D Is for Drill Press

Metalworking Glossary for the Letter D

See the index to the Glossaries here:

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• D-bit Grinder. A type of tool bit grinder that gets its name as an abbreviation of the Deckel Company, a German machine tool producer that was the original manufacturer of that type of grinder. It was designed primarily to produce single-lip cutters for pantograph machines, a popular type of simple milling machine used for copying parts (later made obsolete by CNC mills).
• Daylight. Also called open height, daylight is the maximum open space a press brake can have with the ram fully extended.
• Debur. A process of removing burrs or sharp edges from a machined or fabricated metal workpiece. Various tools and machines can be used in deburring, including files, grinders, tumblers, and sandblasters.
• Decarburization. The loss of carbon from the surface of steel due to heat or chemical action. While it is usually present to a degree in forgings, excessive decarburization can result in a defective part.
• Deformation. Deformation in metalworking is the changing of the shape or size of an object through some process. As a lathe function, deformation is the removal of material to change the shape of a workpiece.
• Depth Gauge. Depth gauges are used to accurately measure the depth of a point from the surface of an object. Also called depth indicators.
• Depth Indicator. Also called a depth gauge, it is used to accurately measure the depth of a point from the surface of an object.
• Depth Micrometer. A precision device used to accurately measure the depth of a point from the surface of an object.
• Depth of Cut. How much material is being removed with each pass of a cutting tool. Adjusting depth of cut can affect surface finish, as well as change the life of a cutting tool.
• Depth of Penetration. In sawing, it is the distance the tooth tip penetrates the material during each cut.
• Descaling. A process of removing oxide scale from heated stock before or during a forging operation. Methods include scraping devices, wire brushes, a water spray, or the application of extra blows to the stock.
• Dial Gauge. Also called a dial indicator, a dial gauge is a widely used type of mechanical comparator. The two most common types are the plunger dial gauge and the level dial gauge. A plunger dial gauge is usually referred to as simply a “dial gauge” and measures the amount its plunger or spindle is pushed up inside its casing. A level dial gauge is often called a “test indicator” and measures the amount its lever or probe moves in a swinging arc.
• Dial Indicator. Another name for a dial gauge, a type of mechanical comparator.
• Diameter. The measurement through the center of a circle or sphere from outside edge to outside edge.
• Die. In metalworking, the term die refers to various types of tools used to cut or form metal to a specific shape. Types of dies include a stamping die, used with a press to cut and/or impress a workpiece; a die used with a matching punch to produce a hole of a particular size and shape in metal; a threading die that’s used to manually cut threads on a metal shaft; a press brake die that’s used in conjunction with a press brake punch to bend a sheet of metal to a certain angle; and a forging die used in a press to shape metal under high pressure and often with extreme heat. 
• Die Blocks. The metal forms or molds, usually used in pairs, that produce forgings. The forging impressions are machined into their interior surfaces.
• Die Grinder. A handheld high-speed tool that has a small grinding bit. Originally developed for creating contours of dies, die grinders have many applications where metal or other materials must be machined by hand. While they can be electric, they are usually powered by a shop’s compressed air line.
• Differential-pitched Milling Cutter. Another name for a variable-pitch cutter, it has unevenly spaced inserts for breaking up harmonic vibrations.
• Digital Readout. Abbreviated as DRO, a digital readout displays numbers to show the distance of movement during a metalworking operation on a machine.
• Disc Grinder. Another term for an angle grinder.
• Distance between Housings. An important specification of a press brake, the distance between the housings is the width between the sides of the machine’s frame. The tooling holders on most press brakes will extend a short distance past the sides of the machine, with a throat area cut into the side housings to accommodate the full-length bending of parts that have shorter flanges. Parts requiring a larger flange can be extended inside the frames of most press brakes, if their width doesn’t exceed the distance between housings.
• Distance of Cut. The distance a saw blade travels from where it enters a workpiece to where the cut is completed.
• Double Forging. A single forged workpiece designed to be cut apart and used as two separate pieces.
• Down Acting Press Brake. A press brake where the upper beam or ram moves the punch down into the die mounted on the lower beam.
• Draft. In forging, the term draft refers to a taper on the side of a forging that allows it to be removed from the dies.
• Draw-cut Shaper. A shaper named after the direction of its cutting stroke.
• Drawing Out. The process of making a workpiece longer in one dimension, while thinner in one or both other dimensions.
• Drill. A pointed tool that cut holes in a workpiece by being rotated. The term drill can refer to a piece of tooling (a drill bit), or to a machine that uses such a bit to create the hole (like a drill press or a hand drill).
• Drill Chuck. A drill chuck holds drill bits for use in a mill, but not tools like endmills.
• Drill Press. A drill press is a powered drill featuring a drill head attached on top of a column and an adjustable table that can be repositioned on the column depending on the size of the workpiece. While they often have tall columns mounted on a stand or to the floor, shorter versions called bench drills can be bolted to a workbench. Handles are turned on the drill head to move the spindle and chuck vertically in relation to the workpiece during the operation. They are popular due to their ease and accuracy.
• Drilling. A process of creating a hole through the application of a spinning drill bit to puncture a workpiece. As a lathe function, drilling is usually performed by mounting a drill bit in a drill chuck attachment in the tailstock of a lathe, allowing the workpiece rather than the drill bit to spin for the operation.
• DRO. Abbreviation for digital readout. A DRO is a display that shows numbers to measure the movement of an operation on a machine and keep track of accumulated distance.
• Drop Forging. A process used to shape metal by dropping a die mounted on a heavy hammer or ram onto a workpiece.
• Dross. Any unwanted byproduct of smelting ore. Also called slag or tailings.
• Drum Milling Machine. A mill that has a table called a drum that rotates a workpiece horizontally through three or four spindle heads (like the process with a rotary table mill).
• Ductility. The characteristic of a metal that measures what degree it can be stretched before it ruptures.
• Duplex Milling Machine. A mill that has a spindle that can move in two directions, both horizontally and vertically.