You’ll need a drill press to use this tool safely, but for holes larger than a Forstner can manage, you can’t beat a circle cutter. Infinitely adjustable for diameters up to 6", this big-hole specialist replaces a pile of expensive holesaws, for example, and cuts cleaner, smoother holes in the bargain. Use it to cut snug-fitting openings for vac hoses in shopmade jigs, fences, etc. As a bonus, you can invert the cutter to create toy wheels and other perfect disks. The cutter is also very easy to sharpen. To use a circle cutter safely, choose a low speed on your drill press, clamp down the work, keep your fingers clear, and feed the tool slow and steady. You’ll be amazed at the results.

Drill bits are the cutting tools of drilling machines. They can be made in any size to order, but standards organizations have defined sets of sizes that are produced routinely by drill bit manufacturers and stocked by distributors.

The gauge-to-diameter ratio is not defined by a formula; it is based on—but is not identical to—the Stubs Steel Wire Gauge, which originated in Britain during the 19th century.[2] The accompanying graph illustrates the change in diameter with change in gauge, as well as the reduction in step size as the gauge size decreases. Each step along the horizontal axis is one gauge size.

Twistdrill bit

In the U.S., fractional inch and gauge drill bit sizes are in common use. In nearly all other countries, metric drill bit sizes are most common, and all others are anachronisms or are reserved for dealing with designs from the US. The British Standards on replacing gauge size drill bits with metric sizes in the UK was first published in 1959. [citation needed]

Stopped holes, sort of. A spade bit can drill a stopped hole, but the long center spur leaves a deep, narrow hole in the middle.

Bestdrill bit that makes holes

Extended-reach or long-series drills are commonly called aircraft-length from their original use in manufacturing riveted aluminum aircraft. For bits thicker than a minimum size such as 1⁄8-inch (3.175 mm), they are available in fixed lengths such as 6, 8, 12 or 18 inches (152, 203, 305 or 457 mm) rather than the progressive lengths of jobber drills.

StepDrill Bit

The term jobber refers to a wholesale distributor—a person or company that buys from manufacturers and sells to retailers.[citation needed] Manufacturers producing drill bits "for the trade" (as opposed to for specialized machining applications with particular length and design requirements) made ones of medium length suitable for a wide variety of jobs, because that was the type most desirable for general distribution. Thus, at the time that the name of jobber-length drill bits became common, it reflected the same concept that names like general-purpose and multipurpose reflect.[citation needed]

Drill bit sizes are written as irreducible fractions. So, instead of 78/64 inch, or 1 14/64 inch, the size is noted as 1 7/32 inch.

The price and availability of particular size bits does not change uniformly across the size range. Bits at size increments of 1 mm are most commonly available, and lowest price. Sets of bits in 1 mm increments might be found on a market stall. In 0.5 mm increments, any hardware store. In 0.1 mm increments, any engineers' store. Sets are not commonly available in smaller size increments, except for drill bits below 1 mm diameter. Drill bits of the less routinely used sizes, such as 2.55 mm, would have to be ordered from a specialist drill bit supplier. This subsetting of standard sizes is in contrast to general practice with number gauge drill bits, where it is rare to find a set on the market which does not contain every gauge.

Drill bit that makes holesfor metal

Contrary to popular wisdom, Forstner bits can be used with handheld drills, but be sure to go in straight and square and start with a light touch. Forstner bits can bore deep holes, but you’ll need to withdraw the bit frequently to clear chips and help prevent overheating. The same geometry that cuts clean-sided holes puts a lot of steel in contact with wood, producing extra friction. If your bits will be subjected to heavy use, consider spending the extra money for carbide Forstners that can take the heat without getting dull.

A holesaw won’t cut as cleanly as a circle cutter, but it can make holes just as big. You can use these bits in a handheld drill, but make it a powerful one. These hefty bits demand high torque and a firm grip. In my tests, I found that holesaws with fewer teeth—and long slots ahead of those teeth to eject chips—cut worlds better than those with continuous teeth around the rim. Like circle-cutters, holesaws can only drill through holes, in materials up to about 2" thick. If you don’t own a drill press, or you are facing a remodeling job that requires big holes in construction lumber, a holesaw is right for you. Holesaws equipped with “bi-metal” or carbide teeth can also drill through thin metal.

Jobber-length drills are the most commonly found type of drill. The length of the flutes is between 9 and 14 times the diameter of the drill, depending on the drill size. So a 1/2 in (12.7 mm) diameter drill will be able to drill a hole 4+1/2 in (114.3 mm) deep, since it is 9 times the diameter in length. A 1/8 in (3.175 mm) diameter drill can drill a hole 1+5/8 in (41.275 mm) deep, since it is 13 times the diameter in flute length.[3]

In smaller sizes, bits are available in smaller diameter increments. This reflects both the smaller drilled hole diameter tolerance possible on smaller holes and the wishes of designers to have drill bit sizes available within at most 10% of an arbitrary hole size.

Types ofdrillbits for metal

I tested a variety of Forstner bits; some had wavy teeth around the rim, while others had straight teeth or simply a sharp bevel. The performance differences I noticed were slight, with mid-priced Forstners performing as well as more expensive versions. To get the most for your money, buy a set of Forstner bits instead of acquiring them individually.

Fractional-inch drill bit sizes are still in common use in the United States and in any factory (around the globe) that makes inch-sized products for the U.S. market.

To solve the big bit puzzle, I ordered a bunch of plus-sized bits and collected plenty of wood to use for various drilling assignments. You’ll find plenty of helpful information in the chart on the facing page, and in the write-ups that follow. With these details, you’ll be able to match the bit to the job and get the best value from every bit of money you spend on these tools.

ANSI B94.11M-1979 sets size standards for jobber-length straight-shank twist drill bits from 1/64 inch through 1 inch in 1/64 inch increments. For Morse taper-shank drill bits, the standard continues in 1/64 inch increments up to 1¾ inch, then 1/32 inch increments up to 2¼ inch, 1/16 inch increments up to 3 inches, 1/8 inch increments up to 3¼ inches, and a single 1/4 inch increment to 3½ inches. One aspect of this method of sizing is that the size increment between drill bits becomes larger as bit sizes get smaller: 100% for the step from 1/64 to 1/32, but a much smaller percentage between 1 47/64 and 1 3/4.

In any workshop or homeowner’s toolbox, you’re sure to find a good selection of small bits—a set of standard twist drills and, if you’re lucky, a full set of brad-point bits also. But that bit kit tends to peter out when you get to larger diameters, let’s say ¾" or greater. There are plenty of tasks that require big bits (sidebar, right), but it’s not always easy to choose the bit you need, because of the bewildering array of types available.

With a lead screw that keeps them on track and pulls them through the wood, plus deep flutes for ejecting chips efficiently, auger bits drill deep, smooth holes, even if you enter the wood at an angle. The lead screw forces a feed rate that works well in softwoods, letting contractors bore big holes through a stack of studs at once, for plumbing and electrical components. But that aggressive feed rate can be a problem in hardwoods, causing auger bits to jam in a drill press or cordless drill. Put them in a hand-powered brace, however, and they are a chairmaking champion, boring round mortises in square or round legs, at any angle.

Number drill bit gauge sizes range from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest). Although the ASME B94.11M twist drill standard, for example, lists sizes as small as size 97, sizes smaller than 80 are rarely encountered in practice.

Hole SawDrill Bit

A contractor’s favorite, spade bits offer the least expensive path to moderately large holes, and they work in handheld drills and drill presses alike. Although they’re designed to bore quickly through soft construction lumber, they drilled surprisingly clean holes in hardwoods in my tests. But the paddle-shaped design makes spade bits prone to vibration and rough cuts when they get dull, which they do relatively quickly. Also, while they can drill flat-bottomed holes, the long center tip leaves a deep, narrow hole on the middle. For all these reasons, buy spade bits in a pinch, but get a set of Forstners when you can afford them.

Hole SawDrill Bitfor Metal

Metric dimensioning is routinely used for drill bits of all types, although the details of BS 328 apply only to twist drill bits. For example, a set of Forstner bits may contain 10, 15, 20, 25 and 30 mm diameter cutters.

For many reasons, I consider a set of Forstner bits to be a must-have in any woodworking shop. Although there are slight differences in Forstner bits made by different manufacturers, the basic cutting geometry features a precisely machined rim, a center spur, and a chipper. These cutting elements work together to produce tearout-free, flat-bottomed holes in any type of wood. What’s more, Forstner bits can bore straight, angled, or overlapping holes. You can even bore a partial hole on the edge of a board, as shown in the photo at left. Count on these bits for perfect counterbores, smooth dog holes, decorative cutouts, and round recesses of all kinds—and for clearing the waste out of mortises without wandering.

The shortest standard-length drills (that is, lowest length-to-diameter ratio) are screw-machine-length drills (sometimes abbreviated S/M). They are named for their use in screw machines. Their shorter flute length and shorter overall length compared to a standard jobber bit results in a more rigid drill bit, reducing deflection and breakage. They are rarely available in retail hardware stores or home centers.

SpadeDrill Bit

Number and letter sizes are commonly used for twist drill bits rather than other drill forms, as the range encompasses the sizes for which twist drill bits are most often used.

Center drills are available with two different included angles; 60 degrees is the standard for drilling centre holes (for example for subsequent centre support in the lathe), but 90 degrees is also common and used when locating holes prior to drilling with twist drills. Center drills are made specifically for drilling lathe centers, but are often used as spotting drills because of their radial stiffness.

These five types of big bits look very different from each other, and perform differently as a result. This chart gives you their basic capabilities at a glance, but be sure to read the full write-ups that follow for all the important details. Price ranges are for individual bits.

Number and letter gauge drill bits are still in common use in the U.S. and to a lesser extent the UK, where they have largely been supplanted by metric sizes. Other countries that formerly used the number series have for the most part also abandoned these in favour of metric sizes.[citation needed]

The image shows a long-series drill compared to its diametric equivalents, all are 11⁄32 inch (8.7313 mm) in diameter. The equivalent Morse taper drill shown in the middle is of the usual length for a taper-shank drill. The lower drill bit is the jobber or parallel shank equivalent.

Metric drill bit sizes define the diameter of the bit in terms of standard metric lengths. Standards organizations define sets of sizes that are conventionally manufactured and stocked. For example, British Standard BS 328 defines 230 sizes from 0.2 mm to 25.0 mm.

Spotting drills are available in a relatively small range of sizes, both metric and imperial, as their purpose is to provide a precise spot for guiding a standard twist drill. Commonly available sizes are 1/8", 1/4", 3/8", 1/2", 5/8", 3/4", 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm and 18 mm. The drills are most ordinarily available with either 90° or 120° included angle points.

Below is a chart providing the decimal-fraction equivalents that are most relevant to fractional-inch drill bit sizes (that is, 0 to 1 by 64ths). (Decimal places for .25, .5, and .75 are shown to thousandths [.250, .500, .750], which is how machinists usually think about them ["two-fifty", "five hundred", "seven-fifty"]. Machinists generally truncate the decimals after thousandths; for example, a 27/64" drill bit may be referred to in shop-floor speech as a "four-twenty-one drill".)

Anatomical details vary greatly when you move from one big bit type to another. So it’s not surprising that there are differences in cost and performance. By considering the following factors, you can make sure that you get the results you’re after, and that you’re not using an expensive bit to do work that a more affordable bit can tackle effectively.