Here’s how leading tooling manufacturers are helping customers put these tools to work in machining titanium, nickel-based alloys, superalloys, Inconel and stainless steel.

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When folks have a variety of different tile materials to tackle, it can be difficult to pick the best drill-bit set. In our tests, this 10-piece set of masonry drill bits from Owl Tools demonstrated a high level of durability while the spear tips proved to reduce wandering (sliding across the surface of glazed tile before creating a hole). The shanks are made from steel and the bits boast carbide tips for added hardness.

Stusak emphasized the benefits of these machining strategies by explaining that the basic principle of metal cutting is forming a chip properly in relationship to edge geometry so that you are shearing the material, not plowing it. Both roughing and finishing benefit from optimized machining strategies, but especially roughing, where machining time can be greatly reduced.

Drilling in glass tiles is more straightforward than it might seem—a good carbide-tipped blade is essential, as is using a slow drill speed. The four-piece bit set from Bosch excelled in our glass-drilling tests.

Cutter paths vary and can include profiling, slotting, and pocketing. Workpieces can vary in complexity and size as well. YG-1 has tools for specific materials like titanium, Inconel or aluminum as well as general-purpose tools for smaller shops and multiple applications.

Horn’s solid-carbide tools with seven or nine flutes with large DOCs and 10-15 percent stepover—as a rule of thumb to start with—help with these strategies, but the machine tool must have the required acceleration and deceleration. An older machine with rapids of 600 ipm will not be sufficient. Similarly, the look-ahead that newer machines have is also required.

These optimized high-speed and high-efficiency machining strategies are the wave of the future. And they are here today. According to Ball, 80-90 percent of CAM software suppliers have some sort of optimized milling strategy for roughing and 80-90 percent of the major cutting tool manufacturers have some sort of multi-flute products for these strategies.

With high-temperature-resistant, nickel-based alloys being used more commonly by its customers, Seco Tools LLC, Troy, Mich., is focused on maximizing metal removal rates using high-speed, high-efficiency optimized roughing strategies, according to Jay Ball, solid-carbide product manager.

The set comes with bits ranging from ⅛ inch to ⅝ inch in diameter and from 2 inches to 2¼ inches long. Each bit features a spear tip with a sharp point the manufacturer claims will keep the bit from wandering. Unfortunately, we found each one of the bits tended to wander on the glass tiles unless we used masking tape—an easy fix that didn’t detract from the bits’ performance and durability. Wandering is common when drilling through tiles, so everyone should be prepared to use tape.

After drilling 10 starter holes, we examined the spearheads of the bits. The two smallest bits showed substantial dulling and wear on the blades, so we set those aside and continued with the other five. None of the other bits made it past 25 additional holes, so we can’t rate the Qwork bits as the most durable of the ones we tested. Perhaps the steel wasn’t quite as high in quality—but we still deem these bits to be a decent option for jobs that require metric bits and fasteners, since those are typically small projects, such as installing a towel bar or a ceramic soap dish. And interestingly, these bits didn’t wander much, not even on un-taped glass, so they earned a point in that department. Consider these as light-duty tile-drilling bits for metric usage.

YG-1 has developed standard tools specifically for high-speed machining of titanium, but about 30 percent of its tools for this application are still custom made, with special lengths and corner radii. “One of the trends with high-speed machining is the increased number of flutes needed to take light cuts and run very fast,” he said. “The trend of the last five years is for five, six, seven and nine flutes,” he said. The advantage is longer tool life and better heat and chip control as well as machining performance.

Diamond-tipped drill bits are recommended for porcelain. The bits can get very hot, so dipping them in water occasionally, or spraying the area while working, will keep them cool and help them cut more effectively.

Drill bits are labeled by the diameter of their shanks. The smallest drill bits for tile are usually around ⅛ inch in diameter. The biggest twist drill types are seldom more than ½ inch. When drilling in hard tile, it can be difficult to control large bits (more than ¼ inch) on shiny, glazed surfaces, so it’s common practice to first drill a small “pilot” hole and then follow up using the larger bit.

He added: “We have started to play a lot more with variable indexes and [helixes] in multi-flute cutting tools because of their potential for more cutting pressure due to increased tool contact with the workpiece. However, it’s necessary to change [helixes], rakes and indexes to vary the geometry in such a way that it breaks up chatter and harmonics and still retains the tool’s ability to cut efficiently.”

Bob Beacham is an engineer by trade and has spent 35 years working on everything from auto parts to oil rigs. He is also an avid DIY enthusiast. Bob started writing for the Bob Vila team in 2020 and covers tools, outdoor equipment, and home improvement projects.

The end mills are available in four geometries: barrel-shaped, oval form, taper form and lens shape. Oval and taper form mills are suited for curved shapes such as blades or straight-walled pockets, freely engaging more of the cutting edge. Barrel design mills provide effective flank milling to the sides of spiral grooves and similar applications, according to Emuge. Lens-shaped mills excel in narrow channels or in lands on molds. Specific CAM systems software, such as Mastercam and hyperMILL, are required to support and compute the geometries.

After 10 holes, we inspected the bits. The largest one showed a slight amount of wear on the edges of the spear blades, while the others looked nearly new. They all went on to drill 30 more holes apiece, but toward the end, they made slower progress, and we had to exert more pressure on the drill. Fortunately, we didn’t have any cracked glass tiles after all the drilling. That’s largely due to the sharpness and durability of the bits, but we also give a little credit to an old computer mouse pad that we placed beneath some of the tiles as we drilled, which absorbed some of the vibrations and may have helped prevent cracking.

We had high hopes for both Neiko’s Diamond Hole Saw Bits and Blendx Diamond Drill Bits, but they didn’t live up to our standards. Both of these bit sets are marketed as having diamond dust electroplated on the edges of the bits, and porcelain was listed among the types of tile they would cut through.

He pointed out that while getting material roughed out is difficult and can cause multiple problems, optimized roughing with 6-10 percent maximum radial stepovers is effective on heat-resistant superalloys (HRSA) and titanium. “And you can use these same tools to then finish a lot of these parts as well so you are using more traditional side mill finishing,” he said.

The advantage of multi-flute end mills is that operators can take higher feed rates because of the reduction in DOC and stepover with high-temperature, heat-resistant materials. “These metals don’t like to be machined in the conventional way with large DOCs and large radial stepover and slow feed rates,” said Ball. “Multi-flute tools allow increased MRRs without work hardening because you can run faster feed rates and lighter radial stepovers with more teeth.”

We’re well aware of the superior quality of many DeWalt power tools and accessories, so it was no surprise that the company’s seven-piece set of masonry drill bits excelled at drilling through tile. The set features bits ranging in diameter from 3/16 inch to ½ inch with lengths ranging from 3 inches to 6 inches. Three of the bits are ¼ inch, which is a commonly used size.

Using the right drill bit is critical. Standard drill bits will not cut through the tiles; attempting to do so is likely to cause cracked tiles and broken bits. Use masking tape to mark the position of the hole, which will also provide initial grip for the bit. Hold the drill firmly and apply slow, steady pressure. If you also need to drill the masonry or concrete behind the tile, do not use a drill’s hammer action until you are through the tile.

The most common tip coating is tungsten carbide (often just called carbide), which is a combination of tungsten and carbon. Tough and heat-resistant, carbide-tipped bits stay sharp for longer.

These proved to be very durable heavy-duty bits: After drilling 10 holes with each, we saw virtually no softening of the blades or dulling. As we drilled an additional 30 holes per bit, we still didn’t notice much slowing down. The deep flutes in the shank quickly removed the powdered tile material as we drilled, and the holes were clean and uniform.

For holes larger than ½ inch in diameter, a hole saw (or hollow core bit) is often recommended. A hole saw bit features a circular ring of HSS, usually with a diamond-coated edge. Hole saws can be large enough to allow for the fitting of plumbing pipes, for example. However, some have limited depth, so it’s crucial to check the dimensions before purchase.

Understanding the composition of these materials is key to understanding the limitations with cutting speed. “Workpiece hardness and material composition have a huge bearing on machinability,” he explained. “Nickel-based, cobalt-based, and ferrous-based superalloys have certain alloying elements in them that won’t allow elevating the sfm because you can’t eliminate the heat in the cut no matter what you do with the width of cut or cutting speed. [Cutting speeds have] to stay between 80 to 110 sfm depending on the hardness of the material.”

While our main objective in testing these bits was to determine their performance on glass, we also tried them afterward on a marble tile and a travertine tile. At this point, the bits were slightly worn down but still drilled through both materials cleanly, albeit slowly.

“All four of those strategies are essentially the same,” said Stusak. “We have developed multi-flute tools, and specifically a seven-flute tool with chip splitting technology to allow very light widths of cut depending on the length of the flute on the end mill. These strategies actively manage all four of the attributes in the CAM systems—including the radial width of cut, the arc of contact, chip thickness and the feed rate—for optimized performance,” he said.

According to the company, time and cost savings and increased part quality result. Tool life is increased due to shorter toolpaths. Tolerance deviations due to heat warping at the tool are minimized, and axial deviations of the machine are smoothed, offering a higher quality surface finish in a shorter time frame. Circle Segment end mills feature unique forms with large radii in cutting areas of the mills, allowing a larger axial DOC during prefinishing and finishing operations.

“In evaluating machining for large aerospace parts, for example, while I’m not a programmer, in most cases I can look at the program and tell what ought to be changed,” said Bruhis. “In the last few years between traveling and working all over the world, if I can’t review the program, I have my customer send a video of the simulation and hold an online meeting to discuss possible program modifications. Through Skype interactions, I do simulations and alter programs constantly.”

It’s important to have the right CAM software to avoid wasted rapid travel movement, which increases cycle time. There are times when it is better to take a more conventional cutting pass. One example is when the width of cut is short with, say, a 0.5" (12.7-mm) end mill with the intention of cutting a length of the part that’s 0.5" long and the process needs to remove 0.3" (7.62 mm) of material. In this example, Horn recommends taking all the material off in one or two passes instead of 30 passes. To be efficient, the tool must stay on the part and limit time-wasting retraction.

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The highest MRR possible in high-speed machining with multi-flute tools occurs when the process engages the full flute length of the tool. The more flutes, the larger the core diameter for rigidity. Typically, the first thing to look at when considering high-speed machining is the size of the part and flute length to decide the diameter of the tool, according to Horn. An inch of actual flute length might be handled by a 3/8" (9.5-mm) diameter tool, and two inches of actual flute length by a 5/8" (15.8-mm) diameter tool.

A less common coating is the powdered form of industrial diamonds (usually called dust), which is fused to the drill bit via an electroplating process under tremendous heat and pressure.

The ECI-H4S-CFE end mill is a short, four-flute design with different helixes (35o and 37o) and variable pitch for chatter dampening. It can be used for high MRR roughing and finishing, with full slot milling up to 1×D. It is also available with the new AlTiCrSiN IC608 coating for machining at elevated temperatures.

Whether for drilling wood, metal, masonry, or tile, the shanks (stems) of almost all drill bits are made from high-speed steel (HSS). Though a hard-wearing, relatively inexpensive material, HSS can lose its sharpness quickly when drilling hard materials like stone and ceramic tile, so the tip of the bit will be given a coating to make it harder and more durable.

These machining strategies require more just than the right carbide grade, insert and geometry—the way of approaching the material is also critical. The goal of high-efficiency machining is to reduce the width of cut and increase the length of cut to reduce cutting forces, which allows faster machining. Sometimes it is quicker that way, and sometimes it is quicker using traditional high-feed cutters. Many times with dynamic machining there can be much wasted movement. Applying it depends on the application and complexity of the features, such as pocketing, that are involved.

Whatever you are drilling, you should wear suitable eye protection. If you usually wear glasses, put goggles on over them. A lightweight dust mask is also a good idea.

“When major OEMs call me in, it’s generally to improve tool life, the process, or both,” Bruhis continued. “It could be a new project with them facing a serious issue. It might be a problem with part quality, or cycle time or delivering parts in time or total cost, but it’s almost never because of the cost of the tool since YG-1 offers a very attractive performance-to-cost package.”

Porcelain has a finer texture, but it can be difficult to tell the difference if the tiles are already on a wall. Ceramic tile usually has a glazed top layer that is a different color from the core, which may show at the edge. Porcelain is usually the same color throughout.

Not every part is a good candidate for high-speed machining. The choice of strategy is a function of the part geometry and size. Some of the testing that’s being seen has been calling for machining Inconel, titanium, and stainless with light depths of cut, high speeds and low radial engagement and feed rates.

Chip-splitting technology reduces the radial tool pressure encountered with long lengths of cut and helps break up the chips, producing more manageable chips for the operator or the chip pan or conveyor to remove, Stusak explained. “The key to machining difficult-to-machine materials is the radial engagement,” he said. “You want to minimize the width of cut or arc of contact to beat the heat.” By minimizing the width of cut, not as much heat transfers into the tool because of the limited amount of cut time on the end mill.

If only one or two holes are required for a particular job, buying a single drill bit can be an economical option. However, depending on the bit type, an individual bit can cost several dollars. If drilling tile is likely to be an ongoing task, a drill-bit set may be a smart investment. A set typically includes several bits in various sizes.

“We determine the process and program and run it within a range of speeds and feeds and estimate a cycle time,” Bruhis said. “Once the customer has a chance to run the program that we have set, we then can get feedback with real machining time results and, if the cycle time is too long and the cost is not in line with expected results, we make the required adjustments.”

With a growing number of kitchen and bathroom fixtures now supplied in metric sizes, it may be necessary to have an accurate metric drill bit for tile. Imperial (United States) equivalents are close but not always close enough. In the past, we’ve had to guess which Imperial bit or anchor is most comparable to the metric one called for, so we were excited to test these carbide-tipped metric drill bits.

If it’s a very shallow “depth of part,” the machinist will not get the economy of the end mill and high speed and will experience a lot of excess vibration. The reason is if a shop runs a shallow axial depth of cut, it reduces MRR and the operation may not be as efficient as other methods with larger radial and shallower axial stepovers.

The following drill bits are all suitable for drilling in tile, but some are better suited to one type of tile than another. Each was tested on the type(s) of tile recommended by the manufacturer or seller, but not all the bits we tested earned a spot in this lineup. Find out the pros and cons of each of the following bits and bit sets before selecting the best option for your tile-drilling project.

Alas, it was not to be. Both the Neiko bits and the Blendx bits cut through ceramic, travertine, and even glass tile, but every bit in both sets pooped out before creating a hole in porcelain tile. Since porcelain is extremely hard, we always tried the bits on softer types of tile before drilling through porcelain—that way, we knew what they would drill as well as what they wouldn’t. None of the Neiko or Blendx bits got more than halfway through porcelain before the diamond dust burned off. And that was even with water droplets added to the holes as we drilled. In short, neither of these products qualifies as being among the best drill bits for hard porcelain tile.

A carbide-tipped drill bit is usually recommended, although a diamond-tipped one will also do a good job. To attach a fixture, such as a towel bar, to a tile wall, it’s always necessary to drill a hole first, after which the drill can be fitted with a screwdriver bit for installing a fastener in the wall.

Diamond bits are among the only ones suitable for drilling into porcelain or quarry tile, both of which are extremely hard. Unfortunately, some diamond bits on the market claim they will drill through porcelain tile, but as we discovered in our hands-on testing, they fail. In other words, not all diamond bits live up to their seller’s claims.

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With the largest ½-inch bit, we did crack two glass tiles, but we feel that was primarily due to our wrists and arm muscles becoming fatigued and not holding the drill as stable as we should have. A few days after the original test, we tried again and drilled through glass tiles with no cracking. We feel these DeWalt bits fit the bill for professionals needing durable bits on the job.

“Processing these materials with conventional machining processes tends to work harden them,” he explained. “Using high-efficiency milling and optimized roughing, there is a lot less heat generated because you are taking lighter radial stepovers and depths of cut (DOC), but not putting a lot of heat into the workpiece,” he said. “Where the typical solid-carbide end mill used for roughing and finishing typically had four and five flutes, with high-efficiency milling now taking over the industry we have added six-, seven- and nine-flute tools.”

We tested the Owl Tools bits on several types of tile, including marble, travertine stone, shale, glazed ceramic, and glass tiles. We used masking tape on some of the tiles to further reduce the risk of wandering and prevent surface chipping, but we also drilled holes without the benefit of tape, and the Owl Tools bits excelled in both cases. We drilled all the test holes without adding drops of water because the bits were drilling so well dry, we didn’t feel water was needed.

Glenda Taylor is a product tester and writer specializing in the construction, remodeling, and real estate industries. She and her husband own a general contracting company, and Taylor is experienced in both residential and commercial building applications. She tests a wide range of power tools as well as other home improvement, household, and lawn-and-garden products.

You can, but the grout is a relatively soft material, and the drill bit can easily wander. For accuracy, drilling through tile is usually preferred.

Over the years, we’ve had plenty of practice drilling tile, so our experience combined with in-depth product research was instrumental in selecting the drill bits for testing. We considered the brand to an extent—DeWalt and Bosch are both top manufacturers of construction tools—but didn’t automatically eliminate drill bits from smaller or niche manufacturers if they featured carbide or diamond tips and were rated well by consumers.

Another advantage to the Owl Tools set is the number of different-size bits. The set includes 10 bits that range in diameter from ⅛ inch to ½ inch in both 4-inch and 6-inch lengths, making this tile-drilling bit set suitable for drilling a range of hole sizes in several common types of tile.

We could still recommend these bits as suitable for drilling through ceramic and glass, but because they failed on porcelain, we had to eliminate them from the competition. One of our testing criteria is ensuring the products we test live up to their marketing hype. It’s not that these are bad bits, but both were advertised as being suitable for porcelain, and neither lived up to that claim.

We used the DeWalt bits to drill through travertine, slate, marble, ceramic, and glass tiles. The bits have carbide spiral tips, and we tested them with and without masking tape. They wandered less than we expected, even without tape, but we would suggest taping highly glazed ceramic and glass tiles to be on the safe side.

The ECP-H7-CF multi-flute (seven flutes) end mill has a hard substrate, IC902 ultra-fine carbide grade with 9 percent cobalt, and is TiAlN PVD coated. It is suitable for machining various materials, including hard steel and cast iron, at high cutting speeds, according to Iscar.

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The goal is to maximize flute length because that’s what will provide the best MRR in combination with 5 and 10 percent stepovers. Another way to determine tool selection is to decide whether to simply switch to high-feed milling and ramp in with a conventional end mill and rip the stock out.

There are other advantages. “By minimizing the width of cut you can elevate the surface footage on most alloys, with the exception of nickel-based alloys,” said Stusak. “You can’t elevate cutting speed that much because it is impossible to eliminate the heat in the cut, but for Ti6Al4V we have case studies where we have machined up to 400 sfm at 4 percent radial engagement with these tools.”

He also noted that the trend in titanium alloys and exotics machining in the last four or five years is toward high-speed machining for medium to large parts because the cost of removing titanium or Inconel is much higher than that of aluminum or steel.

Our actual testing process was straightforward. All of the drill bits were tested using a standard cordless drill. We used masking tape on the tops of some tiles, which can help keep bits from wandering and reduce the risk of the tile chipping during the drilling process. It’s not always necessary, so we didn’t tape all the tiles—for example, the surface of a travertine tile is soft and porous, and most bits will not wander when drilling through travertine. As the manufacturer suggested—or if a bit was struggling to drill through—we added a few drops of water while drilling to help keep the bit from getting too hot and breaking.

Cycle times for five-axis machining of molds, blades and other complex aerospace and medical parts can be reduced up to 90 percent with Circle Segment solid-carbide end mills, according to Emuge Corp, West Boylston, Mass. While manufacturers performing high-speed machining may be familiar with using traditional ball nose end mills to make small stepover passes, Circle Segment end mills use high stepover passes up to 10 times greater than ball nose end mills to cut out large areas of material, maximizing efficiency and minimizing cusp height.

Seco Tools has developed specific geometries, coatings, carbide substrates and edge preps for these difficult-to-machine materials. The company’s latest development in coatings is its patented HXT silicon-based coating for higher thermal resistance and abrasion resistance. “What we have found is that these same tools can be used to cut easier-to-machine metals such as tool steels, stainless steels and cast iron. So we’re now able to use these high-efficiency milling strategies to increase tool life and productivity on a broader range of easier-to-machine materials,” said Ball.

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The material tile is made of will impact drill-bit choice. Fortunately, most drill bits list the types of tile they’re designed for on the package or product description.

After drilling more than 45 holes, the Hillman bit started to slow down, and we could see that the tip was softening and wearing down some. However, we felt its performance and durability were still good under pressure, and the bit never broke. A single-size bit won’t be suitable for all tile-drilling purposes, but it’s more economical to buy just one if only drilling a few holes of the same sizes.

The following is a consensus report of an interview held with Tonne, Eric Carbone, application and sales engineer; John Kollenbroich, head of product management; and Jeff Shope, application and sales engineer.

Advanced cutting tools can maximize metal removal rates (MRR) when machining even the most difficult-to-machine materials. Powered by the latest CAM programs, these machining strategies are known variously as high-speed, high-efficiency, optimized roughing and also by proprietary brand names like Mastercam’s Dynamic Milling. Tools such as multi-flute, solid-carbide tools benefit from the latest advanced technologies in machine look-ahead, high-speed spindles, coatings and geometries.

We scored each bit (or bit set) using a rubric throughout the hands-on testing process. The better a drill bit performed, the higher the score. We looked for durability and relatively smooth-edged holes—it’s not unusual to have some slightly ragged edges, however. We did not judge the bits on how long it took to drill through a tile because different types of tile require longer drilling times, and it’s counterproductive to exert strong pressure while drilling as it can cause the bits to break. After drilling an initial 10 holes with each bit, we inspected them for dulling and wear before drilling more holes.

Besides the component, programming strategy and software play into this as well. If a shop is performing high-efficiency or high-speed milling, it must have the horsepower and torque required to drive the tool. If it runs the wrong software, there will be a lot of costly, wasted moves.

Many drill bits might appear similar at first glance, but the best drill bits for ceramic tile are very different from the best drill bits for hard porcelain tile, wood, or steel. In addition to selecting the right bit for the type of tile, there are a few other considerations, such as tip shape and whether the tip comes with carbide or diamond-dust coating.

When a project requires only a few holes to be drilled in tile, consider buying a single bit rather than a whole set, such as this Hillman Tapper drill bit in a 3/16-inch diameter and 3½-inch length. (We chose that size to test because 3/16-inch is a fairly standard hole size for installing towel rods and toilet-paper-holder anchors). We drilled holes in marble, travertine, slate, glass, and ceramic tiles with this carbide-tipped spiral bit. We did use masking tape for most of the holes because the bit had a tendency to wander without it. The bit drilled clean holes in ceramic and stone tiles but seemed to struggle on the glass tile, so we added a few drops of water to the hole to help cool the bit and reduce friction (not cooling a hot bit is a primary cause of bit breakage).

We tested the bits by drilling multiple holes, but we only tried them on tile types they were designed for. In short, we did not test a bit made for drilling ceramic or glass tiles on porcelain tiles, which are much harder. Our goal was to determine how well the bits stood up to their intended drilling purposes.

It is different with PH stainless, some duplex stainless steels, and titanium alloys where speed can be increased to get more productivity out of the tool. “Duplex stainless steels that have a lot of nickel and chrome content machine more like Inconel materials because of the high nickel content. So, it’s essential in machining high-temperature alloys to understand the alloying elements in them,” he said.

The ECY-S5 end mill with five flutes features a general-purpose substrate and AlTiCrSiN coating (IC608) for shoulder or full slot high-speed milling or trochoidal or peel milling. Its primary application is stainless but it can also be used to machine nickel-based, high-temperature alloys.

When drilling through tile, it’s best to go slowly and use only light pressure on the drill bit. Don’t try to force the bit through—let the drill and the bit do all the work. If you still have questions about selecting and using the best drill bits for tile, keep reading for answers to some commonly asked questions.

“I talk to a lot of people in aerospace and the trend has changed in the last 10 or 15 years,” Bruhis continued. “It’s not the cost of the tool any more. Customers want to know the real cost of metal removal. There are a lot of cases where I meet with engineers or programmers and they clearly voice that they do not care about the price of the tool. Cycle time and tool life are the most important considerations.”

Horn’s DSFT end mills—part of the DS line of high-DOC, low-radial-engagement tools—are designed for trochoidal machining. To be effective, DS tools require a solid machine spindle with close runout and a capable controller for programming. CAD programs are available to create simulation of machining time estimates to decide whether traditional end milling or high-speed machining is best. In addition, there are a number of software tools available to evaluate the economics of these tooling decisions.

The ECKI-H4R-CF four-flute end mill features corner radii for aerospace applications and either of two coatings, IC300 TiCN or IC900 AlTiN. It offers variable pitch and variable helix and a special edge prep for machining titanium.

Removing metal is important, and doing it fast enough to make money is more important. To capitalize on the latest machining strategies for milling difficult-to-machine materials, Iscar Metals Inc., Arlington, Texas, continues to add to its lines of multi-flute, solid-carbide end mills, according to Bryan Stusak, national product manager–milling. Iscar has designed solid-carbide end mills specifically for milling strategies, including high-speed milling, high-efficiency milling, optimized roughing and proprietary CAM strategies like Mastercam’s Dynamic Milling.

After drilling 10 holes, we checked the bits for wear. The carbide-tipped spears were still sharp, and none of the bits had broken. After 30 more holes in various types of tile, we noticed the bits (we tested one of each size) were starting to drill slower. Upon inspection, we found the spear tips were beginning to wear down—but we still consider that superior performance for drilling about 40 holes in hard tiles.

Drilling holes in tile—to install towel rods in a bathroom renovation, say—can be tricky. There’s always a risk the tile will crack, especially if you use the wrong drill bit. What’s more, attempting to drill tile with a standard steel bit designed for use on wood can cause the bit to overheat, bend, or even break in half. Of course, with the right bit, drilling tile can be nearly as straightforward as drilling wood—and since most tile drill bits and drill-bit sets are fortunately affordable, it makes sense to have the right tool.

However, tile is made from various materials, so it’s crucial to select the right bit for the specific material. To help DIYers and pros alike get great results, we tested some of the best-rated designated tile bits, creating holes in ceramic, porcelain, marble, glass, and stone tiles. As we expected, some performed better on one type of tile than another. Our favorite was the Owl Tools 10-Piece Masonry Drill Bit Set for its impressive durability and wide range of sizes to meet most tasks. Ahead, learn about drilling in different types of tile and find out how the following bits earned a spot on our lineup of the best drill bits for tile.

“Finishing is typically done with a 45o helix end mill for hardened materials up to 65 HRC because the higher helix angle shears the material more effectively,” he said. “End mills with a 60o helix angle are used on nonferrous materials like aluminum and even high-nickel-content alloys in finishing applications. In general, a variable pitch end mill with a 35 to 38o helix angle is the most common we see in the industry because it has a good balance of edge strength and core diameter, and it’s a little bit more up sharp in the cut where it slices through the material more effectively vs a 30o helix end mill.”

Like other companies contributing to this article, Horn USA Inc., Franklin, Tenn., stresses both the importance of multi-flute tool design and customer collaboration for tooling success. “I would describe us as an engineering-driven company that approaches tooling solutions for its customers with finesse,” said Edwin Tonne, training and technical specialist. Horn, which is well known for its grooving and cut-off turning tools, offers a broad line of products, including solid-carbide end mills, drills, and indexable milling cutters, as well as its turning products. More than 40 percent of its cutting tools are specials. Horn has developed multi-flute end mills used to machine titanium, Inconel, stainless and other high-temperature-resistant metals using high-speed and high-efficiency machining strategies to achieve the highest MRR.

The two most common shapes for tile-drilling bits are spear and spiral. Spear tips look like small arrows, and while they have the sharpness needed to create precise holes, their narrow shape makes them less durable and more likely to break. Spiral tips have a flat blade along the top with a little point in the middle that helps the user center the hole. Spiral tips are typically more durable but—depending on the tile—can take longer to complete the hole. In general, spear tips are better suited to softer tiles, such as travertine, marble, or ceramic, while spiral tips are less likely to break when drilling harder tile materials, including quartz and granite.

Bruhis described how he evaluates and determines an approach to a titanium machining project. “I typically inquire first about the machine capability, whether three-, four-, or five-axis, vertical or horizontal, fixturing and tooling,” he said. He added that in the majority of cases, specific end mills are selected based on axial or radial cut, speeds and feeds, and programming for high-speed and high-efficiency machining.

The objective of both high-speed and high-efficiency machining strategies is to improve MRR, according to Yair Bruhis, global product and application manager for YG-1 Tool Co., Vernon Hills, Illinois. High-efficiency machining increases cutting by limiting air cutting time. “Because the two machining strategies are so effective, people want to switch everything towards them,” said Bruhis. “But it all depends on the part and the machining parameters. Sometimes, I can look at the part and state that it can’t be machined with high-efficiency strategies because of the shape and complexity of the part, or the machine’s capabilities, or the part features and programming, among other factors.