| alloys |
A uniform mixture of two or more materials. Alloys must have a metallic component as one of the materials in their composition. |
| aluminum |
A silver-white metal that is ductile, light, and thermally conductive. Aluminum is a soft metal that can tear when drilled, which reduces hole accuracy. |
| axial forces |
A force created parallel to the drill axis. Axial forces decrease as a point angle decreases. |
| axis |
An imaginary straight line passing through the center of an object. The axis is the line around which the drill rotates as it turns. |
| bearing surface |
The portion of the drill that makes contact with the sides of a hole. The bearing surface is along the margins on a twist drill. |
| bearing surfaces |
The portion of the drill that makes contact with the sides of a hole. The bearing surface is along the margins on a twist drill. |
| body |
The area of the drill that extends from the toolholder. The body is the component of the drill that enters the workpiece, and it is therefore subject to tool wear. |
| body diameter clearance |
The space between the margin and the rest of the land. The body diameter clearance provides space for cutting fluid to reach the workpiece and chip removal. |
| body diameter clearance |
The space between the margin and the rest of the land. The body diameter clearance provides space for cutting fluid to reach the workpiece and for chip removal. |
| boring |
The process of enlarging an existing hole with a single-point tool. Boring is most often performed on a lathe. |
| brass |
An alloy of copper and zinc. Brass has a tendency to grab a drill during drilling. |
| carbide |
A common cutting tool material used to make both indexable inserts and solid cutting tools. Carbide tools are very hard and wear resistant. |
| cast irons |
An alloy of iron, carbon, and silicon that contains at least 2.0% carbon. Cast iron is a hard, brittle material that creates short, discontinuous chips. |
| castings |
A metal part that is formed by pouring molten metal into a mold. Castings can be hard and brittle, which means they should be drilled with heavy-duty drills. |
| center drilling |
A drilling process in which a preliminary hole is made in a workpiece in order to guide the drill used to finish the hole. Center drilling can help prevent a drill from walking. |
| chatter |
Vibrations of the cutting tool that cause surface imperfections on the workpiece. Chatter reduces the quality of surface finish on a part and can be decreased by using more rigid tools and setups. |
| chipbreakers |
A feature or device designed to prevent chips from forming into long pieces. Chipbreakers can either be indentations on the surface of the drilling insert or a wafer clamped above the insert in the toolholder. |
| chips |
An unwanted piece of metal that is removed from a workpiece. Chips form when a tool cuts or grinds metal. |
| chisel edge |
The edge at the end of the web that connects the cutting lips. The chisel edge makes the initial penetration into the workpiece. |
| chisel edge angle |
The angle between the chisel edge and a cutting lip, as viewed from the end of the drill. The chisel edge angle influences feed rates and hole tolerance. |
| chisel edge angle |
The angle included between the chisel edge and a cutting lip, as viewed from the end of the drill. The chisel edge angle influences feed rates and hole tolerance. |
| chuck |
A clamping workholding device that grips the shank of a mounted drill. Chucks commonly have three or four jaws that adjust to the drill diameter. |
| clearance angle |
The slope of the side of a spade drill. The clearance angle provides space for the chips to exit the workpiece. |
| collet |
A slotted workholding device that grips the shank of a mounted drill. A collet is designed to hold a tool with specific dimensions. |
| concentric |
Two circular or cylindrical objects that share a common center or axis. Two objects that are concentric are aligned and on-center with one another. |
| conical |
Having a shape like a cone. The point of a typical twist drill is conical. |
| copper |
A reddish metal that is very ductile, thermally conductive, and corrosion resistant. Copper is a soft metal that creates long, stringy chips and should be drilled with drills that have high helix angles. |
| countersinking |
The cutting of a beveled edge at the end of the hole so that the head of a fastener can rest flush with the workpiece surface. Countersinking requires specially designed drill bits or points. |
| cutting edges |
The portion of the tool that performs the actual metal removal during a cutting operation. The cutting edges of a drill are located on the drill lips. |
| cutting fluid |
Any fluid used to cool or lubricate a metal cutting process such as drilling. A cutting fluid can be an oil- or water-based liquid, gas, or paste. |
| cutting forces |
The various stresses involved in a machining process. Cutting forces are determined by a combination of speed and feed rate, drill geometry, workpiece material, and other factors. |
| cycle times |
The time it takes to make a part or complete one step in the process of making a part. Drilling cycle times can be reduced by using modular drills, which have easily replaceable drill points. |
| deflection |
The unintended movement or deviation of a drill due to the application of mechanical force. Deflection of a drill can cause inaccurate hole location and dimensions. |
| dial indicator |
A device that measures the angles at the drill point to assure the drill point is symmetrical and on-center. A dial indicator is essential for ensuring that a drill has been properly reground. |
| diameter |
The distance from one edge of a circle to the opposite edge. The diameter of a drill helps determine the proper speed and feed at which operators should use the drill. |
| drill |
A tool used to penetrate the surface of a workpiece and make a round hole. A drill is a multi-point cutting tool. |
| drill geometry |
The angles and shapes formed by a drilling tool that indicate the jobs for which it is best suited. Drill geometry describes the drill's physical dimensions and attributes and cutting capabilities. |
| drill point |
The tip of a drill. The drill point contains the cutting edges, called the lips, of the drill. |
| drilling |
The process of using a multi-point tool to produce a hole in a workpiece. Drilling is often the first in a series of holemaking operations. |
| ductile |
Able to be stretched, drawn, or formed without fracturing. Ductile metals are easier to cut but are prone to tearing when drilled. |
| extended length |
The length that a drill extends from the toolholder. Extended length greatly influences the likelihood of drill deflection. |
| extrudes |
To shape metal through the use of force. The chisel edge of the drill extrudes the workpiece to begin shaping the hole. |
| fasteners |
A device that holds two or more objects together. Common fasteners include screws, bolts, and rivets. |
| fast-spiral drills |
A drill with a helix angle between 35 and 40 degrees. Fast-spiral drills, also called high-helix-angle drills, have excellent chip evacuation for drilling deep holes. |
| feed |
The rate at which the drill moves into the workpiece. Drilling feed is measured in either inches per minute (ipm), or millimeters per minute (mm/min), or inch per revolution (ipr), or millimeters per revolution (mm/rev). |
| feed |
The rate at which the drill moves into the workpiece. Drilling feed is measured in either inches per minute (ipm), or millimeters per minute (mm/min), or inches per revolution (ipr), or millimeters per revolution (mm/rev). |
| feed pressure |
The force applied to the drill to enable it to penetrate the workpiece. Feed pressure generally increases as the hardness of the workpiece increases. |
| fiber-reinforced plastics |
A composite material made of polymers strengthened through the addition of a web-like matrix of fibers. Fiber-reinforced plastics should be drilled with low-helix-angle drills because they have a tendency to grab the drill. |
| finishing |
A final metal cutting pass that emphasizes tight tolerances and smooth surface finish. Though finishing operations can be performed with a drill, usually they are done through procedures such as boring or reaming. |
| flex |
To bend due to the application of mechanical force. When drills flex, it can lead to issues, such as deflection, which lowers hole quality and reduces tool life. |
| flute |
A helical recess that wind up the length of a drill body. A flute enables the evacuation of chips from the cutting area during drilling. |
| flutes |
A helical recess that winds up the length of a drill body. Flutes enable the evacuation of chips from the cutting area during drilling. |
| forgings |
A workpiece formed by compressing metal between two dies to achieve a specific shape. Forgings are often hard and must be drilled with heavy-duty drills. |
| friction |
A force that resists the movement of two objects sliding against each other. Friction causes heat form in the areas where the objects make contact. |
| friction |
A force that resists the movement of two objects sliding against each other. Friction causes heat to form in the areas where the objects make contact. |
| general-purpose drill |
A drill with a standard web size, typically between 15 and 20% of the drill diameter. A general-purpose drill is often used on high-production drilling of cast iron, steel, and nonferrous metals. |
| grabbing |
The tendency of a metal to hold onto a drill during drilling. Grabbing can lead to poor surface finish and tolerance and can be reduced by using drills with low helix angles. |
| grinding |
The use of an abrasive to wear material away to achieve highly accurate measurements. Grinding can achieve tight tolerances and finishes. |
| grinding |
The use of an abrasive to wear material away to achieve highly accurate measurements. Grinding can achieve tight tolerances and high-quality finishes. |
| hard |
Resists penetration, indentation, and scratching. Hard metals generate greater cutting forces when drilled. |
| hardness |
A material's ability to resist indentation or scratching. Increasing hardness generally lowers the machinability of a metal. |
| heat |
The accumulation of an elevated temperature. Heat is often the result of friction and can cause tool degradation. |
| heavy-duty drill |
A drill with a larger web, typically between 20 and 40% of the drill diameter. Heavy-duty drills are used for drilling steel forgings, hard castings, and high-hardness ferrous alloys. |
| helical |
Having a spiral shape. Most drills have helical flutes. |
| helix angle |
The angle formed by the slope of the edge of a flute and a line parallel to the drill axis. Helix angles greatly affect the jobs for which a drill should be used. |
| helix angle |
The angle formed by the slope of the edge of a flute and a line parallel to the drill axis. The measurement of a helix angle greatly affects the jobs for which a drill should be used. |
| high-carbon steel |
A plain carbon steel that contains more than 0.45% carbon. High-carbon steels are extremely strong and hard, making them difficult to drill. |
| high-helix-angle drills |
A drill with a helix angle between 35 and 40 degrees. High-helix-angle drills, also called fast-spiral drills, have excellent chip evacuation for drilling deep holes. |
| high-production |
A machining operation that involves creating a large number of parts quickly. High-production drilling is often performed on steel, cast iron, and other common metals. |
| horsepower |
A unit of power used to describe machine strength. One horsepower equals 33,000 foot-pounds (ft-lbs) of work per minute or 746 watts. |
| inches per minute |
ipm. An English unit of measurement for feed that indicates how many linear inches a drill travels in one minute. Inches per minute corresponds to the metric measurement millimeters per minute (mm/min). |
| inches per revolution |
ipr. An English unit of measurement for feed that indicates how many linear inches a drill travels into the workpiece in one revolution. Inches per revolution corresponds to the metric measurement millimeters per revolution (mm/rev). |
| indexable |
A cutting tool with multiple edges that can be rotated into place. For indexable inserts, when one cutting edge wears out, an operator can turn the insert to expose a new cutting edge. |
| indexable insert drill |
A drill with cutting inserts clamped to a steel body. Indexable insert drills are among the most cost-effective drills because of their high metal removal rate. |
| inserts |
A removable, geometric cutting bit that has multiple cutting edges. Inserts are used with indexable insert drills. |
| ipm |
Inches per minute. An English unit of measurement for feed that indicates how many linear inches a drill travels in one minute. Drill feed can be measured in ipm, which corresponds to the metric measurement millimeters per minute (mm/min). |
| ipr |
Inches per revolution. An English unit of measurement for feed that indicates how many linear inches a drill travels into the workpiece in one revolution. Drill feed can be measured in ipr, which corresponds to the metric measurement millimeters per revolution (mm/rev). |
| L/D ratios |
Length-to-diameter ratio. A numerical value comparing the length of a cylindrical tool or workpiece with its diameter. Higher L/D ratios offer less rigidity. |
| land |
The area of a drill between flutes. The land is cut back slightly on both sides to leave room for chips to exit the cutting area. |
| left-hand twist drill |
A drill that rotates counterclockwise. A left-hand twist drill is mostly used to remove broken, right-hand threaded bolts. |
| left-hand twist drills |
A drill that rotates counterclockwise. A left-hand twist drill is mostly used to remove broken right-hand threaded bolts. |
| length-to-diameter ratio |
L/D ratio. A numerical value comparing the length of a cylindrical tool or workpiece with its diameter. Higher length-to-diameter ratios offer less rigidity. |
| lip face |
The flat surface on the side of the drill lip that is fed into the workpiece radially. The position of the lip face helps determine if a drill is right-handed or left-handed. |
| lip relief angle |
The measurement between a line tangent to the outer edge of the lip and a line perpendicular to the axis. The lip relief angle measures the clearance behind the cutting lip. |
| lips |
The cutting edges of a drill that extend from the chisel edge to the periphery. The lips perform the actual metal removal during drilling. |
| lips |
The cutting edges of a drill that extend from the chisel edge to the periphery. The lips preform the actual metal removal during drilling. |
| low-carbon steel |
A plain carbon steel that contains less than 0.30% carbon. Low-carbon steels are generally tough, ductile, and fairly easy to drill. |
| low-helix-angle drills |
A drill with a helix angle between 15 and 20 degrees. Low-helix-angle drills, also called slow-spiral drills, have high rigidity and can withstand greater cutting forces. |
| m/min |
Meters per minute. A metric measurement of speed that accounts for the number of linear meters that a point on the edge of a drill travels in one minute. Drill speed is measured in m/min, which corresponds to the English measurement surface feet per minute (sfm). |
| machinability |
The ability of a metal to be cut and shaped by machining processes such as drilling, milling, or turning. Machinability describes the ease or difficulty inherent in cutting a specific material. |
| margin |
A portion of the land that is not cut away. Margins guide the drill in the hole and maintain the drill diameter. |
| margin |
A portion of the land that is not cut away. Margins guide the drill into the hole and maintain the drill diameter. |
| metal removal rate |
MRR. The volume of metal removed in a given amount of time. Metal removal rate is measured in cubic inches per minute or cubic centimeters per minute. |
| meters per minute |
m/min. A metric measurement of speed that accounts for the number of linear meters that a point on the edge of a drill travels in one minute. Meters per minute corresponds to the English measurement surface feet per minute (sfm). |
| millimeters per minute |
mm/min. A metric unit of measurement for feed that indicates how many linear millimeters a drill travels in one minute. Millimeters per minute corresponds to the English measurement inches per minute (ipm). |
| millimeters per revolution |
mm/rev. A metric unit of measurement for feed that indicates how many linear millimeters a drill travels into the workpiece in one revolution. Millimeters per revolution corresponds to the English measurement inches per revolution (ipr). |
| mm/min |
Millimeters per minute. A metric unit of measurement for feed that indicates how many linear millimeters a drill travels in one minute. Drill feed can be measured in mm/min, which corresponds to the English measurement inches per minute (ipm). |
| mm/rev |
Millimeters per revolution. A metric unit of measurement for feed that indicates how many linear millimeters a drill travels into the workpiece in one revolution. Drill feed can be measured in mm/rev, which corresponds to the English measurement inches per revolution (ipr). |
| modular drill |
A drill consisting of an interchangeable and disposable point mechanically attached to a drill body. Modular drills can greatly increase production efficiency but tend to be less rigid than solid tools. |
| nickel alloys |
A metal containing a significant percentage of nickel. Nickel alloys are hard and should be drilled with low-helix-angle drills. |
| nonferrous |
A material that does not contain a significant amount of iron. Common nonferrous metals include aluminum and copper. |
| off-center |
When the components of a tool or part are improperly aligned with that tool or part's axis. When a drill flexes, it is forced off-center and will not create a hole in the desired location or of the desired dimensions. |
| on-center |
When the components of a tool or part are properly aligned with that tool or part's axis. A reground drill must be on-center or it will not perform correctly. |
| operators |
A person trained to run a specific machine. Operators are responsible for helping ensure that a machining process runs properly, efficiently, and safely. |
| perpendicular |
Two lines or objects that meet at a right (90°) angle. The lip relief angle is determined by measuring the angle between a line tangent to the outer edge of the lip and a line perpendicular to the axis of the drill. |
| plastics |
A lightweight, corrosion resistant material composed of larger polymer molecules. Plastics create long, stringy chips and should be drilled with drills that have high helix angles. |
| point |
The conical tip of a drill body that contains the cutting edges. The drill point is the only part of the drill that actually cuts metal. |
| point angle |
The angle formed by the cutting edges, or lips, of the drill. The point angle greatly affects how a drill cuts, with larger angles better suited for harder materials and smaller angles better suited for softer materials. |
| proportional |
A constant ratio or relationship between two or more values. The likelihood of drill deflection is proportional to extended length relative to its diameter. |
| radial forces |
A force created perpendicular to the drill axis. Radial forces increase as the point angle decreases. |
| reaming |
The use of a multi-point cutting tool to smooth or enlarge a previously drilled hole. Reaming is often a finishing process. |
| regrinding |
The process by which a tool is resharpened with an abrasive after extensive use. Regrinding, also known as sharpening, can help a tool perform optimally again, but it also reduces tool life. |
| removable drill tip |
The interchangeable portion of the drill that performs the actual cutting. The removable drill tip determines the drill geometry. |
| revolutions per minute |
rpm. A unit of measurement that indicates the number of revolutions a drill makes in the spindle in one minute. Revolutions per minute is an important factor in determining drill speed. |
| right-hand twist drills |
A drill that rotates clockwise. Right-hand twist drills are by far the most common drills. |
| right-hand twist drills |
A drill that rotates clockwise. Right-handed twist drills are by far the most common drills. |
| rigid |
Stiff and inflexible. Rigid drills are often required when drilling harder materials. |
| rigidity |
The quality of a workpiece, drill, machine, or machine setup characterized by being stiff and inflexible. A drill with good rigidity is often required for drilling harder materials. |
| rigidity |
The quality of a workpiece, machine, or machine setup characterized by being stiff and inflexible. A drill with good rigidity is often required for drilling harder materials. |
| rpm |
Revolutions per minute. A unit of measurement that indicates the number of revolutions a drill makes in the spindle in one minute. Drill speed is calculated in part using rpm. |
| screws |
A threaded device used for fastening parts or transferring motion. Broken screws can be removed using a left-handed twist drill. |
| service life |
The length of time a drill is expected to be operational before it must be replaced. Service life can be extended through selection of proper drill tool geometry. |
| setup |
The arrangement of tooling and fixturing on a manufacturing machine. A drilling setup with low rigidity may require a more rigid tool. |
| sfm |
Surface feet per minute. An English measurement of speed that accounts for the number of linear feet that a point on the edge of a drill travels in one minute. Drill speed is measured in sfm, which corresponds to the metric measurement meters per minute (m/min). |
| shank |
The portion of a drill that allows the drill to be held and driven. The shank is on the opposite end of the drill from the point. |
| sharpening |
The process by which a tool is resharpened with an abrasive after extensive use. Sharpening, also known as regrinding, can bring a tool back to optimal performance, though tool life will be reduced. |
| slow-spiral drills |
A drill with a helix angle between 15 and 20 degrees. Slow-spiral drills, also called low-helix-angle drills, have high rigidity and can withstand greater cutting forces. |
| soft |
Deforming easily when subjected to stress. Soft metals include aluminum and copper. |
| spade drill |
A drill with a wide blade at the tip capable of drilling very large holes. A spade drill's blade width often exceeds the diameter of the drill body. |
| speed |
The rate at which the drill rotates in relation to the workpiece. Drilling speed is usually expressed in surface feet per minute (sfm) or meters per minute (m/min). |
| spindle |
The part of the machine tool that rotates. In drilling applications, the spindle holds the drill. |
| stability |
The ability to remain firmly in position. Drilling machines with good stability create more accurate holes. |
| steels |
An alloy of iron and carbon containing less than 2.0% carbon. Steels often contain other elements to enhance various aspects of the metal. |
| strength |
A metal's ability to resist outside forces attempting to break or deform the metal. Increasing strength makes a metal more difficult to drill. |
| surface feet per minute |
sfm. An English measurement of speed that accounts for the number of linear feet that a point on the edge of a drill travels in one minute. Surface feet per minute corresponds to the metric measurement meters per minute (m/min). |
| tang |
The optional flattened end on some drill shanks that locks into the machine head and allows the drill to be rotated and driven securely. A tang allows a drill to be mounted on a lathe. |
| tang |
The optional flattened end on some drill shanks that locks into the machine workhead and allows the drill to be rotated and driven securely. A tang allows a drill to be mounted on a lathe. |
| tangent |
A line, line segment, or ray that touches a circle or object at exactly one point. The lip relief angle is determined by measuring the angle between a line tangent to the outer edge of the lip and a line perpendicular to the axis of the drill. |
| taper shank drill |
A drill with a tang or tapered shank. Taper shank drills are used when the drill must be mounted on a lathe. |
| taper shank drills |
A drill with a tang or tapered shank. Taper shank drills are used when the drill must be mounted on a lathe. |
| thrust |
The amount of force or drive exerted on a drill while it turns. Thrust occurs when the drill is accelerated in a linear direction. |
| titanium |
A silver-gray, strong, lightweight metal known for its corrosion resistance and strength-to-weight ratio. Titanium tends to work harden and should be drilled using drills with high helix angles. |
| tolerance |
An unwanted but acceptable deviation from a given dimension defined by a blueprint. Tolerance is improved through the correct selection of a chisel edge angle when drilling. |
| toolholder |
A device used to hold a cutting tool in place during machining. A toolholder can be a range of devices, including a milling cutter and a spindle. |
| toolholder |
A device used to hold a cutting tool in place during machining. A toolholder may also move the cutting tool into the workpiece, as in drilling. |
| torque |
The amount of force exerted to rotate a drill and cut a hole in a workpiece. More rigid drills can be subjected to greater levels of torque. |
| torsion strength |
The ability of a rotating drill to withstand the forces of workpiece resistance. Torsion strength is particularly important when drilling hard metals such as high-carbon steel. |
| twist drills |
A drill characterized by helical flutes along its length and a cutting point at the tip. Twist drills are the most commonly used type of drill. |
| walk |
To deviate from an intended path. The tendency of a drill to walk can be eliminated by center drilling prior to the drilling operation. |
| wear |
The erosion of material as a result of friction. Wear is common in tools that operate at excessively high speeds. |
| wear lands |
A worn portion of the drill near the cutting edges. Wear lands appear gradually due to abrasion and other cutting forces. |
| web |
The central portion of the drill body that joins the lands. The web forms the chisel edge at the cutting point on a drill. |
| web |
The central portion of the drill body that joins the lands. The web forms the chisel edge at the cutting point on a two-flute drill. |
| web thinning |
The grinding of the web and chisel edge to shrink them and return a drill to its original specifications. Web thinning greatly improves the performance of a reground drill. |
| work harden |
To increase in hardness due to plastic deformation during a cold working or machining process. Work hardening materials should be drilled using a bit with high helix angles. |
| workhead |
The component of a drilling machine that houses the spindle. The workhead holds and rotates the drill. |
| workpiece |
A part that is subjected to one or more manufacturing procedures, such as machining, welding, or casting, Workpiece material is a key consideration when determining proper drill geometry. |