Metalworking Glossary "T"

T Is for Threading

Metalworking Glossary for the Letter T

See the index to the Glossaries here:

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• T-bolt. A square-headed bolt that is designed to be inserted into a worktable’s T-slots to secure a workpiece.
• T-slot. A slot milled into in the table of a machine tools for the purpose of securing a workpiece. T-slot nuts or square-headed T-bolts slide down the T-slots on a worktable and are tightened into specific positions to clamp the workpiece securely in place for a subsequent operation.
• T-slot Nut. A bolt designed to fit a T-slot track for workholding a part. It is used in conjunction with a bolt and a threaded clamp to secure the workpiece in position for machining or another operation.
• Table. The rectangular part of a machine that secures the workpiece. On a milling machine, the table sits on top of the saddle and parts are fixed to it using a vise, chuck or clamps. A mill table is moved under a milling cutter using X- and Y-axis handwheels.
• Tack Welds. Small, temporary welds scattered across workpieces, usually in lieu of fixturing, that hold parts together at the correct alignment for the final welding.
• Tailings. Any unwanted byproduct of smelting ore. Also called dross or slag.
• Tailstock. The tailstock of a lathe is at the opposite end of the bed from the headstock and can be used to support the workpiece or perform different functions. Its spindle does not rotate and includes a taper to hold various pieces of tooling. The tailstock can be repositioned along the bed and clamped in place to accommodate the workpiece.
• Tandem Press Brakes. Two press brakes that are set up next to each other with nothing between their tooling sets and that are controlled by the same controller to work together are referred to as tandem press brakes. Tandem brakes are an alternative to an extremely large press brake when very long parts need to be bent at a standard tonnage. The term tandem can be used to refer to more than two brakes, though some manufacturers will refer to three brakes as a trio and four as a quad configuration.
• Tang. A section on a piece of tooling to connect it to a handle or machine. The term can refer to either a whole shank (as in a press brake die) or just a flat part of a shank (as in a cutting tool) that fits into slot in the machine or a spindle to keep the tool from slipping.
• Tap. A tool bit used to cut threads on the inside of a previously drilled hole.
• Tape Measure. A basic metrology tool in metalworking, a measuring tape is used for determining long distances or diameters of round objects. Metrology standards set by NIST (the National Institute of Standards and Technology) state that a 6' long tape measure used for commercial purposes must be accurate to within 1/32".
• Taper. In metalworking, a machine taper is a device for fastening a cutting tool or a toolholder on the spindle of a machine.
• Tapering. To gradually reduce the width, thickness, or diameter along the length of an object. As a lathe function, tapering or “taper turning” produces a diagonal transition between two surfaces with different diameters, such as creating a cone.
• Tapping. Cuts threads into an existing hole, such as creating a thread on a nut.
• Teeth. Multiple pointed cutting edges along or around a fast-moving tool used to remove material from a workpiece, such as a bandsaw blade, a circular saw blade, or a broach. On an end mill, teeth are on the outside surface and are separated from each other by flutes (they are technically considered part of each flute).
• Tempering. The process of hardening metal by heating and then quenching it.
• Tensile Strength. The maximum stress that a metal or other material can withstand while being stretched or pulled before it breaks or shows strain.
• Tenth. Short for “ten-thousandth,” it is 0.0001" (one ten-thousandth of an inch).
• Test Indicator. Another name for a level dial gauge, it is a device that measures the amount its lever or probe moves in a swinging arc.
• Thou. Short for “thousandth,” it is 0.001" (a thousandth of an inch).
• Thread Gauge. A device used to measure the threads on a machined part.
• Thread Grinder. A CNC machine that cuts the threads of a screw with an abrasive grinding wheel.
• Thread Measuring Tools. Devices for measuring threads cut into a shaft include thread micrometers and thread pitch gauges.
• Thread Pitch. The distance from a point on one screw thread to a corresponding point on the next thread.
• Threading. Threading is a lathe function where a tool moves along the side of the spinning workpiece to cut a uniform helical groove or thread of a specific length and pitch in the part.
• Three-Axis Milling Machine. A mill that can perform an operation on a workpiece in three directions, milling in the X, Y, and Z axes.
• 3D Scanner. Optically based 3D scanners can be moved around an item to collect digital data that can be rendered on a computer to display a moveable model of the item that shows accurate dimensions from every side.
• 3-in-1 Machine. Another name for a combination lathe, a lathe used mostly by hobbyists that is combined with a mill, a drill press, or both in a single machine tool.
• Three-Roll Rolling Machine. Commonly called just a “3-roll,” it is a sheet metal or plate metal roll that utilizes three solid rolls to shape flat material that is rolled between them. Types of 3-roll machines include: a true pyramid roll, a now outdated machine with a moveable top roll centered over two rigid bottom rolls; an initial pinch 3-roll, with two front rolls that “pinch” the workpiece and feed it towards a moveable back roll; a double pinch 3-roll, a pyramid-type roll with a rigid top roll and two moveable bottom rolls that can pinch the workpiece between either of them and the top roll; and a variable geometry three roll, a pyramid-type roll with bottom rolls that can move out horizontally away from the top roll to accommodate different thicknesses of metal.
• Throat. Sometimes called throat depth, it is the distance a workpiece can be inserted into a metalworking machine before being impeded by a rear part of the machine frame. In the case of a press brake, it is the depth of the cutaway sections in the side housings that allow the tooling holders on the ram and bed to extend out beyond the width of the frame. While narrower workpieces can be inserted further into the brake, the amount of flange that can be bent at full length is limited by the throat depth of the housings. The hand tool known as a throatless shear doesn’t have a throat or guide down which a workpiece must be fed but allows the metal to freely move in relation to the cutting blade.
• Tolerance. The allowable deviation of distance, usually noted as “+/-” a certain number of thousandths of an inch, that a finished part can differ from the specified dimensions.
• Tommy Bar. Often shortened to “T-bar” and sometimes called a “spindle bar,” a Tommy bar is a cylindrical steel bar used as a lever to tighten and loosen some types of chucks and tool holders on a machine tool.
• Tongs. A tool used by a blacksmith for holding hot metals securely. The term can refer to other types of metal holders used to handle hot or cold forgings or other metal pieces. Forging billets and other stock often have a small portion of metal protruding on one end referred to as the “tong hold.”
• Tonnage. The term tonnage used in reference to metalworking equipment is a capacity measurement, especially in the case of machines like punches and press brakes that can perform differently sized jobs based on variable factors. These types of machines will usually include a tonnage chart to help operators determine what tonnage is required to complete a specific operation.
• Tonnage Control. The ability of a metalworking machine to vary the amount of tonnage it applies during an operation like bending.
• Tool and Cutter Grinder. Sometimes referred to as a T&C grinder, it is a grinder used for producing drills, endmills, step tools, and tool bits. It can also be used to sharpen such tooling and other cutting tools. It is usually a CNC machine with up to 5-axis control over multiple grinding wheels.
• Tool Steel. A hard, high-grade steel that is used to create tools and dies.
• Toolholding. A term used to describe process and apparatus for securing a tool in place for use on a machine tool.
• Toolpost. A part of a lathe carriage and holds the tool bit in place.
• Toolroom Lathe. A toolroom lathe is a high-quality lathe that has been optimized for heavy-duty work, such as in a toolroom. It is like an engine lathe, but is larger, more accurate, and runs smoother.
• Tooth Face. In sawing, it is the surface of a blade tooth on which chips form.
• Tooth Form. In sawing, it is the shape of a blade tooth, consisting of rake angle, spacing, and gullet capacity. It can be referred to as standard, skip, hook, variable, and variable positive.
• Tooth Life. In sawing, it is the useful life of a saw blade measured in the number of square inches of material that can be cut.
• Tooth Pitch. In sawing, it is the distance between the tips of teeth, measured in inches.
• Tooth Set. In sawing, it is the pattern in which teeth are offset from the saw blade, such as a raker set.
• Top Dead Center. The position of a press brake ram when it is opened to maximum height. The opposite position, when the ram is fully closed into the die, is referred to as bottom dead center.
• Top Slide. Another name for a compound rest on a lathe.
• Toughness. The ability of a metal to plastically deform before it fractures.
• Tracer Controlled Milling Machine. A mill that can replicate a part in a milled workpiece by tracing an original finished part.
• Tracking. In sawing, it refers to the alignment of a band saw blade on the band wheel.
• Translation Screw. Another name for a leadscrew on a lathe.
• Traveling Head Shaper. A shaper with a ram that has a crosswise “feed” movement in addition to the reciprocating cutting motion for use on large or heavy workpieces that can’t be mounted to the table of a normal shaper.
• Traverse. To move across the surface of a workpiece.
• Trepanning. A forging term the use of a hollow tool to remove a core of metal.
• Triplex Milling Machine. A mill with a spindle that can move in the X, Y, and Z axes.
• Trochoidal Milling. A type of face milling used for producing a slot in materials that are difficult to machine. It does so by using a smaller diameter cutting tool that follows a trochoidal cutting path to mill a slot wider than the tool itself.
• True Rake Angle. Also known as effective rake angle or resultant rake angle, true rake angle is a measurement showing the combination of the back rake angle and side rake angle of a cutting tool. True rake angle determines actual sharpness and has a significant influence in determining the amount of chip compression.
• Truing. Aligning a cutting tool (or a workpiece) so that a machining operation can be accurately done.
• Tube Flaring. A process of forming the end of a tube into a funnel shape so it can be held by a threaded fitting.
• Tumbler Gears. A pair of small lever-mounted gears used a lathe used to engage the leadscrew or change its direction.
• Turning. Turning is perhaps the most common lathe function, the removal of material from the outer diameter of a rotating workpiece by holding a cutting tool against it.
• Turret Drill. The head of a turret drill holds several different tools that can be rotated into place to be used as needed. It is useful for sequential work where different functions are performed progressively on the same workpiece.
• Turret Lathe. A turret lathe is equipped with a turret—an indexable tool holder—that can exchange different tools throughout a single operation to quickly perform different functions on the same part.
• Turret Milling Machine. A vertical mill with a stationary cutter and a workpiece that moves along the X and Y axes while being cut.
• Tuyere. A pipe or tube through which air is forced into the fire of a hearth or furnace.
• Two-Roll Rolling Machine. Commonly called just a “2-roll,” it is a type of sheet metal roll that features only two rolls instead of the common three or four. While some very small gauge 2-roll machines utilize two rigid rolls, many are motorized rolls with an inflexible upper roller that pushes down into a pliable bottom roll. The bottom roll, which is usually covered in a material such as polyurethane or neoprene, conforms to the shape of the top roll, giving bottom support to the material across an arc and not just at a single point.