B Is for Bridgeport

Metalworking Glossary for the Letter B


See the index to the Glossaries here:

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  • Babbitt. A metal alloy of tin, antimony, lead, and copper with antifriction properties that making the ideal material for manufacturing bearing inserts.
  • Back Clearance Angle. In sawing, the back clearance angle is the angle of the back of a saw blade tooth.
  • Back Gauge. An adjustable stop on a metalworking machine used to accurately position a workpiece for cutting, bending, punching, or other functions. It is usually found at the opposite end of the worktable or machine from where the workpiece is being fed, hence the term “back.” On a CNC machine, the back gauge is usually automated and programmed through the control to reposition as needed throughout the operation.
  • Back Gauge Origin. On a press brake, the back gauge origin is a preset starting position of the back gauge in relation to the center of the V-die opening and used as a reference for all positioning of the back gauge during an operation.
  • Back Rake. The back rake is the angle of inclination of the face of a tool’s cutting edge and from the nose to the rear along a longitudinal axis. It can be positive, neutral, or negative. It protects the point of the cutting tool, affects chip thickness, and guides the direction of chip flow.
  • Backlash. The play (looseness) or lost motion between the faces of meshing gears or threads.
  • Band Speed. The rate at which a band saw blade moves across a workpiece, usually measured in surface distance per minute, such as surface feet per minute (s.f.m.).
  • Band Tension. In a band saw, the tension of the blade is its tautness, measured in pounds per square inch, at a certain point as the idler band wheel is forced away from the drive band wheel.
  • Band Wheels. In a band saw, they are the wheels around which the blade is tensioned and turns.
  • Bandsaw. A power-driven saw featuring a narrow, continuous blade with teeth on one edge that can move at high speed around two pulley wheels.
  • Bar Stock. Bars of various lengths and diameter, used to create workpieces from. They are found in round, square, flat, hexagon, octagon, and other shapes.
  • Base. The foundation of a mill or other machine.
  • Beam Drilling Line. A drill line is a large, enclosed, CNC structural drilling system that can perform a wide range of operations needed in steel fabrication, such as drilling, milling, countersinking, notching, tapping, and scribing. They are usually equipped with automatic tool changers.
  • Beam Strength. A term in band sawing referring to the strength of the blade as measured by its deflection resistance. Beam strength is affected primarily by the thickness and width of the blade, the span, and the amount of blade tension present.
  • Bearing. A metal ball or other roller placed between moving parts to reduce friction and wear.
  • Bed Plate. Also known as a base plate, clamping plate, floor plate, or test bed, a bed plate is used as a ridged surface for assembly, inspection, layout, marking and testing.
  • Bed Type Milling Machine. A vertical mill without a knee or saddle that has its table mounted to a rigid bed. The spindle of a bed mill is attached to a pendant that can be raised or lowered in relation to the workpiece. The spindle can move in one axis (a simplex mill), two axes (a duplex mill), or three axes (a triplex mill). It is also known as a fixed-bed type mill.
  • Bed. The bed is the sturdy, horizontal base section of a machine like a lathe to which all other parts attach.
  • Bedways. Also known as just “ways,” the bedways on a lathe are the precision machined linear tracks on which the carriage and the tailstock travel.
  • Bend Angle. In metal fabrication, it is the angle that is created between the flange and the rest of the part when the bending operation is completed.
  • Bellows. A device commonly used to force air into a hearth to keep the flame going during forging.
  • Belt Grinder. Like belt sanders in design and operation, the more powerful belt grinders are designed remove a larger portion of material from a workpiece, not just minor imperfections.
  • Bench Grinder. A grinder that is designed to be mounted to the top of a workbench. Most have two different grinding wheels, a courser one for material removal and a finer one for finishing a workpiece. The grinding wheels can usually be interchanged with buffing wheels or wire brushes. Bench grinders are often used for sharpening cutting tools.
  • Bench Lathe. A bench lathe is a name for a fully functioning engine lathe that is small enough to be mounted on a bench.
  • Bend Test. A test used to determine the ductility of a piece of metal. The term bend test also applies to a procedure of flexing a bandsaw blade test the strength of the weld holding it together.
  • Bevel. Any surface that is not at right angles to another surface. A bevel can be cut or ground into the edge of a metal plate or other object (like a pipe) to remove a sharp corner for safety, to mate two plates or pipes at a right angle to each other, as a decorative measure for appearance, or to create a space in which welding metal can adhere when the part is being welded to another part.
  • Bevel Gears. Gears that are shaped like cones so that they can engage at right angles.
  • Bevel Protractor. A metal tool with a straight-edge arm that can pivot away from the main arm or base and measure an angle between two sides of a workpiece. Vernier scales are sometimes incorporated into a bevel protractor to allow more precise readings.
  • Billet. A semifinished length of metal that has a round or square cross-section and that was created through continuous casting or extrusion or by hot rolling an ingot or bloom.
  • Bit. An interchangeable cutting tool for a drill, mill or similar machine tool that is precision machined from hardened steel tool.
  • Blacksmith. Someone who uses heat, hammers, and specialized tools to forge iron, steel, or similar metals into objects. A smith in general is someone who crafts with metal—such as a tinsmith—while the term blacksmith specifically refers to the black color of heated iron.
  • Blade Width. The measurement of a band saw blade from the tip of the tooth to the back.
  • Blank. A blank is the raw metal workpiece that is cut, punched, or otherwise removed from the original metal stock. The blank can then be machined, fabricated, or forged as needed by the metalworker to create a part. The process of punching a blank from flat metal is called blanking. In forging, a blank is also called a slug, a multiple, or forging stock. “Blank weight” refers to the weight of a blank when it’s been sawed, deburred, and otherwise prepared and is ready for forging or another process.
  • Blast Furnace. A tower-shaped smelting furnace used to make iron by blasting hot, compressed air into the bottom.
  • Blind Hole. A hole made in a workpiece which doesn’t penetrate through to the other side.
  • Blocker-type Forging. An operation that uses an impression die to form the metal progressively into the approximate shape and contour of the final part, which will then usually be machined into its completed shape.
  • Bloom. In forging, a bloom is a semifinished piece of steel produced from an ingot. Blooms are like billets but are usually larger.
  • Bore Gauge. A bore gauge is used to accurately measure the inner diameter of holes in precision machined components.
  • Boring Head. In milling, a boring head holds a tool that is rotated off center into a previously bored hole to enlarge it. Used when a very accurate hole is needed, it can be adjusted very minutely to gradually increase the diameter of the cut.
  • Boring Mill. Not a traditional milling machine, a boring mill is primarily used to enlarge existing holes, usually involving very long workpieces. A jig borer is a type of vertical boring mill.
  • Boring. Boring means to make a hole. As a lathe function, boring enlarges an existing hole in a workpiece or creates a completely different shape.
  • Boss. In forging, the term “boss” refers to a usually cylindrical protrusion extending from the surface of the main body of a forged workpiece.
  • Bottom Bending. The press brake bending technique called bottoming or bottom bending uses the punch to push the metal down to the bottom of the die. This is different than other processes, such as coining (which also compresses the metal at the bottom of the die) or air bending (which only presses the metal down partway into the die).
  • Bottom Dead Center. The position of a press brake ram when it is fully closed into the die, a position that differs depending on the tooling. When the brake is opened to maximum height, it is referred to as top dead center.
  • Box Milling Machine. A bench-mounted, low-end mill used by hobbyists for simple milling processes. It gets its name because the head rides up and down on a box way.
  • Brake. Various machines from light gauge manual sheet metal folding machines (leaf brakes) to heavy, powered plate metal benders (press brakes) are known by the term “brake.” The word comes from the Middle English verb “breken,” meaning to break, but also conveying the idea of deviating from a straight line, such as swerving or deflecting. In the case of these machines, the term was applied to indicate a directional change in a flat piece of metal by bending it.
  • Brake Lathe. A brake lathe is a specialized lathe used in automotive shops to resurface brake discs and drums.
  • Brass. A nonferrous metal alloy composed mostly of copper and zinc.
  • Bridge Milling Machine. Another name for a gantry mill.
  • Bridgeport Milling Machine. A brand name, the term Bridgeport is often used in the industry to describe the style of vertical turret knee mill that has been replicated by other manufacturers since the Bridgeport company innovated the original in the 1930s.
  • Brine. In metalworking, brine is a saltwater solution that can be used for quenching or cooling steel or other metal during a heat-treating process.
  • Brinell Hardness. A measurement of the hardness of a metal tested by forcing into the material a hardened metal ball of a specific diameter under a specified load.
  • Broach. A long, tapered cutting tool with teeth for removing material from a workpiece when repeatedly passed over its surface or into an existing hole.
  • Bronze. A nonferrous alloy primarily consisting of copper with an amount of tin added (usually 12-12.5%). Other metals and non-metals may be present in the alloy, including aluminum, arsenic, manganese, nickel, phosphorus, silicon, and/or zinc.
  • Buff. To polish a surface to a smooth finish of high luster using a cloth or a fabric-covered wheel.
  • Bull Gear. The larger of two spur gears that are engaged in a machine (such as the bull gear of a shaper). The smaller spur gear is usually referred to as a pinion.
  • Bundle Cutting. Stacking and clamping multiple workpieces evenly to cut through at a single time on a bandsaw or other wide-bladed saw.
  • Burnishing. A process using a metal harder than the workpiece to create a smooth and glossy surface finish.
  • Burr. A sharp edge left over on a metal part after it is cut. Burrs are removed during a finishing process called deburring. The term burr also refers to a rotary cutting tool designed to be used in drilling.
  • Bushing. A sleeve or a lining for a moving part like a bearing or a drill jig to minimize wear.