| adjustable boring head |
A toolholder used in boring operations that require a hole diameter larger than that of the tool. An adjustable boring head can be set to bore differently sized hole diameters. |
| bore gage |
A hole inspection gage that makes three points of contact within the hole. Bore gages are handheld, variable instruments that provide very accurate readings of hole sizes. |
| boring |
The process of enlarging an existing hole with a single-point tool. Boring removes small amounts of material to achieve tight tolerances and finishes. |
| boring tool |
A long bar used to position a single-point tool for boring operations. Boring enlarges existing workpiece holes. |
| center drill |
A type of drill with a wide shank and a 60° angle tip. The center drill is used to start a hole to ensure that the hole is machined in the right location. |
| center hole |
A shallow hole used to locate other holemaking operations. Center holes are created with center drills. |
| chamfer |
A process that adds a small, angled surface on the end of a shaft, around the opening of a hole, or along an edge. Chamfering removes the sharp edge and helps remove burrs. |
| chamfer tool |
A tool that creates an angled surface which eliminates a sharp corner on a workpiece. Chamfer tools are available in a range of angles. |
| chips |
A piece of metal that is removed form a workpiece during cutting or grinding. Chips are tiny curls, shards, fragments, shavings, or particles of metal. |
| collet |
A split-sleeve device that expands or contracts to hold a cutting tool or workpiece in place as it rotates. Collets are designed to hold specific dimensions. |
| concentric |
Having a common center or sharing the same axis with another object. Concentric objects are generally circular or cylindrical. |
| conical |
Cone-shaped. Conical workpiece features gradually change from a larger diameter to a smaller diameter. |
| counterboring |
An operation that enlarges the end of a drilled hole to allow room for a head of a screw or nut. Counterboring produces an enlarged opening with a flat interior and square shoulder |
| counterboring |
An operation that enlarges the end of a drilled hole to allow room for a head of a screw or nut. Counterboring produces an enlarged opening with a flat interior and square shoulder. |
| countersinking |
An operation that cuts a conical surface into a hole. Countersinking allows the head of a screw with a matching conical angle to rest flush with the workpiece surface. |
| countersinking |
An operation that cuts a conical surface into a hole. Countersinking allows the head of a screw with a matching conical angle to rest flush with the workpiece surface. |
| crests |
The external ridge, or high point, of a thread. Crests of screw threads fit in the internal grooves, or low points, of a tapped hole. |
| cutting fluid |
A type of coolant used to cool or lubricate a metal cutting process. Cutting fluids are typically oil- or water-based liquids. |
| cutting speed |
The rate at which a single cutting edge of a cutting tool rotates in one minute. Cutting speed is measured in surface feet per minute (sfm) or meters per minute (m/min). |
| deflecting |
Unintentionally deviating from a straight line or plane when a force is applied. Deflecting in drilling can cause poor hole location and dimensions. |
| depth factor |
A set of constant fractions used to determine the proper depth for common countersink angles. The depth factor for the angle multiplied by the fastener head diameter determines the depth. |
| dowel pin |
A short, cylindrical rod. Dowel pins are fitted tightly into holes to prevent motion or slipping. |
| drill bushings |
A hardened steel tube used to guide holemaking cutting tools such as drills and reamers. Drill bushings are used when a counterbore tool does not have a pilot. |
| drill chuck |
A type of toolholder that tightens to grip holemaking tools on the mill. Drill chucks allow for quick installation and removal of various tools. |
| drill point |
The tip of a drill that contains the cutting edges. The drill point performs all cutting as the drill moves into the workpiece. |
| drilling |
The process of using a multi-point, or multi-edge, tool to penetrate the surface of a workpiece and make a round hole. Common drilling operations include center drilling and twist drilling. |
| edge finder |
A rod shaped tool used to find the exact edge of a part along the X and/or Y axis. Edge finders are commonly used in milling to locate part zero. |
| end milling |
A milling operation that uses a narrow mill to create slots, pockets, and contours in a workpiece. End milling may cut with both the bottom and sides of the cutting tool. |
| face milling |
A milling operation that produces a flat workpiece surface using a face mill cutter. Face milling is primarily used on the top workpiece surface. |
| flush |
Two or more level, adjacent surfaces. Flush surfaces form a flat plane. |
| flutes |
A straight or helical recessed feature on the periphery of a cutter. Flutes allow chips to flow away from the cut. |
| knee crank |
A handle used to raise and lower the knee and worktable on a milling machine. The knee crank features a micrometer dial that allows operators to adjust the feed rate incrementally. |
| length-to-diameter ratio |
L/D ratio. A numerical value comparing the length of a cylindrical tool or workpiece to its diameter. Higher length-to-diameter ratios offer less rigidity; 4 to 1 is typically the maximum ratio for standard cutting tool steels. |
| machinability |
The relative ease with which a machining process, such as milling or turning, can remove workpiece material. Machinability depends on the properties of the workpiece material. |
| major diameter |
The distance from crest to crest of an external thread or from root to root of an internal thread. Major diameter is also called thread diameter. |
| micrometer adjustment nut |
A nut located on a threaded rod that is used to determine spindle depth. Micrometer adjustment nuts are numbered in thousandths of an inch or hundredths of a millimeter. |
| mill |
A manual machine that uses various cutting tools to remove metal from the surface of a workpiece. Mills are also called milling machines. |
| milling machine |
A manual machine that uses various cutting tools to remove metal from the surface of a workpiece. Milling machines are also called mills. |
| minor diameter |
The distance from root to root of an external thread or from crest to crest of an internal thread. Minor diameter of a tap measures the farthest distance from root to root on opposite sides of the tool. |
| multi-point |
A cutting tool that has two or more cutting edges. In holemaking, multi-point tools may also be known as multi-edge tools. |
| pilot |
The end of the counterboring tool that helps guide the cutter straight into the hole. Pilots are smaller than the rest of the tool and concentric to the drilled hole. |
| pin gage |
A hardened, cylindrical gage used to inspect the size of a hole. Pin gages are available in standard diameters. |
| pitch |
On a thread, the distance between a point on an individual thread to the corresponding point on the next thread. Pitches range from coarse, with few teeth, to fine, with many teeth. |
| pitch diameter |
The measured distance between points in the grooves between threads. Pitch diameter is the theoretical point where the threads of a fastener and the threads of a hole meet. |
| reamer |
A multi-point, or multi-edge, cutting tool with straight cutting edges, used to enlarge or smooth holes that have been previously drilled. Reamers may have straight or helical flutes. |
| reaming |
The process of using a fluted, multi-point tool to produce to remove small amounts of material from the interior surface of a hole. Reaming achieves tight tolerances and refined surface finishes. |
| reference point |
The established location of a tool, workpiece, or machine component. A reference point provides a location to accurately measure and create part features in a milling operation. |
| rigidity |
The condition of a workpiece, machine, or machine setup characterized as still and immoveable. Rigid components are fixed securely in place. |
| roots |
The internal ridge, or low point, of a thread. Roots of screw threads fit against the external crests, or high points, of a tapped hole. |
| scale dial |
An analog device that measures linear movement. Scale dials are numbered collars attached to the feed handles and knee crank on manual mills. |
| shoulder |
A flat step or plane in between two surfaces. Shoulders within holes provide space for nuts and screws to sit below the top surface of a workpiece. |
| spindle depth |
The distance inside the workpiece that the spindle reaches during a cutting operation. Spindle depth on the manual mill is controlled by setting the micrometer adjustment nut or using the knee crank. |
| spindle speed |
The rate at which the machine spindle rotates. Spindle speed is typically measured in revolutions per minute. |
| surface finish |
The degree of smoothness of a part’s surface after it has been manufactured. Surface finish is the result of the surface roughness, waviness, and flaws remaining on the part. |
| tap |
A cylindrically shaped, threaded device that either cuts or presses threads into the interior of a pre-drilled hole. A tap’s external teeth match the internal threads it is designed to produce. |
| tap drill size |
The size of the drill required to create a specific threaded hole. Tap drill size determines the size of the hole before tapping. |
| tapping |
The process of cutting internal threads in a round hole with a multi-point tool. Tapping is performed only after first drilling a hole. |
| tapping fluid |
A substance used to cool and lubricate the cutting tool and workpiece in a tapping operation. Tapping fluid is typically oil-based. |
| telescope gage |
A measuring instrument with a spring-loaded device used to check the inner diameter of a part. Telescope gages are then measured with a micrometer to get the proper value. |
| thread diameter |
The distance from crest to crest of an external thread or from root to root of an internal thread. Thread diameter is also called major diameter. |
| thread gage |
A measuring instrument used to inspect the threads of a part. Thread gages are made for either internal or external thread inspection. |
| threads |
A long, spiraling groove that may appear on the interior or exterior of a workpiece surface. Threads help fasteners, such as screws, grip material and hold components together. |
| through hole |
A hole that passes through the entire thickness of a workpiece. Through holes pass through two workpiece surfaces and have no bottom. |
| tolerances |
A blueprint specification indicating an unwanted but acceptable deviation from a given dimension. Tolerances state the allowable difference between a part and its intended design. |
| twist drill |
A common drill characterized by helical flutes along its length and two cutting edges at the drill point. Twist drills commonly have an 118° or 135° tip. |
| walking |
Unintentionally moving off-center or away from the intended tool location. Walking is another term describing deflection. |