Adding to the fact that this material is difficult to mill, the hard spots also can lead to inconsistent machining results. According to Cory Cetkovic, product manager, Big Kaiser, Hoffman Estates, Ill., it is important to take note of these hard spots in the material and determine the most appropriate tool to handle a range of hardnesses within the material.

Emuge’s TiNox-Cut product range consists of submicron grain carbide end mills for difficult-to-cut materials, particularly aerospace materials. Photo courtesy of Emuge.

Fortunately, masonry drill bits that can tackle these types of jobs do exist, such as this 260mm-long drill bit from DeWalt. Featuring a two-cutter carbide head with individual cutting tips at 140 degrees for more efficient drilling, this lengthy drill bit has a hardened steel body to reduce the likelihood of breakage. Reviewers were impressed by the quality on offer here, especially for the price.

The majority of masonry drill bits are made from tungsten carbide, a tungsten-carbon compound that resists abrasion well, and can withstand the high temperatures generated from drilling brick or concrete. Diamond-tipped bits are also available, but are usually way in excess of what a DIYer will need, both in terms of cost and specifications – although they’re the preferred choice for core drill bits.

Short answer: no. The most common kind of drill bits have a round shaft, and are suitable for the most popular drills; the kind of multipurpose drill that you’re already likely to have. They’re perfectly suitable for light to moderate work, and should be up to the job of drilling through most masonry.

Arriving in a touch plastic box that opens up as a stand, selecting and returning the drill bits into the casing is easy. The bits themselves are heat-treated to minimise the risk of breakage. Amazon reviewers awarded excellent scores for durability, sturdiness and longevity – which is exactly what you want from your masonry drill bits.

Beyond substrate, geometry, and edge prep, adding a coating can be a big asset. Cetkovic explained that a coating can have a huge influence on chip evacuation, which is extremely important in this heat-resistant material.

"Enhancing the efficiency of machining cobalt chrome can be accomplished by keeping a close eye on the tool life, for all the tools in the process, and frequently changing tools to ensure that you are cutting the material and not rubbing the material with dull tools," said Foschaar. "Most times cutting parameters are drastically reduced in this material to avoid poor tool life, but there is a fine line or small window to machine within for cobalt chrome."

Erbauer’s diamond-tipped core drill set is mighty in more ways than one. For that sizable price tag, you get three core drills in key sizes, all stored in a high-quality flight case. As well as the 38, 52 and 117mm core drills, it features a 200mm extension bar for deeper drilling, 115mm SDS adapter, 90mm hex adapter, an 8 x 205mm pilot drill, and a 75mm drift key to help remove the pilot bit from the pilot hole.

"Tools designed for nickel-based alloys or tools for hardened materials are also suitable for this material," said Foschaar. "Nose end mills or square end mills with corner radii are usually ideal for this material. It’s also important that the tools are sharp. Dead sharp tools should be avoided due to the rapid decline of the cutting edge, which will cause rubbing, and a work-hardening situation will occur."

A selection of commonly used sizes from a well-known brand and with an appealingly low price tag, there’s very little to quibble about when it comes to these DeWalt masonry drill bits. They’re designed to power through concrete, masonry, brick and both natural and artificial stone, featuring a rounded shaft that will fit the widest range of drills.

Proper cooling at the cutting edge, reducing tool projections as much as possible, and using a very strong, rigid fixture setup on the machine will help deal with the challenges of milling cobalt chrome. With the high price of the material, ensuring process reliability through proper tool selection and cutting parameters is essential.

There are several challenges that operators should be aware of when milling cobalt chrome. The material tends to be extremely abrasive, which causes the cutting tools to dull prematurely and reduces the life of the tool.

There are five bits in the set, which come in two lengths – both of which are longer than is common at these diameters – and are stored in a plastic case. The tips are tungsten carbide, while the drill bit is made from hardened steel and features U-shaped flutes that are designed to efficiently sweep out debris from the drill hole.

Foschaar added that solid-carbide tools are preferred for machining cobalt chrome materials. Carbide cutting tools generally have thermal shock-resistant properties while at the same time have a high degree of bending strength and fracture toughness, making them suited for the characteristics of this material.

If you’re drilling through two courses of brick or a single course of blockwork, you’ll need a drill that will be long enough to avoid going through the hassle of having to drill through the reverse side. You’ll need to factor in the width of the bricks or blocks, the mortar, internal plaster and any external wall coverings such as render, plus the size of any cavities, too.

"Cobalt chrome is considered a DTC [difficult-to-cut] material due to its high hardness, corrosion resistance, high melting points, and incredible strength at high temperatures," said Chris Foschaar, application and sales engineer, Horn USA Inc., Franklin, Tenn. Foschaar added that there are many variations of the material, with an average hardness of 40-50 HRC. Depending on the type of cobalt chrome, the material also can carry hard spots throughout upwards of 58-60 HRC.

He explained that for operators or shops that haven’t come across it or are now just starting to get into it, they may find it very disappointing because of the SFM rating and tool life expectancy. However, once a shop has worked out the correct machining parameters and knows how to approach the material, it can successfully machine cobalt chrome and get the best tool performance.

Below you’ll find a selection of the best drill bits available, covering SDS Plus, hex and round twist-drill options. Our picks take into consideration price, online review ratings, and the selection of bits offered in a set to ensure you’re able to choose the best masonry drill bit for you.

Horn’s Torus end mill is carbide grade TSCC for machining of cobalt chrome alloys. It comes with a 2- to 5-fluted design with a 30-degree helix angle. Photo courtesy of Horn.

Because of this, the heat concentrates at the cutting edge of the tool," said Doiron. "This is where the geometry of the tool plays a big role in its ability to absorb that heat and chip away the material. Also, when working with cobalt chrome, establishing proper cutting parameters is vital to prevent tool failure."

"We also tend to see some variability when it comes to coolant delivery," said Cetkovic. "We’ve also seen a large number of cases where customers are dry machining these materials."

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This is generally because of the low thermal conductivity of the material. Cetkovic explained that when cutting, the tool will absorb a lot of the heat. Adding coolant as the tool exits the cut can cause it too cool down quickly, which can cause the tool to fracture because of thermal shock. Machining cobalt chrome dry can help operators avoid situations like this.

Proving that a good set of SDS Plus drill bits needn’t cost the earth is this set from Wigan-based UK Drills. The SDS Plus set includes seven bits in five diameters and two lengths, presented in a robust metal case – which should shrug off damage better than the brittle plastic alternatives.

"These materials also can be polished at an extremely high level, which eliminates surface areas where bacteria can form in medical devices," said Dan Doiron, milling product manager, Emuge Corp., West Boylston, Mass.

"This in turn causes the next challenge, which is work hardening of the material," said Foschaar. "These challenges can be minimized by selecting the proper cutting tools for the application."

Often thicker, studier and longer than other types of drill bits, masonry drill bits have a slightly wider tip to help clear the path for the rest of the bit. In general, they’re best paired with a hammer drill, although depending on the surface you’re drilling into, and the size of the hole you wish to make, you might be able to get away with using a powerful standard drill. Note that, in our opinion, you’d be wise to spend extra on a drill bit from a known brand, since cheaper units can be prone to failure when the going gets tough.

Luminoso has a bachelor of arts from Carleton University, a bachelor of education from Ottawa University, and a graduate certificate in book, magazine, and digital publishing from Centennial College.

Cetkovic added that operators need to be aware of the high work-hardening rate of this material. He suggests that a slow feed rate, although better for cutting tool life, could also result in this work hardening, so it’s important to discuss with cutting tool manufacturers the range of cutting speeds (SFM) that the tool can handle in the material. To extend tool life, he also recommends a low depth of cut.

Hex drill sets suitable for masonry aren’t as common as those with a round shaft or SDS fitment, which probably goes some way to explain the popularity of this EZARC set. That, and the super-positive reviews it’s received from thousands of users.

"I think everyone who cuts this material, or at least has been in the industry, understands how difficult it is," said Doiron.

Big Kaiser’s end mills are designed to increase productivity and meet some of the most challenging application requirements. These micro cutting tools are produced using solid carbide with a reinforced shank to maximize stability. Photo courtesy of Big Kaiser.

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Using the appropriate cutting tools is essential to optimizing cutting conditions for cobalt chrome. According to Cetkovic, one of the biggest cutting tool considerations should be strength of the tool design. He recommends starting with a reinforced shank diameter. Choosing a milling tool geometry with a positive break angle will reduce cutting forces and deflection, which tend to be problematic with this material.

The bits themselves feature a tungsten carbide tip and a fully hardened shaft, making them suitable for drilling concrete, tiles and even granite. The four-spline SDS Plus configuration means that the bits will fit securely into your hammer drill. Importantly, all products from UK Drills are manufactured to British ISO and DIN standards.

Beyond these characteristics, cobalt chrome is heat-treatable, not magnetic, offers good hot and cold formability, and has high coefficient of thermal expansion and very high resistance to acid, making these alloys a great fit for dental equipment, medical tech, the energy sector, chemical industries, and aerospace.

Easily access valuable industry resources now with full access to the digital edition of Canadian Fabricating & Welding.

Regular masonry drills are available in diameters up to 25 or 30mm, but if you need to make a larger diameter hole – to run plumbing pipes through walls, for example – then you’ll need a masonry core drill bit. These large, hollow, cylinder-shaped bits have diamond-tipped teeth that effectively cut a circle in your masonry. Once you’ve drilled through, you’ll be left with the waste material inside the core bit. The beauty of core bits is that you’re left with a perfect hole, ensuring a snug fit.

Lindsay Luminoso, sr. editor/digital editor, contributes to both Canadian Metalworking and Canadian Fabricating & Welding. She worked as an associate editor/web editor, at Canadian Metalworking from 2014-2016 and was most recently an associate editor at Design Engineering.

Another significant consideration is that cobalt chrome is very heat-resistant with low thermal conductivity. During cutting of standard steels, heat generally is evacuated through the chip. However, with cobalt chrome, heat does not generate into the chips.

"We are able to take a lot of our more common tool geometries and apply a special coating or put a radius on the edge to help them perform in some of these more difficult-to-machine materials," he added.

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Hex drill bits are a little more unusual. The hexagonal shaft will lock into a drill more firmly, and will resist twisting in the chuck. That ensures minimal torque is lost between the drill and the drill bit. However, SDS (slotted drive shaft) bits offer all the benefits of hex, but are designed for hammer drills. A deep slot in the SDS drill bit’s shaft locks in the hammer drill’s chuck for a secure fit that won’t loosen. SDS Plus has a 10mm shank, while SDS Max measures 18mm.

Manufacturers in the orthopedic and dental implant sectors are familiar with difficult-to-machine materials like cobalt chrome. These superalloys are known for their biocompatibility, making them a great choice for medical device manufacturing. Even the aerospace industry has taken note of the unique characteristics and high degree of hardness that cobalt chrome offers. As this material becomes more mainstream, machine shops have to adapt to meet the challenges when milling this hard-to-cut material, particularly because the cost of cobalt chrome is quite high.

Suitable for wet and dry cutting through a variety of materials, the larger core drill bit is ideal for soil pipe and boiler flues, and the smaller pairing for 32mm pipe and 42mm waste pipes. This is a high-quality set that’s well-suited to any kind of major plumbing or electrical jobs.

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When it comes to drill bits, all things aren’t equal. Made from a variety of materials and designed to drill through different surfaces, masonry drill bits need to be among the toughest of the bunch.

Keep up to date with the latest news, events, and technology for all things metal from our pair of monthly magazines written specifically for Canadian manufacturers!

Doiron added that it’s not just the cutting tools themselves that an operator needs to consider. Having a rigid setup with the cutting tool fully inserted into the toolholder to the maximum depth is an optimal scenario. If an operator can keep the tool engaged in the holder to the correct gauge line, tool wear can be reduced, which is already a significant challenge even without overextending the tool.