Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.

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When looking for a set of high-quality drill bits for metal, you may want to consider the Irwin 63137 set of bits. Made from cobalt high-speed steel, they’re designed specifically for hardened steel. They have 135-degree split-point tips, helping them to resist walking when starting a hole. They also resist wear and heat, making them a solid choice for drilling through metal materials. Bit sizes range from 1/16 to ½ inch wide, and the bits larger than ⅜ inch wide have reduced shanks.

Most drill bits fit both standard corded and cordless drills. While these small pieces of metal all look pretty similar, each type of drill bit is designed to make holes in specific materials—including wood, plastic, and metal—but won’t work as well on other materials.

Paul noted the asymmetric tool’s two guide pads are positioned so they only contact the last journal, enabling the boring bar to be quickly fed in and out of the multijournal bore without touching the workpiece. This geometry allows the bar to be fed through the raw, or unfinished, bores on an eccentric path. “That is our trick,” he said, adding that the last journal functions like a counter-bearing.

Those looking for an all-around capable set of drill bits may want to check out the Bosch black oxide metal drill bit set. Manufactured from high-speed steel and coated in black oxide, Bosch drill bits can withstand friction and heat so you can drill continuously without the bits heating up.

Add a drop or two of lubricating oil to the bit and then grab the broken end of its shank with a pair of pliers. Twist counterclockwise to remove the bit.

Researching shank design, bit material, and bit coatings can be confusing, but fortunately, drill-bit manufacturers make shopping relatively easy for the customer. Drill bits are labeled not only by the size of the hole they’ll drill but also by the type of materials they’ll drill.

Home improvement centers often dedicate an entire aisle to drill bits, which come in a plethora of types and sizes for drilling holes in a variety of materials. Many drill bits can pierce through more than one type of material, but not all drill bits can drill through metal without heating up and snapping in half. Labels on drill bits indicate the type of material for which they’re suited, so it’s easy enough to find ones that are designed to drill metal. Depending on the type of metal the user is drilling through, some bits suit the task better than others.

One of the best features of the Irwin 29-piece set is the range of sizes available. Each bit increases by 1/64-inch increments between 1/16 and ½ inch, meaning there is a bit for almost any size hole.

CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

These bits are made from high-speed steel for strength, and they feature a titanium coating for reducing friction and increasing durability. The kit comes with a carrying case with a foam insert with recesses for each bit and a spring-loaded center punch for marking the holes’ locations.

Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

Some shank designs are more conducive to drilling through metal than others. Most shanks for this type of drill bit are either no spin or hex.

Look for the words “metal drilling bit” on the package, followed by a list of metals the bit is designed to puncture. Here are a few additional tips that will help drill smoother holes and keep bits in tip-top shape.

Drill bit coatings affect how a drill bit operates. Most metal drill bits are usually coated with titanium or black oxide. This coating is designed to reduce friction, which keeps the drill bit from heating up and eventually breaking. Because the coating reduces friction, it can also help increase drill speed.

These bits are made for hard use. Their construction is durable, retaining an edge while drilling through thick ¼-inch steel. The no-spin shank prevented the chuck from slipping, boring right through the metal without stopping. They also stayed cool while drilling.

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It depends on what kind of metal you’re drilling through. Titanium bits are suitable for drilling through soft metals such as aluminum, while cobalt bits are better suited for drilling through hard metals like cast iron.

While we’re not huge fans of general-purpose bits typically, especially when it comes to drilling metal, these Bosch bits were excellent. They didn’t walk when starting a hole, and they removed long shavings of metal, proving they remained sharp while drilling. We were so shocked that these bits were this good that we kept drilling with them to see if it was a fluke. They drilled holes faster than the other bits in the test, which really surprised us.

Avid metalworkers looking for a quality drill bit set for their metal projects may want to upgrade to the Irwin 29-Piece cobalt-alloy steel drill bits set. This set includes 29 drill bits from a 1/16-inch bit to a ½-inch bit, with bits larger than ⅜-inch wide having reduced-size shanks so they can fit smaller chucks.

Bits that drill through metal are further classified by the types of metal they puncture. For example, some bits are capable of drilling through ferrous metals, such as cast iron, and others through nonferrous metals, such as copper and tin.

The Bosch bits’ tapered tips can quickly penetrate the metal, balance the bit, and produce a clean, even hole. The set includes 21 bits ranging in size from 1/16 inch to ½ inch and is packaged in a plastic storage case.

Rotating cutting tool used to enlarge a drilled hole to size. Normally removes only a small amount of stock. The workpiece supports the multiple-edge cutting tool. Also for contouring an existing hole.

These are great bits, but we found they were better for enlarging holes than actually drilling them (at least when it comes to metal). If we started with another bit to drill the initial hole, we could quickly work up to the desired size with the Comoware (the tips of the bits themselves just didn’t seem sharp enough for metal). We liked that there are so many sizes in one kit, and the spring-loaded center punch worked well for locating the bit.

Kennametal reported that the asymmetric line boring bar provides a cutting speed up to 100 m/min. (328.1 sfm) and a feed per tooth of 0.2 mm/rev. (0.008 ipr) when semifinishing and 0.16 mm/rev. (0.006 ipr) when finishing and achieves a 0.005mm (0.0002") concentricity. According to Hacker, cycle time for the asymmetric line boring bar is 20 to 40 percent less when compared to reaming. Compared to “old-style” line boring, cycle time for the asymmetric line boring bar is 10 percent less.

We did dislike that the smaller bits have rounded shanks, as they can be a pain, particularly when the bit is about to drill all the way through the material. However, the large bits have no-spin shanks and do a great job of staying in place. The tips stayed sharp making hole after hole, and they remained cool to the touch during use (while using cutting oil).

First, we drilled into some relatively light-duty 11-gauge steel angle iron, testing a few bits from each pack. We wanted to see how well they’d retain their edge, how hot they’d get, and how long it would take them to bore a hole in the metal.

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Automaker BMW challenged the toolmaker to develop a tool that accentuates the advantages of reaming and line boring while virtually eliminating the disadvantages. Kennametal accepted the task and developed its asymmetric line boring bar, Hacker said.

This kit comes with 14 bits from 1/16 inch to ½ inch, all of which are made of high-speed steel. The smaller bits have rounded shanks while the larger bits have no-spin shanks. Each bit features the brand’s “black and gold” coating designed to keep them from rusting. Everything stores away in a see-through case, helping to keep the bits organized and easy to find.

Through hands-on testing, we found a number of drill bit sets that rise above the competition and help make holes in myriad metals. Some of the results were truly surprising. For those of you working on a project that requires drilling through metal, read on to learn about the factors to consider before shopping for the best drill bits for metal.

Many DIYers don’t bother sharpening their bits when the cutting edges become dull and they have trouble drilling a hole, but it’s tool maintenance worth doing. You’ll get a longer life out of your drill bits if you sharpen their cutting edges with a bench grinder.

While we don’t have an immediate use for a dozen ¼-inch drill bits, we do like that a full-time shop can order enough bits from Drill Hulk to replace their most commonly used sizes without purchasing a whole kit that contains unneeded sizes. However, we did notice that these bits can walk slightly, despite the 135-degree split point.

DIYers and pros who go through a lot of ¼-inch drill bits for their heavy-duty metalworking projects may benefit from the Drill Hulk’s ¼-inch cobalt steel set. This 12-pack of bits features jobber-style lengths, which means their lengths are relatively long compared to their diameters. They’re made from durable cobalt high-speed steel, feature 135-degree split points for drilling through metal without walking, and have a no-spin shank to prevent them from spinning in the chuck.

There’s more than one way to accurately finish a multiple-journal crank bore in an engine block. The best solution, in terms of robustness and results, is a conventional line boring bar, according to Marcus Paul, global product manager for holemaking at Kennametal Shared Services GmbH, Fürth, Germany. The finished bore has a high geometric quality because the tool is supported on both ends, but the boring process requires a special machine to lift the block so the tool can move in and out of the bore, as well as in and out of a counter-bearing on the fixture. This limits flexibility.

These bits did a fine job of drilling through our test materials. They didn’t walk when we started the holes, and they bored through the metal at a reasonable pace. The case itself has a cheap plastic tab to keep it shut, but otherwise, it does a good job of keeping these bits safe and organized. They stayed cool while drilling and retained their sharp edges even after several holes. Our biggest complaint is the rounded shank, as the small bits did spin a bit in the chuck.

To be 100 percent upfront, we have never liked DeWalt drill bits. We have found that they’re usually relatively low quality and pretty much “throwaways.” But this particular kit was incredible when it came to drilling metal. They didn’t walk at all, and they cut long, continuous, spiraled shavings—the sign of a sharp bit. The rounded shanks on the smaller bits did spin a little, but the no-spin shanks on the larger bits were great. Each bit stayed cool with a spritz of lubricant and remained sharp throughout the test. And, surprisingly, this budget kit drills through wood faster than some of the much more expensive drill bits in the test.

Most drill bits are made from HHS, cobalt, or carbide. A bit’s material can influence how effective it is at drilling through different kinds of metals.

When it comes to enlarging hotels in metal materials, a step bit like the ones in this five-piece kit from Comoware is the tool for the job. This kit features five different sets of bits, each with a series of steps, totaling 50 sizes from one kit. Sizes range from ⅛-inch to 1 ⅜-inch wide.

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It’s not a bad idea to clean drill bits after using them. After drilling, wipe away any residue on the bit with a soft cloth and then rub a bit of cutting fluid on it before storing it.

The best way to drill through thick metals is to use a drill press rather than a handheld drill—a press best achieves a clean, smooth hole. Be sure to drill slowly and use cutting fluid to lubricate the bit, too. Let the bit cool down every few minutes to keep it from overheating and breaking.

Folks who need to drill a few holes in some metal surfaces but don’t want to break the bank on a set of expensive drill bits may prefer the DeWalt DWA1184 black and gold drill bit set. This set of all-purpose bits can drill wood, plastic, or metal and features 135-degree split-point tips to help prevent walking.

The bits didn’t cut quite as fast as some of the other drill bits in the test, but they did retain their edge nicely. They also didn’t walk at all when starting the bit, and the tap size chart inside the kit could definitely come in handy. What we didn’t like was the fact that every bit, despite its size, features a rounded shank. But the sturdy case with a spring-loaded latch ensures this kit stays shut, and the rubber molding on the case can prevent it from slipping off of a work surface.

There’s only one good way to test drill bits for metal: We needed to put some holes in some metal! We grabbed some scraps of metal off our welding cart, chucked some bits into our drill, and started drilling.

Whether you’re just getting into metalwork or you want to expand that drill bit set, adding metal drilling bits to an arsenal of tools is a good investment. If drilling through metal is a new endeavor, there may be some questions that need answering.

Essentially a cantilever beam that holds one or more cutting tools in position during a boring operation. Can be held stationary and moved axially while the workpiece revolves around it, or revolved and moved axially while the workpiece is held stationary, or a combination of these actions. Installed on milling, drilling and boring machines, as well as lathes and machining centers.

We tested these Top Picks products to ensure that they had what it takes for drilling metal. To qualify as one of the best drill bits for metal, the bit needed to perform well in the metal that it’s designed to drill. Bits also need to be durable and able to withstand the friction and heat produced when drilling through metal. The following recommendations are all at the top of their class for metal drilling, and one (or more) may be an asset to your tool collection.

These drill bits are made from durable cobalt-alloy high-speed steel, helping retain a sharp edge while drilling. They all fit inside the sturdy hinged case with a spring-loaded latch to keep the kit closed when not in use. The case also has a tap guide inside to help you identify which bit to use for a particular bolt or fastener.

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Glenda Taylor is a BobVila.com staff writer with a background in the residential remodeling, home building, and home improvement industries. She started writing for BobVila.com in 2016 and covers a range of topics, including construction methods, code compliance, tool use, and the latest news in the housing and real estate industries.

The shank is the nondrilling end of the bit that fits into the drill’s mandrel or “chuck.” For hex shank bits, the shank size of the bit chosen (typically ¼ inch, ⅜ inch, or ½ inch wide) should match the chuck size of the drill.

Then we moved to some heavier-duty 7-gauge flat stock, again testing how each bit made it through the test. We did our best to maintain similar speeds and pressure throughout each portion of every test. Afterward, we did our best to hand sharpen each of the larger bits with a file. The bits that passed these tests were given awards based on their strengths.

Another option is a multiple-blade reamer with guide pads, which can be applied on a standard machining center, but the reamer’s guide pads continuously contact the workpiece, so cycle time, or machining process, is longer and chips can create quality issues if they squeeze between the pads and workpiece. “It is not as robust as the line boring bar solution,” said Michael Hacker, technical program manager for Kennametal.