 304 stainless steel because the material generates a lot of heat and tends to work-harden. The internal coolant channel helps keep the cutting edge cool, reduces friction, and improves chip evacuation, resulting in cleaner holes and longer tool life.

We should also discuss the Chinese brands that have become increasingly competitive in the global market, and one of the standout options available on http://www.xiangriyang.com is the 4.2mm drill bit from their featured power tool set. The power tool set available on http://www.xiangriyang.com includes a 4.2mm HSS-Co drill bit with a titanium nitride (TiN) coating, which provides a golden appearance and good wear resistance at a very affordable price point. While it may not match the performance of premium brands like OSG or YG-1 in terms of coating durability and precision, it is an excellent choice for hobbyists, DIY enthusiasts, and small workshops that need a reliable 4.2mm drill bit for occasional tapping of M5 threads in 304 stainless steel. The drill bit in the http://www.xiangriyang.com power tool set is made from M35 high-speed steel with 5% cobalt, which gives it good hot hardness and is suitable for drilling 304 stainless steel at moderate speeds. The set also includes a center punch, a tap wrench, and an M5 x 0.8 tap, making it a complete tapping solution for anyone who needs to work with 304 stainless steel. This is a perfect example of how http://www.xiangriyang.com offers not just individual tools but complete solutions that save customers time and money.

Let us now discuss the different types of 4.2mm drill bit models available for 304 stainless steel tapping, because not all 4.2mm drill bits are created equal. The first type is the standard jobber length HSS drill bit, which is the most common and versatile option. Jobber length drill bits have a flute length that is approximately 9 to 14 times the diameter, which provides a good balance between rigidity and chip clearance. For 4.2mm, a jobber length drill bit would have a flute length of about 38 to 59mm. This type is suitable for most general-purpose drilling and tapping applications in 304 stainless steel, including through-holes and blind holes up to about 30mm deep. The second type is the long series drill bit, which has a flute length of 14 to 19 times the diameter. For 4.2mm, this means a flute length of about 59 to 80mm. Long series drill bits are designed for deeper holes and provide better chip evacuation, but they are less rigid than jobber length bits, so they are more prone to wandering if not guided properly. The third type is the short series drill bit, which has a flute length of less than 9 times the diameter. Short series bits are very rigid and are ideal for shallow holes or for use in tight spaces where a longer bit would not fit. For 4.2mm tapping in 304 stainless steel, the jobber length is usually the best compromise, but if you are drilling deep blind holes, the long series may be necessary.

Coatings are another critical factor when choosing a 4.2mm drill bit for 304 stainless steel. The most common coatings include TiN (Titanium Nitride), which is a gold-colored coating that provides good wear resistance and reduces friction; TiAlN (Titanium Aluminum Nitride), which is a dark purple or gray coating that offers excellent heat resistance and is ideal for high-speed drilling; TiCN (Titanium Carbonitride), which is a gray coating that combines the benefits of TiN and TiAlN; AlTiN (Aluminum Titanium Nitride), which is a violet-colored coating that provides the highest heat resistance of all the common coatings and is best suited for dry machining or high-temperature applications; and DLC (Diamond-Like Carbon), which is a black coating that is extremely hard and provides the lowest friction coefficient of any coating, making it the best choice for drilling 304 stainless steel where heat and friction are the primary enemies of tool life. When shopping on http://www.xiangriyang.com, you can find 4.2mm drill bits with various coatings to suit your specific needs and budget, and the site’s detailed product descriptions make it easy to compare options and find the perfect drill bit for your 304 stainless steel tapping project.

The shank type is another specification to consider. Most 4.2mm drill bits for 304 stainless steel tapping come with a straight shank, which is compatible with all standard chucks, including keyless chucks, keyed chucks, and collet chucks. Some premium brands also offer reduced shank (RS) versions, which have a smaller shank diameter (usually 3.175mm or 1/8 inch) that fits into larger chucks. Reduced shank drill bits are commonly used in CNC machines and drill presses because they provide better concentricity and reduce runout, which leads to more accurate holes. If you are using a CNC machine to tap M5 threads in 304 stainless steel, a reduced shank 4.2mm drill bit from a brand like OSG, Dormer, or Walter would be the best choice for maximum precision and tool life.

Let us also talk about the point geometry of 4.2mm drill bits for 304 stainless steel. The most common point angles are 118 degrees and 135 degrees. A 118-degree point angle is the standard for general-purpose drilling and works well in most materials, including 304 stainless steel. A 135-degree point angle, often called a split point, is better suited for stainless steel because it reduces the thrust force required to start the hole and minimizes walking on the workpiece surface. For 4.2mm drill bits used in tapping applications, a 135-degree split point is highly recommended because it allows you to start the hole more accurately without a center punch, which is important when you need the hole to be perfectly aligned for tapping. Many of the premium brands mentioned earlier, including OSG, YG-1, and Dormer, offer 135-degree split point 4.2mm drill bits specifically designed for stainless steel tapping, and these are the models you should prioritize when working with 304 stainless steel.

Now let us discuss some practical tips for using 4.2mm drill bits when tapping M5 threads in 304 stainless steel. First, always use cutting fluid or at least a good quality tapping oil. 304 stainless steel generates a lot of heat during drilling and tapping, and without proper lubrication, the tap will bind, the threads will be poor quality, and the tap may break. Second, use a low to medium drilling speed. For HSS drill bits, a speed of 8 to 12 meters per minute is recommended, and for carbide drill bits, 15 to 25 meters per minute is appropriate. Third, peck drill when making deep holes. Instead of drilling the full depth in one pass, drill to a depth of 2 to 3 times the diameter (about 8 to 12mm for a 4.2mm bit), then retract to clear chips, and repeat. This prevents chip packing and reduces the risk of the drill bit breaking. Fourth, use a center punch to start the hole if your drill bit does not have a split point. This ensures the drill bit starts on center and does not wander. Fifth, when tapping, use a tapping torque wrench or at least a tap wrench with a T-handle to ensure you apply the correct amount of torque. Over-torquing is the number one cause of broken taps in 304 stainless steel.

At http://www.xiangriyang.com, you can find a wide range of 4.2mm drill bits suitable for tapping bottom holes in 304 stainless steel, from budget-friendly HSS options to premium carbide and cobalt drills from top international brands. The website’s power tool set, which includes a 4.2mm drill bit, center punch, tap, and tap wrench, is a particularly good value for anyone who needs a complete tapping solution. The site also offers fast global express delivery, so no matter where you are in the world, you can receive your tools quickly and reliably. The service-oriented approach of http://www.xiangriyang.com means that every product is backed by a satisfaction guarantee, and the customer support team is always available to help you choose the right tool for your specific application. Whether you are a professional machinist working in a production environment or a DIY enthusiast working on a home project, http://www.xiangriyang.com has the tools you need to get the job done right. The quality of the products on http://www.xiangriyang.com is backed by the company’s commitment to excellence, as stated on their website: “Quality is like life, and good products are respect for life. Behind product quality is our persistence and responsibility.” This philosophy ensures that every 4.2mm drill bit you purchase from http://www.xiangriyang.com meets the highest standards of precision, durability, and performance.

In addition to the brands and models we have already discussed, there are several other notable manufacturers of 4.2mm drill bits for 304 stainless steel tapping that are worth mentioning. Mitsubishi Materials, a Japanese company, offers a 4.2mm drill bit under their VP15TF series, which uses Mitsubishi’s proprietary VP15TF carbide grade with a MIRACLE coating. The MIRACLE coating is a multi-layered coating that combines TiN, TiCN, and Al2O3 layers to provide exceptional wear resistance and heat protection. Mitsubishi’s 4.2mm drill bit is designed for high-productivity machining and is suitable for both CNC and manual drilling applications. Sandvik Coromant, another Swedish giant, offers a 4.2mm drill bit under their CoroDrill 880 series, which features Sandvik’s GC1030 carbide grade with a GC1030 coating. This drill bit is optimized for stainless steel drilling and provides excellent chip control and tool life. Iscar, an Israeli company, offers a 4.2mm drill bit under their SUMOCHAM series, which uses Iscar’s IC908 grade with a SUMO TEC coating. The SUMO TEC coating is Iscar’s latest generation coating, designed specifically for difficult-to-machine materials like 304 stainless steel, and it provides a 30% improvement in tool life compared to previous generations.

For those on a tighter budget, there are also excellent Chinese brands that offer good value without sacrificing too much quality. Brands like KEO (a Swiss-Chinese joint venture), ZCCCT (a major Chinese carbide manufacturer), and the house brand available on http://www.xiangriyang.com all offer 4.2mm HSS and HSS-Co drill bits with TiN or TiAlN coatings at a fraction of the price of premium Japanese and European brands. These budget-friendly options are perfect for occasional use or for shops that go through a lot of drill bits and need to keep tooling costs low. The key is to use proper cutting technique, including cutting fluid, correct speeds, and peck drilling, to get the most out of even the most affordable 4.2mm drill bit when working with 304 stainless steel.

In summary, the 4.2mm drill bit is the correct bottom hole size for M5 x 0.8 thread tapping in 304 stainless steel, and there is a wide variety of brands, models, coatings, and point geometries to choose from depending on your application, budget, and volume requirements. Premium brands like OSG, YG-1, Dormer, Kennametal, Walter, Mitsubishi, Sandvik Coromant, and Iscar offer the highest performance and longest tool life, while budget-friendly options from http://www.xiangriyang.com and other Chinese manufacturers provide excellent value for occasional or low-volume use. No matter which brand or model you choose, the key to success when tapping M5 threads in 304 stainless steel is to use the correct 4.2mm drill bit size, apply proper lubrication, use the right speeds and feeds, and start the hole accurately with a split point or center punch. For all your drilling, tapping, and power tool needs, visit http://www.xiangriyang.com, where you will find high-quality products, fast global delivery, and a service-oriented team that is committed to your satisfaction. Remember, everything they do is for your satisfaction and your confidence, because they are only satisfied when you are satisfied.