The 10 Best Drill Bits For Stainless Steel | Ultimate Guide for DIY Project

When looking to drill through metals like stainless steel, it is imperative to have a drill bit that is robust, heat resistant, and wear-resistant to get the job done.

However, there are significant number of such drills on the market and choosing the right one can be a drill on its own (no pun intended), which is why we have taken our time to research and select some of the best drill bits on the market can be used to drill through stainless steel.

If you looking for a guide on the best drill bit for drilling stainless steel then this blog post will help you to make a decision for your next DYI project. Also this blog post guides you to discover the 10 best drill bits for stainless steel.

Without wasting much time, let’s dive into it.

If you are eager to know about Drilling Through Cast Iron is Risky Or Safe! then read our blog post.

Comparison Table for Better Understanding:

1. Stroton Metric M42 8% Cobalt Drill Bits for Stainless Steel and Hard Metals

If you are looking for a powerful drill bit to puncture holes through stainless steel, then look no further than the Metric M42 8% cobalt drill bits for stainless steel. Thanks to its sturdy and powerful design, this drill bit makes it effortless to get through stainless steel and other hard metals.

To check universality of drill bit or do all drill bits fit all drills read this blog post.

These drill bits are great for all types of projects, from smaller projects to tougher ones, and you can use them for long hours without worrying about them wearing out.

First, the Metric M42 is made with 8% premium cobalt, and adding cobalt to an HSS drill bit makes the M42 drill bit sturdier, wear-resistant, and heat-resistant than an ordinary HSS drill bit.

In fact, by adding 8% cobalt, you increase the red hardness of the drill to temperatures of about 860 to 880 degrees Celsius, and up until those extreme temperatures, the drill bit still maintains its hardness and doesn’t turn red.

The drill bit also has an HRC rating between 68 to 70; therefore, you are guaranteed a fast, non-resistive cutting experience when using the Metric M42 to drill holes through stainless steel or other hard metals, thanks to the 3X speed cutting ability of the drill bit.

Check this blog post for best jigsaw blade for metal cutting.

The drill bit’s tip is engineered with a 3 step design and a 135-degree cutting angle, making the bit edge sufficiently sharp to make it effortless to drill holes through various surfaces, including metals, plastic, wood, and stainless steel.

The Metric M42 8% cobalt drill bits for stainless steel are designed to be efficient, durable, and versatile for both professionals and grilling enthusiasts.

Pros:

• Affordable
• High red hardness
• Tough
• 3 Step design makes drilling 3X more efficient.

Cons:

• Some comments had complained about the drill bit struggling to penetrate thick metals

2. Hurricane Titanium Drill Bits For Stainless Steel Set

If you are on a budget; you need the Hurricane titanium drill bits for stainless steel to get the job done easily. Beyond its aesthetic looks, the titanium drill bit set is well-built and it is designed with cutting-edge technology to help you get the results you want with little to no effort.

The Hurricane titanium twist drill bit set is made from premium high-speed steel materials that make it tough, durable, and penetrative. The HSS material is then treated with titanium to prevent rust and wear during application by preventing heat build-up. This drill bit set can be used for a wide variety of applications from wood, stainless steel, plastic, and fiberglass.

It is designed to give users a fast cutting ability with its 135-degree split point. It automatically gets centered at the penetration point to reduce torque and get through that point effortlessly. In addition to the split point, the drill bit features a twist design and a spiral flute, giving you a faster and easier drilling experience.

This drill bit set is engineered with a round shank to make it compatible with any drill that takes standard drill bits.

In summary, when you purchase the Hurricane Titanium Drill Bits For Stainless Steel set, you are assured of a long-lasting, sturdy, and easy-to-use drill bit that can be used for a variety of applications. It comes in a tough plastic bag to make it easy for you to carry them around without any hassle.

Pros:

• Affordable
• Rust-resistant and wear-resistant
• Compatible with most standard drills

Cons:

• The case doesn’t indicate the sizes of the drill bits and it can be quite confusing for novices to select the desired size.

3. JIUWU Tungsten Carbide Drill Bits For Stainless Steel

Jiuwu tungsten carbide drill bits for stainless steel are another affordable option with all the bells and whistles you need for an effortless drilling experience. This drill bit is engineered to drill precise holes through a wide range of materials ranging from stainless steel, veneers, brass, vinyl siding, copper, and many more.

This drill bit is made of two tough metals: YG cemented carbide and chrome vanadium steel. YG cemented carbide is known to be hard, corrosion-resistant, and wear-resistant. At the same time, chrome vanadium steel is known for its hard tampering. And combining these metals gives you a solid drill bit.

The Jiuwu tungsten carbide drill bits for hardened steel has a tough design, and it is capable of penetrating through most hard materials with ease. It featured a spiral fluke and rounded shanks that make them ideal for cutting faster and cleaner than ordinary drills.

It is built for heavy-duty jobs and can easily penetrate through tough metals and harden steels. It is abrasive resistant, and you can use it for multiple jobs without worrying about sharpening it.

This drill bit set comes in 13 drill bits ranging from 3 mm to 15 mm for all applications for a cleaner and fine drilling experience. However, it doesn’t come in a case, making handling the drill a bit difficult.

Pros:

• Heavy-duty drill bits
• Very durable
• Penetrates a wide variety of surfaces
• Can be used with CNC machines

Cons:

• Quite expensive

4. Neiko Titanium Step Drill Bit For Stainless Steel Set, High-Speed Steel ( 10193A )

The Neiko 10193A Titanium step drill bit for stainless steel is one of the premium drill bits on the market. It has a unique design that combines aesthetics and performance to give you fast and accurate drilling.

This drill bit is made from traditional HSS and then coated with titanium to give its toughness and durability. This titanium coating also prevents the drill from heating up when used for long periods and prevent wearing out when used on hard surfaces such as stainless steel, aluminum, plastic, etc.

This drill is made with a unique 2 flute design that allows for easy penetration when drilling and ensures that you do not hassle when trying to remove the drill bit after penetration, preventing any form of splashing for a clean drilling job.

Check which drill bit left hand or right hand drill bit suitable for your work?

In addition, the 2 flute design ensures that the bit stops at each step to ensure you drill precise and accurate holes without having to drill a hole bigger than you want.

In addition, the drill bit features a tri-flatted shank to ensure that the bit fits perfectly and securely into most drills, therefore, you do not have to worry about the bit removing during work.

To make sure you drill more accurate holes, the drill bit has the laser engraved on the size of each step to help you easily identify the right step to stop at for your holes.

To ensure faster penetration and less use of your energy during work, the tip of the bit is cut at a 135-degree angle, which easily penetrates every type of surface with ease, this 135-degree tip cut angle also prevents the drill bit from walking when drilling at high speeds.

Pros:

• Easy to sharpen
• High heat tolerance
• Durable

Cons:

• Can be challenging to sharpen.

5. Mars-Tools Solid Tungsten Carbide Drill Bits For Stainless Steel

If you are a professional mason or carpenter looking for a robust drill bit that can go for hours of tough work without wearing out, then we present to you the Mars-Tools Solid tungsten carbide drill bits for stainless steel.

This drill bit is built for tough work, and can easily penetrate any surface it encounters. The strength of this drill bit is that it is built from carbide. Carbide is a much tougher and more durable material that provides more rigidity than HSS, which is why we recommend this drill bit to professionals.

This drill bit has a much higher heat resistance and wears resistance than HSS making it an ideal choice for all high-speed. Its heavy-duty applications such as drilling stainless steel, aircraft metals, copper, glass, composite, and many more. Additionally, regardless of how wet or dry the surface of the material you want to drill, this drill bit will easily penetrate the material.

Unlike regular HSS drill bits, this drill bit is uncoated; however, you wouldn’t have to worry about it rusting or wearing off during application.

Diving deep into the design of this bit, this drill bit is engineered with an optimal design ideal for all metalwork. Starting from the tip, this drill bit features an extremely sharp 118-degree four-facet point which ensures you accurately drill the point you want to drill; this 118-degree tip point also ensures that there is no drill walking while you are drilling.

These carbide drill bits for hardened steel have a 118-degree tip also ensure that you have a clean and faster drilling job thanks to the drill bit’s jobber length, which disposes of any chip generated while drilling. This jobber length combined with the spiral flutes gives you a much faster drilling experience than mechanical length drill bits.

Pros:

• Tough drill bit (with a hardness of 913)
• Can be used for extreme drilling
• Long lasting

Cons:

• It is brittle

6. Dewalt Titanium Stainless Steel Drill Bits Set

The Dewalt Titanium stainless steel drill bits set offers extra hardened drill bits to penetrate any metal you throw at it. This is a 21 piece drill bit set, and it comes in a stackable box in a hard plastic case to make it easier for you to transport them. The drill bit set comes in various sizes to fit various applications.

This drill bit set is made from titanium material and then coated with titanium to make it look aesthetic yet purposeful. It features a patented bit-bar design that helps easily remove excess waste and chips.

The tips of these drill bits feature the patented web tapers, which make the drill bit tougher and rigid to prevent easy breakages while working.

Finally, the pilot tip points ensure that you effortlessly penetrate wood, metals, and plastic with little to no effort, and it leaves you with a blur-free hole.

Pros:

• Solid packaging
• Great price point
• Pilot point tips make it easy to penetrate any surface

Cons:

• None

7. BOSCH Best Drill Bits For Stainless Steel Bolts (Cobalt M42 CO14B 14 Pc.)

The Bosch CO14B drill bit is a must-have for DIYers and professionals looking to drill more accurate holes. First of all, the drill bit is made of M42 alloy, which contains 8% cobalt material, making the drill bit more water and heat-resistant.

This addition of 8% cobalt makes the drill bit sturdy and gives it 10X more durability than a standard HSS drill bit, and this makes it an ideal choice for all DIY and professional drilling jobs. This is one of the best drill bits for stainless steel bolts related working.

The tip of the drill bit is engineered with three main features. The first feature is a 1/8″ split point on the tip for easy starting penetrating to eliminate the need of punching the material before penetrating.

In addition, the tip of the drill bit is reinforced to ensure that the bit penetrates robust surfaces without you having to use so much effort. Finally, the drill bit tip is engineered with a thick web helix design to buttress the tip to penetrate hard surfaces, provide more stability, and remove materials faster, especially when dealing with abrasive surfaces.

Finally, the Bosch CO14B drill set features a three-flat shank that ensures that the bit is secured tightly into the drill’s chuck and assures you of no spillage during operations.

Pros:

• Split Point tip
• 10X durability than standard HSS

Cons:

• It is quite expensive

8. IRWIN Best Cobalt Drill Bits For Hardened Steel

Irwin has been in the drilling business for a long time, and they have produced nothing but high-end drills for professionals and DIYers who love to do their drilling. And if you are looking to drill stainless steel and surfaces alike, then the Irwin M35 IRWIN best cobalt drill bits for hardened steel set might be the right choice for you.

The Irwin M35 drill bit set is made of cobalt, and as you may know, cobalt is one of the hardest materials that can get through any surface with ease, and they can withstand pretty much high heat situations, thanks to the high red hardness of cobalt.

It also features a 135-degree split point to prevent the drill bit from sliding during operations. It has heavy-duty construction and features a spiral flute type for quicker penetration and efficient waste removal.

These drill bits come in a sturdy and easy-to-carry case to help you take the drill bits set along with you anywhere you go.

Pros:

• Comes in a solid and simple casing
• The bits are tough and can penetrate thick metals
• Great durability

Cons:

• Expensive

9. Hymnorq Metric M35 Cobalt Steel

The Hymnorq Metric M35 Cobalt steel drill is built for tough drilling jobs. It is composed of a strong and hardened alloy of 8% cobalt, steel, and molybdenum to reinforce the strength of the bit.

By adding cobalt and molybdenum together, you get a drill bit with an HRC rating of up to 67, and this means the drill bit is heat resistant, cuts faster, is hardly breakable, and has a 12 times life span compared to ordinary HSS drill bits. This drill bit can drill continuously under extreme temperatures without becoming red or wearing off.

Besides being made of cobalt steel and molybdenum alloy, the drill bit is coated with bronze oxide, which adds extra strength to the drill bit, helping the drill maintain its sharpness, and prevents friction and corrosion the bit. And as you can already see, the Hymnorq Metric M35 is built for intensive and prolonged metal drilling activities.

The bit’s tip is constructed to have a 135-degree cutting point that centers itself exactly where you want the bit to be, which ensures that you get an accurately drilled hole.

This 135-degree cutting point also prevents the bit from sliding while drilling, and it also ensures that you penetrate the material quickly without the need for any pre-drilling.

The drill bit features a heavy-duty 2-twist flute design, seamlessly penetrating through objects. It efficiently removes any debris generated from the drilling for a smooth and flawless drilling experience.

This drill bit is capable of drilling through objects that have a hardness less than HR38, and this includes objects like stainless steel, copper, galvanized pipe, iron, aluminum alloy, and cast iron.

It has a straight shank which makes it ideal for most drills’ chucks, and it ensures the drill bit is secured tightly into the drill for maximum stability. The shank is also chamfered to fit easily and securely into the drill’s chuck.

Finally, this drill bit set features 13 drill bit pieces ranging from 1.5mm to 6.5mm for various job applications.

Pros:

• Heavy-duty construction made for professionals
• Great casing
• Very durable

Cons:

• Decent performance

10. Drill Hulk 13-Piece M35 Drill Bit Set

The drill hulk drill bits were designed with the professional in mind. It is built to withstand the vigorousness at the job site, and it is sturdily constructed to resist wear and overheating.

To start with this drill bit is made out of high-speed steel and 5% cobalt to improve the heat resistance and red hardness to produce a more strong performance that ensures that you can use it for prolonged hours without it wearing out.

In case it wears out, you can sharpen it as many times as you want without having to worry about damaging the cutting edge. This means you get to have a sharp drill bit ready to perforate any object without hassle.

The drill bit’s tip features a 135-degree split point; this means you get to use less energy to drill holes than the drill bit with split points of 118 degrees.

Also, the 135-degrees split point ensures that the drill bit is centered at the exact point of your choice, and also, when you start to drill, the split point ensures that the drill is in place and there is no slipping or drill walking. This means you can work confidently without having to worry about little errors.

This is a jobber length cobalt drill that ensures that the drill bit effectively removes any debris that is generated during drilling for a cleaner drilling job.

Generally, this drill bit is great for drilling through hard metals and soft metals such as stainless steel, cast iron, aluminum, and many others.

The drill also features a 3-flat shank that provides a secure attachment to the drill chuck to prevent slipping during work, especially with keyless chucks.

Pros:

• Gets rid of chips easily
• Can drill deep holes
• Strong and durable

Cons:

• Casing needs more improvement

Best Drill for Stainless Steel Guide and Example

Looking for the best drill for stainless steel? Before you make your purchase, there are a few things you should think about. First, consider the sort of drill bit you’ll want.

Next, examine the drill bit size. The size you require will be determined by the size of the hole you are attempting to drill. If you’re unsure, it’s always better to go with a larger bit.

Finally, consider the type of drill you want to use. A cordless drill provides the most mobility, while a corded drill provides more power. A corded drill is the way to choose if you’ll be performing a lot of drilling.

To Know about best cordless drill for polishing read this blog post.

Now that you know what to look for, here are our top three stainless steel drill picks:

1. Dewalt DW130V 9.0 Amp Corded Drill – This drill is powerful enough to drill through thick stainless steel. It comes with an HSS drill bit and a carbide-tipped masonry bit, so no matter what you’re drilling into, you’re covered.

2. Bosch 18V Compact 1/2″ Drill – Ideal for drilling through stainless steel and other tough materials.
3. Makita XDT16Z 18V LXT Lithium-Ion Brushless Cordless– This drill is ideal for on-the-go drilling. It features an LED light built in to assist you see what you’re doing and comes with an HSS drill bit.

Whatever sort of drill you want, one of these three alternatives will suffice. So, what are you holding out for? Go ahead and start drilling!

Stainless Drill Bit Buyer’s Guide

When it comes to choosing the right drill bit for drilling stainless steel and other hard metals, there are quite a few things you must look at, and in this section, we will take a look at some of the factors to consider when choosing a drill bit for drilling stainless steel. There are three main things to consider when choosing the right drill, these include:

• The material
• The coating of the drill
• Drill length

Let’s dive deep into these factors to understand them more.

What factors need to consider when you are going to select best drill bit for stainless steel.

The Material

Generally, most drill bits used for drilling through steel are made from three main materials: high-speed steel, HSS and cobalt alloy drill, and carbide.

1. HSS

HSS is also known as the high-speed drill bit is the most affordable available on the market. Even though they can cut through stainless steel, you will require a little bit more effort than the other two materials. In addition, HSS drill bits are more forgiving during drill press.

However, another advantage is that you can easily resharpen it when you realize the drill bit is becoming dull.

2. HSS With Cobalt:

An upgrade to the HSS drill bit is the addition of cobalt to the HSS. Usually, this is done to increase the performance and durability of the ordinary HSS drill bit. These drill bits tend to hold up better than HSS drill bits; however, two major advantages this type of drill has over the generic HSS drill bits are the ability to resist heat and resist wear.

Just like generic HSS drill bits, these types of drill bits can be easily resharpened for longevity. Nevertheless, these drills bits tend to be more expensive than HSS drill bits.

3. Carbide

The best yet most expensive option out of these three are carbide drill bits. Drill bits made of carbide are the most durable and are usually recommended to professionals who are constantly using their drill bits.

If you are just looking for a drill bit for basic DIY projects, you might want to go for either option 1 or 2; however, if you have the budget, you can go in for carbide drill bits. Carbide drill bits are heat and chip-resistant.

These types of drill bits are built solely for hard metals, thanks to the fact that carbide drill bits allow for coolant through holes. Through spindle coolant holes enable you to drill much deeper holes through the toughest materials. This is because they allow for coolant to flow through the drill which flushes out chips quicker for easier drilling.

By allowing coolant to flow through these holes, you get to provide extra lubrication to the cutting point to prevent any heat and wear from friction.

The catch is that regardless of the material you use, either of these drill bit materials will cut through any surface; however, the carbide drill does it quicker and has the most longevity among the two carbide drill bits can outlive HSS and HSS&cobalt drill by 10 to 15 times.

This also means you would have to resharpen the carbide drill 15 times lesser than you sharpen an HSS or an HSS&cobalt drill.

It is important to note too that carbide drills can cost up to 10 times more than the other two options; however, in the long run, the cost per hole of using a carbide drill is far more than the cost per drill for using either of the other two.

Coating

1. Titanium Nitrite

Titanium is the most common form of coating used for most drill bits used to drill stainless steel. Usually, this coating is used because of its heat-resistive property. most drill bits with titanium coating have a bright gold color.

Even though titanium nitrite has a great heat resistance ability, it can only handle so much; therefore, you want to make sure that you do not use them for prolonged hours.

2. Titanium Carbon Nitrite

Drill bits coated in Titanium carbon nitrite are more heat resistive than drill bits coated with titanium nitrite. The drill bits with this type of coating are built for the heavy-duty task, thanks to the fact that they provide a higher surface temperature and are more resistive to wear. Drill bits coated with titanium carbon nitrite usually have a purple-ish coating.

3. Titanium Aluminum Nitride

This is the most solid coating used for most drill bits. If you are going to be drilling solely heavy metals for long hours, then getting a drill bit with titanium aluminum nitride will be very helpful.

This type of coating has the highest temperature resistance than the other two types. Their gray color can identify them, and they are mostly used for drill bits used for stainless steel and other hard or high-temperature metals.

The Length

The length of the drill bit is another factor to consider. When it comes to length, there are various options out there; however, two of the most common lengths used for stainless steel are stub and jobber length.

Drill bits with stub length are more rigid and are used when dealing with tough surfaces. However, they can be of a disadvantage when drilling because they tend not to get chips out effectively, and this can be quite annoying.

Drill bits with jobber length, on the other hand, tend to cost more and they remove chips easily when drilling. However, jobber drills aren’t as rigid as stub drills, and they also tend to be a bit unstable which yields to poor hole precision, so, you want to be mindful of that as well.

Generally, if you are drilling shallow holes, then you may use a stub length drill bit, and if you are looking to drill deeper holes, then a jobber drill bit should do the work.

Size and Number of the Drill Bit

The size of the drill bit is determined by the diameter of the tip. The most common sizes are 3/32″, 1/8″, 5/32″, 3/16″, 7/32″, 1/4″, 9/32″, 5/16″, 11/32″, 3/8″, and 7/16″. The larger the number, the smaller the diameter of the drill bit.

The type of drill bit you use will also be determined by the material you’re drilling into. For example, if you’re drilling into concrete, you’ll need a masonry drill bit. If you’re drilling into metal, you’ll need a titanium or tungsten coated drill bit.

Once you know the size and type of drill bit you need, it’s time to choose the right one for your project. Here are some tips to help you make your selection:

-If you’re drilling into a hard material, like concrete, choose a drill bit with a carbide tip, and diameter with sufficient clearance. This will prevent the drill bit from breaking.

-If you’re drilling into a soft material, like wood, choose a drill bit with a larger diameter. This will help the drill efficient and time saving.

-If you’re drilling into a material that’s difficult to drill into, like metal, choose a carbide drill bit. This type of drill bit is designed to drill through tough materials.

-If you’re drilling a large hole, choose a drill bit with a long shank. This will help the drill bit stay in the hole while you’re drilling.

-If you’re drilling a small hole, choose a drill bit with a short shank.

-If you’re drilling a hole that’s difficult to reach, choose a drill bit with a flexible shank. This will help the drill bit reach the hole.

FAQ

What Are The Best Drill Bits For Metal?

There are various types of drill bits on the market, making it difficult to determine which ones are ideal for drilling into metal. Drill bits with a higher cobalt concentration, are better for drilling through metal. These drill bits are made to withstand high temperatures generated while drilling into metal, and they also tend to stay sharper for a longer period of time.

If you want to acquire the best drill bits for metal, you should seek for ones made of high-speed steel coated with carbide or tungsten. These materials are extremely tough and long-lasting, making them excellent for drilling through metal. You should also seek for drill bits with a 135-degree point angle.

You can read above section of the article for better understanding.

What are the best drill bits for stainless steel? 

 When it comes to drill bits for stainless steel, there are a few things that you need to keep in mind. First, make sure the bit is designed specifically for this type of material. Second, be sure that the bit has a high-quality cutting edge so that it will not wear down quickly. And finally, make sure the bit is comfortable and easy to use so that you don’t experience any arm fatigue or hand cramps. 

 Choose cobalt-coated drill bits for hard metal like spring steel, aluminum alloy etc. And if you want to drill mild still and cast iron, choose titanium coated.  

What are the best drill bits on the market? 

There are many types of drill bits on the market, and it can be difficult to determine which ones are the best for your needs.  

Some popular options include titanium alloy drill bits and cobalt- chrome drill bits. Titanium alloy drills are often lighter and more durable than their copper counterparts, while cobalt-chrome does an excellent job of resisting corrosion in harsh environments like marine applications or industrial settings. 

What is jobber drill bit? 

The term Jobber is referring to its length. Drill bits did not come with different sizes and styles before. The drill bits were more generic than today, known as jobber-length drill bits. 

 Jobber drill bits usually have spiral flutes and are made of HSS steel. Its longer shaft makes the drilling job easy. They are user friendly, less expensive and ideal for general drilling. You cannot use it on hard metal.  

What is the best drill bit for drilling hardened steel? 

 It is important to use the right drill bits when drilling hardened steel. There are a variety of drill bits available on the market, but it is important to select one that is appropriate for the type of metal being drilled. For hardened steel, we recommend cobalt drills. Diamond drills are often considered to produce a finer finish but cobalt helps avoid contamination and wear on the bit. 

Where to buy metric drill bits? 

Buying metric drill bits can be a challenge, but there are a few places where you can find them. Online retailers such as Amazon and Home Depot often sell metric drill bits in packs, while hardware stores may have smaller quantities or specialized items that are not always available online. So, if you’re in need of a specific bit size, it’s worth checking out several different outlets before making your purchase.

What is Metric Drill Bits

1. Metric drill bits are designed for drilling holes in materials measured in metric units.
2. They have a standardized diameter and pitch that corresponds to metric measurements.
3. These bits are typically used in manufacturing and construction where metric measurements are commonly used.
4. They come in various sizes and shapes to accommodate different drilling applications.
5. Some popular shapes include twist, spade, step, and masonry drill bits.
6. They are typically made of high-speed steel or carbide for durability and precision.

 

Who makes the best drill bits? 

You will find a lot of brands including Chinese and USA available in both online and offline selling drill bits. If you want the best among them, we suggest going with native American-made brands such as Dewalt, Makita, Bosch, craftsman, Neiko, Irwin, Drill America etc.      

Final Verdict

There is no doubt that there are tons of options out there when it comes to choosing the best drill bit for stainless steel, and we hope we were able to help you select some of the best drills for drilling holes through stainless steel. Also, we hope our guide helped you understand what to look out for when choosing a drill bit for stainless steel.