With its unique functions and wide applicability, twist drill bits have become an indispensable and important tool in modern industrial manufacturing and play a key role. Understanding the material composition, application range, advantages and disadvantages of twist drill bits is crucial for the correct selection and efficient use of this tool. This article will explore various aspects of twist drill bits in depth to help you better understand.
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A twist drill bit is a cutting tool used to drill holes in a variety of materials, including wood, metal, and plastic. It consists of a cylindrical shank, a spiral groove that runs the length of the drill bit, and a pointed tip with two cutting edges. As the drill bit rotates, the spiral grooves effectively discharge the material being drilled, while the cutting edges precisely cut into the material. The angle and shape of the cutting edges vary depending on the type of material being drilled and the size of the hole required.
Twist drill bits come in a wide range of sizes, from tiny sizes of less than 1 mm in diameter to larger sizes of several centimeters in diameter, to meet a variety of different drilling needs. It can be used with a handheld drill for convenient and flexible operation, or mounted on a drill press for more precise drilling results.
High-speed steel is the most common material for manufacturing twist drill bits. HSS drill bits are made of a combination of steel, tungsten and other metals, and have excellent durability and can withstand high temperatures. They perform stably in drilling operations on a variety of materials.
Cobalt steel drill bits are similar to high-speed steel drill bits, but have a higher cobalt content. This makes cobalt steel twist drill bits more heat-resistant and durable, especially suitable for drilling operations in high-temperature environments.
Carbide twist drill bits are made of a combination of tungsten carbide and cobalt, and have extremely high hardness. They can easily drill through hard materials such as stainless steel and cast iron, making them an ideal choice for machining hard materials.
Diamond twist drill bits are mainly used to drill through extremely hard materials such as glass, ceramics, and stone. Diamond particles are embedded in the metal matrix, making them not only durable but also able to withstand high temperatures.
Titanium-coated twist drill bits are made of high-speed steel or cobalt steel, and are covered with a thin layer of titanium nitride coating on the surface. This coating greatly increases the wear resistance of the drill bit while helping to reduce friction when drilling.
It can be used to drill holes on a variety of different materials such as wood, metal, plastic, etc., and has a wide range of applications.
It is very simple to use and can be operated with a handheld drill or installed on a drill press, providing users with a convenient operation method.
It is widely available in hardware stores, home improvement stores and online retailers, making it convenient for users to purchase.
The price is relatively cheap, which is an economical choice for DIY enthusiasts and professionals.
With a variety of different sizes, users can easily find the drill bit size that suits their work needs.
Only round holes can be drilled, which may not meet the needs in some specific application scenarios.
When drilling certain materials, such as ceramics or glass, improper use may cause the material to break or crack.
When used for hard materials or improperly used, twist drill bits will quickly become blunt, affecting the quality of the hole and may damage the drill bit.
As the use time increases, the twist drill bit may need to be sharpened frequently to maintain its good drilling performance.
When drilling certain materials, such as metal, the twist drill bit will generate heat, which may cause the material to bend or the drill bit to be damaged.
Twist drill bits are commonly used to drill holes in wood and play an important role in furniture making, woodworking and DIY projects.
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Suitable for drilling holes in various metal materials such as steel, aluminum, copper, etc., and is a powerful tool in themetalworking process.
Can also be used to drill holes in plastic materials such as acrylic, polyvinyl chloride, polycarbonate, etc.
Can be used to drill holes in the wall for installing shelves, curtains and other household items.
Used with a hammer drill, it can drill holes in concrete or masonry to install anchors or bolts.
Woodcarvers often use twist drill bits to make decorative holes or create textures in wood carvings.
Used for drilling holes for bolts, screws and other fasteners.
In jewelry making, it is used to drill holes in beads, stones and other materials.
In model making, it can be used to drill holes in various materials such as plastic, wood or metal.
Twist drill bits are a type of cutting tool with multiple material options, a wide range of uses, and unique advantages and disadvantages. In practical applications, users need to select the appropriate twist drill bit based on specific drilling needs.
Twist drills (also commonly referred to as twist bits) are the most widely used of all drill bit types; they will cut anything from wood and plastic to steel and concrete. They are most frequently used for metal cutting, so they are generally made from M2 high-speed steel. At diameters up to about 1/2", twist drills are not only the cheapest of all bits a woodworker could use, they offer the widest selection of sizes. Although they are designed for cutting metal, they will work quite well in wood, if sharp. This generally means that they have not been used to cut hard materials such as steel.
A twist drill is a metal rod of a specific diameter that has two, three or four spiral flutes running most of its length. Two-flute drills are for primary drilling, whereas three- and four-flute drills are only for enlarging cast or punched holes in a production situation. The section between the two flutes is called the web, and a point is formed by relief grinding the web to an angle of 59° from the drill's axis, which is 118° inclusive. This forms a sloped cutting edge at the edge of the flute, which is called the lip. A twist drill is very inefficient at the point because the web leaves scant exit space for debris (called swarf) and because the point has a low surface speed compared to the periphery. For this reason, a good scheme for drilling larger holes is to first drill 1/4" or less and then follow with the drill of the desired diameter.
In addition to creating the cutting lips, the flutes provide a place for the swarf to be drawn out of the hole. The spiral expedites this, but the flute becoming impacted with swarf is always a niggling problem. For this reason, a twist drill must be constantly cleared; that is, completely withdrawn from the hole. If you do this frequently, the swarf will be flung away, but if you wait too long, you will have to stop the drill and manually clean the flutes. Clearing is much easier with a drill press than with a drill motor. Wood is a poster child for quickly impacting a twist drill, so even more frequent clearing than with metal is necessary. This problem can be somewhat ameliorated by now and then applying wax or spraying silicone to the drill.
Fractional size twist drill assortments are commonly offered in sizes between 1/16" and 1/2" in 1/64th inch increments. Number drills cover sizes between the fractional diameters below 1/4". Numbered between 1 and 80, they cover sizes from .228" (#1) down to ." (#80). Letter drills cover sizes between the fractional diameters from 1/4" to 1/2". An A drill is .234" and a Z drill is .413" diameter. This is somewhat confusing because the number series becomes smaller from 1/4" as the numbers increase and letter series get larger from 1/4" as the letters increase. Twist drills are also offered in metric sizing, so just about any diameter desired can be obtained.
Normal length drills, such as come in the average assortment, are called jobber length. If a longer drill is needed, a good hardware shop will offer an aircraft or extra-length drill. If a shorter twist drill is desired, it is referred to as a screw-machine drill. Twist drills are offered in solid carbide and carbide-tipped as well. Carbide-tipped is the choice for drilling concrete.
Twist drills are difficult for users to sharpen. Great lengths are taken during manufacturing to have the lips at the same vertical height and angle. If the resulting point is not perfectly centered, and each lip does not cut a chip of equal width and thickness, the drill will wander and you will end up with an oversize hole that may not be straight either. While a skilled machinist can sharpen a twist drill by eye on a bench grinder, it will only do non-critical work thereafter! Only a drill sharpening jig or a dedicated machine will restore, new out of the box, accuracy to a dull drill.
The attack angle of a twist drill is controlled by the rate of twist of the flute. Drills are generally manufactured for cutting steel, which happily works out well for wood as well. This is far too aggressive for nonferrous metals such as brass and copper, which like a 5° negative rake angle. Breakout as the drill exits the material on the far side is particularly troublesome and commonly results in the workpiece spinning on the drill press table or the drill motor spinning in the operator's hands. Either can result in severe injury. This dangerous situation can be almost completely overcome by creating a small flat on the lip that is parallel to the axis of the drill. Called lipping, it turns a unpredictable beast into a gentle pussy cat. What you are doing is effectively changing the rake angle of the drill to 0° instead of 15° positive. The flat does not have to be big, (1/64" or less). The downside of lipping is that the drill will no longer drill steel unless you sharpen the point sufficiently to remove the flat. If you only own one set of drills, that is good reason to keep the lipping flat no larger than necessary.
Plenty of speed is the order of the day when drilling wood. You can use up to RPM for drills 1/4" and smaller. Speed charts are readily available and it is good to have one on the shop wall. Center punching is a must if you want accurate hole location.
Twist drills are perfect when you want a very accurate diameter hole. Say you want a press fit for a 3/16" (." dia.) steel pin in a cabinet you are building. A #13 drill makes a .185 dia. hole, giving you a . press fit for the pin. When desiring a very accurate hole it is best to drill 1/64" undersize, and then make the final drilling with a new, or freshly sharpened, drill of the desired diameter. If drilling a large hole this could entail three drillings: drilling 1/4" to expedite the quick sinking of the larger hole you desire, drilling 1/64" undersize and final drilling of the desired size.
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