Drill Bits Buying Guide

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Drill Bits Buying Guide

For people who have not used drills much, there might be the expectation that there is only one type of drill bit and that drills can only be used for one thing. For most drilling applications, this assumption would be correct, but it also underestimates the many potential uses of a drill. Depending on the drill bit used, drills can be used to bore into a wide variety of materials and provide a number of other applications, such as chipping, chiseling, and deburring. Drill bits can be found at hardware and home improvement stores as well as mass-market department stores. If one were to look online, then eBay has the widest selection of drill bits available. The site also provides the opportunity to find an excellent bargain. In this buyer's guide, an overview of drill bits will be provided, including materials and styles of bit.


Drill Bit Materials

Drill bits are comprised of steel and harder materials. Please see the following table for an introduction into the various materials used in drill bits. The table goes from least to most durable material.
 

Material

Properties

Applications

Steel

Inexpensive, but dulls quickly when used in hardwood or harder materials

Excellent for boring into soft wood

High-speed steel (HSS)

Harder than steel; will stay sharp longer

General purpose

Black oxide

Nearly twice as durable as HSS bits

General purpose

Titanium-coated

More durable than steel and HSS (up to six times more durable than HSS), but more expensive; reduces friction on the drilling surface to allow for cooler drilling

General purpose

Carbide-tipped

Provides more durability than above materials

General purpose

Zirconium-coated

Smooth, hard finish provides reduced friction and improved durability

General purpose

Cobalt

Dissipates heat quickly; extremely hard

Used to bore into stainless steel and other metals


Generally, the harder and more durable a drill bit is, the more expensive it will be. Users must balance their drilling frequency with the price point to determine which drill bit is the most appropriate.


Drill Bit Types

Once a person determines how much the drill bits will be used and picks a material, then drill bits can be selected for various applications. Each reason to use a drill has a bit that will be most appropriate. The following sections have bits for general drilling as well as boring into various materials.

Universal Bits

For drillers that have a variety of uses for their drill, including general purpose drilling, universal bits can be selected. These bits will work equally well in wood, metal, plastic, and other materials.

Twist Drill Bits

The twist drill bit is the most common type of bit. The bit has a cutting point at the tip with helical flutes surrounding a cylindrical shaft. The flutes move the material being drilled away from the hole. Most twist drill bits have a point angle of 118 degrees, but this angle can be optimized for the material being drilled into. A 90-degree angle can be used for materials such as plastics, and a more obtuse angle of approximately 150 degrees can be used for harder materials.

Step Drill Bits

Step drill bits can be used in materials such as aluminum or plastic because the characteristics of the flute prevent clogging. The bit has a tip ground to a different diameter. If the transition from the ground and original diameter is straight, the bit forms a counterbore. If the transition is angled, the bit forms a countersink.

Unibit

With a stair-step profile, a unibit can be used to bore a variety of hole sizes. Usually used for sheet metal and electrical, the conical bit can drill a range of holes to speed up installation of fixtures. Unibits can also be used to deburr holes created by other bits.

Metal Drill Bits

While universal bits are good for general purpose drilling, they will not work repeatedly for metalworking projects. Metal drill bits are harder than universal bits and often are made with a specific purpose in mind.

Center and Spotting Drill Bits

Used in metalworking, center and spotting drill bits provide an initial hole or an indentation so that a larger drill can bore a larger hole. These drill bits can be used to keep traditional drill bits from wandering when drilling a previously unprepared surface. Spotting drill bits should not be used with carbide-tipped bits, which are designed to start a hole on their own.

Core Drill Bits

Core drill bits can either be used to enlarge holes or extract a core from a material. Although the bits have the same name, they have different designs. The hole enlarger bits do not have a point and have three or four flutes to ensure an even cut. This bit also enhances the finish of the hole. The core extracting bit is hollow and cylindrical. These bits are sometimes used in geological work.

Left-Hand Bit

Left - hand bits are used in functions in which repeated holes are required. The bits allow the continuation of a machining operation where the spindle can not be reversed. Screw extractors are a type of left-hand bit that allow a user to remove damaged screws.

Wood Drill Bits

Because wood is softer than metal, drill bits designed for use with wood can be made from softer materials. They also have differently designed flutes and tips to better bore into wood.

Lip and Spur Drill Bits

Lip drill bits have a tip with a sharp spur and four sharp corners to bore into wood. The spur pushes into the soft wood and keeps the bit aligned. These drill bits are also effective in softer materials such as plastic. For metal, only the thinnest sheet metal can be used with a spur drill bit. These bits range in diameter from 0.125 to 0.625 inches.

Wood Spade Bits

Wood spade bits have a pointed and flat bit that can be used for rough boring into wood. The point is surrounded by two cutters, which have spurs to provide a cleaner hole. These bits are intended for high-speed use and they often cause splintering when they are removed from the workpiece. Spade bit sizes range from 0.25 to 1.5 inches.

Spoon Bits

Spoon bits have a grooved shank with a bowl-like shaped point. The spoon part of the bit starts the hole. Spoon bits are often used by chair makers to create holes in the seats and arms of chairs. The spoon bit is inserted into the hole and rotated clockwise with a carpenter's brace until the appropriate taper is created. The spoon can be honed via a slipstone on the inside of the cutting edge.

Forstner Bits

Forstner bits can be used to bore flat-bottom holes with precision without respect to the grain of the wood. They can be used to cut overlapping holes or they can cut the edge of a block of wood. Forstner bits require a great deal of force, so they are generally not used with hand tools. The bit has a center point and a cylindrical cutter that shears the wood fibers at the edge of the bore.

Auger Bits

Auger bits have a long spiral flute for removing chips effectively. There are two main types of auger bit: Jennings and Irwin. Jennings includes two spurs, two radial cutting edges, and a screw tip that is self-feeding. The Irwin design includes a vestigial flute on one of the cutting edges, which affords greater space for removing waste.

Masonry Drill Bits

Usually used with a hammer drill, masonry bits are generally made from soft steel. The cutting edges are comprised of an insert of tungsten carbide which is brazed to the steel core. The hammering breaks up the masonry at the tip of the drill and the dust is carried away by the rotating flutes. The bits are often shaped to allow the bit to slide when the chuck is hammering, but without the whole chuck exhibiting a hammering motion.

Glass Drill Bits

To drill into glass, a glass drill bit can be used that has a carbide point shaped like a spade. These bits are not durable because they generate high temperatures. Holes are drilled at low speed and made bigger by increasingly larger bits. Bits can also be drilled with diamonds, which tend to last longer than metal glass drill bits.

Installer Bits

Installer bits are used to thread a wire through a hole. The bits are used with hand-portable power tools and the bit drills a transverse hole through the bit near the tip. Installer bits can be designed with various materials for drilling into metal, masonry, and wood.


How to Find Drill Bits on eBay

eBay has all types of tools for home improvement and other projects. To find them using the category directory, you should start at the Home, Outdoors & Decor portal. From there, you can go to the Tools section, followed by the either Hand Tools or Power Tools. For electrically-powered drills, the power tools section is appropriate, and also contains a subcategory for Drill Bits. You can further narrow your search by specifying condition of the bit, either new, used, or refurbished (by manufacturer or seller).

Saving a Search in eBay

If you'd like to browse search results at a later time or would just like to get daily updates on the drill bits available, you can save a search. After you perform a search, there will be a save your search link near the top of the search results. By saving a search, you can access search results at any time from your My eBay page. Another option is have an email sent to you daily with results of your search. You can also perform this option via My eBay. In this way, no deal on a drill bit will get past you.


Conclusion

As this guide has shown, there is a little more to drill bits than just what size hole a person wants to create. There are drill bits designed for metals, woods, and other materials. This guide has provided a number of details on drill bits for metals, which can stand high temperatures, and for wood, which can easily remove sawdust from the drilling area. There are bits made for hand tools and others for large manufacturing applications. Additionally, there are drill bits made from a wide range of metals and diamonds that can be used to bore holes into almost anything. For whatever job a person wants to pursue, he or she should ensure that the drill bit is appropriate for the task. Drill bits for any task can be found on eBay. The site has a deep selection of drill bits and provides a robust amount of information on each one.

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