Regular inspection with gage bars helps identify potential spindle problems, and can reduce downtime and spindle repairs.

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.

Toolholders with increased taper-to-taper contact, such as this Mega E collet chuck from BIG Daishowa, are useful for high-speed milling since they enable stable cutting.

A 3mm-dia., solid-carbide drill with 0.00008 " of runout produced 148 holes at 3 times diameter until the primary cutting edge experienced 0.008 " of wear, at which point tool life was considered to be over. A second 3mm-dia. carbide drill with 0.0002 " of runout under the same conditions produced just 125 holes using the same tool life measurement. The test was repeated two more times with runouts of 0.0004 " and 0.0006 ", with a decrease in tool life as runout increased.

A dynamic runout gage typically has a precise point for accurate measurement of laser alignment tools in the X and Y axes. Recent tests by BIG Daishowa of high-speed spindles showed that many machines, while accurate at 500 rpm, had runout exceeding 0.001 " at 30,000 rpm.

Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

The Mega ER Grip body has an increased contact length of the internal taper, which reduces collet overhang, and a smaller clamping range than similar products. These features improve rigidity, clamping force and runout accuracy, according to the company. The chuck system also has a prebalanced body with tapped holes around the periphery for precision balancing with screws and offers only dual-contact interfaces.

Value that refers to how far the workpiece or cutter advances linearly in 1 minute, defined as: ipm = ipt 5 number of effective teeth 5 rpm. Also known as the table feed or machine feed.

If a drill does not run concentric to its centerline, higher forces are generated in the radial direction of the highest margin, causing more wear on one side.

Shops wishing to control runout should take a close look at toolholder features such as taper-to-taper contact, as well as collet angles and corresponding clamping ranges.

Our company conducted an informal customer survey by asking, “What is good runout?” The consensus was that good runout is 0.0005 ". We decided to evaluate this benchmark using tests of various cutting tools. Figure 1 shows data from drilling tests performed at the BIG Daishowa Mega Technical Center in Awaji, Japan. Each drill was tested under the same conditions, with only runout changed for each value.

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.

• HSS tools were slightly less sensitive than their solid-carbide counterparts to diminished life. Improving runout from 0.0006 " to 0.00008 " produced a 230 percent improvement in tool life. Through-coolant HSS tools were even less sensitive to diminished tool life, producing only a 160 percent improvement in tool life.

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.

Many shops use toolholders, such as 3-jaw drill chucks, that allow drill runout to exceed 0.001 ". Extrapolating from our test data, a solid-carbide drill with runout of 0.001 " would produce fewer than 25 holes. A higher-quality chuck, though more expensive, could improve tool life dramatically.

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.

Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

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.

The BIG Mega Micro collet chuck, for holding micro cutting tools, also has a shallow taper collet angle. These collets are available in increments of 0.004 " on diameter to control runout.

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.

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.

We’re committed to testing and reviewing products so you can make an informed decision. Advertising does not influence our product reviews and it never will. We always focus our coverage on standout products and never hesitate to mention their flaws and quirks. By using our affiliate links, you’re supporting our work and helping us continue to provide expert analysis. Find out more about our product evaluation process.

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.

Machining vertical edges of workpieces having irregular contours; normally performed with an endmill in a vertical spindle on a milling machine or with a profiler, following a pattern. See mill, milling machine.

Work material1055 steelSpeed, carbide250 sfmSpeed, HSS90 sfmFeed0.004 iprHole depth, 3xD0.47 "Hole depth, 5xD0.60 "Drill diameter0.118 " (3mm)

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.

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.

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.

Work material1055 steelCutting speed300 sfmSpindle speed (rpm)2,900Feed rate0.004 "/fluteFeed46.4 ipmAxial depth0.60 "Radial step0.004 "

Articles may contain affiliate links which enable us to share in the revenue of any purchases made. Registration on or use of this site constitutes acceptance of our Terms of Service.

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 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.

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.

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.

BIG Daishowa guarantees runout of all its collets of no greater than 0.00012 " (3µm) at four times tool diameter and 0.00004 " at the nose.

Controlling runout sometimes requires a change of toolholders. For example, Ideal Tool Co., Meadville, Pa., was hard milling a 14 "×8 "×1¾ " stamping die from S7 tool steel. Runout had been from 0.001 " to 0.0015 ". After the company began using a BIG Daishowa HSK-A63 Mega New Baby collet chuck, runout dropped to less than 0.0005 ".

In a typical collet chuck system, the collet angle is 16º, which offers a clamping range of 0.039 ". However, the tradeoff to having this range is less runout control and less clamping force. For example, BIG Mega New Baby collet chucks have a 12º angle, giving them only a 0.020 " clamping range but considerably better runout control and clamping force than higher-angle chucks, according to the company. Another product, the BIG Mega E collet chuck, is for holding endmills and has an angle of just 8º, giving it even higher clamping force, rigidity and runout control.

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.

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.

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.

Image

Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

Tool materials are also critical. For example, solid-carbide drills can last much longer than HSS drills—but only if runout is tightly controlled.

Many machine shops lack objective criteria for making toolholder purchasing decisions. They say every tooling manufacturer claims high accuracy, perfect balance and large clamping forces. With so many choices and little to distinguish one toolholder from the next, most purchasing decisions are made by price alone.

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.

Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.

Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

Ideal Tool uses a Makino V55 with HSK-A63 spindle at speeds up to 20,000 rpm and feeds to 150 ipm. Like most mold shops, it runs many limited production jobs and makes numerous tooling changes. Using the new chuck, changeouts that had taken 5 to 10 minutes are completed in 30 seconds. Because the company changes out upwards of 10 chucks per job, the impact on productivity was immediate.

More concentric clamping and increased clamping force can also improve runout. For example, BIG Daishowa’s Mega ER Grip AA-grade collet chuck system is available in 2mm to 3mm diameters in 0.1mm-dia. increments, 3mm to 6mm diameters in 0.25mm-dia. increments and 6mm to 20mm diameters in 0.5mm-dia. increments. A smaller range provides a more concentric clamping of the tool shank, according to BIG Daishowa.

Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

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.

Flexible-sided device that secures a tool or workpiece. Similar in function to a chuck, but can accommodate only a narrow size range. Typically provides greater gripping force and precision than a chuck. See chuck.

This data was used to plot tool life efficiency based on average results for both carbide and HSS tools. From this data, tool life efficiency can be plotted based on runout, whereby theoretical “0” runout is equal to 100 percent tool life expectancy (Figure 2). At the “acceptable average” runout of 0.0005 ", tool life is cut in half.

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.

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.

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.

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.

The next test used the same four runout values for a 3mm-dia. HSS drill at 3 times diameter. A third test mirrored the first two, but used a 3mm.-dia. HSS drill at 5 times diameter, with through- the-tool coolant.

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.

Allowable TIR should be based on different values for tools of different diameters. Figure 4 shows the constant relationship between tool diameter and runout as a function of chip load. The data is based on 0.0005 " TIR as a starting point for a ½ "-dia. tool, from which the allowable TIR can be calculated for smaller tools and their respective chip loads. For example, if a 1⁄16 " endmill with three flutes is profiling mold steel, the effective chip load is 0.0002 ipt, which means the tool will be unbalanced when runout is 0.0005 ".

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.

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.

BIG Daishowa ran similar tests to calculate values for a 4-flute, 10mm-dia. carbide endmill (Figure 3 on page 62). Cutting length increased from 528 ' to 693 ', 1.3 times longer, as runout decreased from 0.0006 " to 0.00008 ". The reason is clear: With runout of only 0.00008 ", the cutting forces are evenly distributed on each flute, whereas with runout of 0.0006 ", an excessive force will be applied to only one flute. Less runout helps stabilize the cutting depth on each flute and produces a finer surface finish.

This BIG Mega New Baby collet chuck has a 12º collet angle, which provides better runout control and clamping force than higher-angle chucks.

• Carbide has the highest sensitivity to diminished tool life due to runout. Improving runout from 0.0006 " to 0.00008 " tripled tool life of the solid-carbide drill. Keep in mind that tool users in our survey considered 0.0005 " runout to be acceptable on average.

Image

Linear distance traveled by the cutter during the engagement of one tooth. Although the milling cutter is a multi-edge tool, it is the capacity of each individual cutting edge that sets the limit of the tool, defined as: ipt = ipm/number of effective teeth 5 rpm or ipt = ipr/number of effective teeth. Sometimes referred to as the chip load.

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.

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.

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.

Image

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).

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.

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.

Savings can be measured in cost per hole. An average price for the 3mm-dia. carbide drills used in our test is $40. With runout of 0.00008 ", this drill can produce 148 holes, or $0.27 per hole. With runout of 0.0006 ", the cost per hole nearly triples to $0.80 per hole. As a result, manufacturers willing to accept 0.0006 " runout are passing up an opportunity to cut drilling costs by 66 percent.

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.

Available in two major types: tungsten high-speed steels (designated by letter T having tungsten as the principal alloying element) and molybdenum high-speed steels (designated by letter M having molybdenum as the principal alloying element). The type T high-speed steels containing cobalt have higher wear resistance and greater red (hot) hardness, withstanding cutting temperature up to 1,100º F (590º C). The type T steels are used to fabricate metalcutting tools (milling cutters, drills, reamers and taps), woodworking tools, various types of punches and dies, ball and roller bearings. The type M steels are used for cutting tools and various types of dies.

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.

Dynamic runout gages are useful for high-speed machining. When the spindle is rotated at low speeds, centrifugal forces have little or no influence on runout. However, as the spindle speeds increase, centrifugal forces increase exponentially and can cause extreme runout.

Other influences on runout include taper-to-taper contact, and the angle of the collet and corresponding clamping range. (see sidebar on page 60).

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.

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.

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.

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.

Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.

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.

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.

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.

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.

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.

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.

Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.

Even the best collet chuck cannot deliver superior performance in an old or worn spindle. Shops should check their spindles regularly for runout using a precision gage bar. One popular gage is a simple straight bar used by slowly rotating the spindle and measuring runout with an indicator.

However, using this criteria overlooks the critical effect that runout has on machining accuracy and tool life. Many machine shops and parts manufacturers are not aware they can improve runout significantly by using the right toolholders.

Two important variables in determining acceptable runout are tool size and composition. With tools 3⁄4 " in diameter or larger, runout of 0.0005 " may not impair performance and tool life. However, with smaller tools runout may need to be much better than 0.0005 ".

About the author: Jack Burley is vice president of sales and engineering for BIG Kaiser Precision Tooling Inc., Hoffman Estates, Ill. He has more than 25 years of experience in metalworking and has been with BIG Kaiser since the founding of its U.S. operations in 1990. Contact him at (847) 228-7660, ext. 111, or by e-mail at jburley@bigkaiser.com. For more information about the company’s products, enter #350 on the I.S. Form.

What many shops believe is acceptable runout is actually unacceptable if the shop wants to improve tool life. A manufacturer basing toolholder purchase decisions solely on the price of the toolholder may end up choosing a more expensive alternative, based on tool life and cost per hole, while sacrificing quality and accuracy. CTE