Common Terms in the Screw Machining Industry

Term Definition
American-type single-spindle screw machine A modified automated lathe distinguished by a turret that approaches a workpiece from the axial orientation.
automatic bar machine A turning machine that continuously cuts a number of parts from a piece of bar stock, one after another. The bar stock advances through the spindle and is held by the collet during the operation. A bar machine is traditionally called a screw machine.
axial approach A tool approach that runs parallel to the axis of a workpiece. Also called the parallel orientation.
bar stock Raw material purchased from metal manufacturers in the form of long bars. Bar stock may be round, square, or hexagonal.
bar stock magazine A chamber that allows the feeding of bar stock, one at a time, into a machine.
boring The process of using a single-point tool to enlarge a preexisting hole.
bushing A guide for bar stock on the Swiss-type single-spindle screw machine that enables the creation of very small parts with excellent tolerances.
cam A circular or cylindrical machine component that converts rotational movement into linear movement. A cam controls the feed rate and depth of cut of cutting tools on the automatic bar machine.
chip An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal.
chuck A device that holds a workpiece in place as it rotates. The chuck commonly has three or four jaws that can be adjusted to fit various sizes of parts.
chucking machine A general name for any lathe that uses a chuck to hold the part. An operator must load and unload each individual workpiece.
CNC turning center A sophisticated CNC machine that specializes in turning, boring, drilling, and threading operations, all at the same location.
collet A slitted device that holds a workpiece in place as it rotates. A collet has a hole through which the workpiece passes, and it is designed to hold specific dimensions. Collets can also be used to hold cutting tools.
computer numerical control A sophisticated machine tool that uses a computer and special programs to carry out various machining operations. The turning center is an example of a lathe equipped with computer numerical control (CNC).
cross slide On a lathe, the tool-holding components that allow tools to approach a workpiece from a perpendicular, or radial, orientation.
cutoff An operation performed on the lathe that uses a cutting tool to separate a finished part from the rest of the stock.
cycle time The time it takes to make one part.
depth of cut The amount of material that is removed with one pass of a cutting tool.
drilling The process of using a multi-point tool to penetrate the surface of a workpiece and make a round hole.
drive shaft Located in the base of a turning machine, the device that transfers power from the motor to all machine components.
engine lathe The original and most basic type of lathe.
facing An operation performed on a lathe that feeds a single-point tool across the end of a cylindrical workpiece to create a flat surface.
feed The linear movement of a cutting tool into a part to remove material.
follower A machine component that traces the outline of a cam and thus controls the way a workpiece is cut.
form turning An operation performed on a lathe that feeds a tool into a workpiece in order to impart the tool's shape in the workpiece.
headstock The end of a lathe that holds the spindle and the drive that rotates the workpiece.
horizontal axis An imaginary line that passes through the center of an object and is parallel to the floor.
ID grooving The process of cutting an internal channel or passageway into a drilled hole.
index The changing of machine components to a different position.
inner-diameter operation A cutting operation that takes place on the interior surface of a cylindrical workpiece.
lathe A machine tool commonly used to create cylindrical parts. A lathe holds a cylindrical workpiece on one or both ends. The cutting tool is gradually passed along the surface of the rotating part.
machine motor The primary source of power that is located in the base of a lathe.
mechanical safety clutch A safety device that disengages the drive shaft from the motor.
multiple-spindle screw machine An automatic bar machine that contains more than one spindle, usually 4, 6, or 8. Multiple spindles allow multiple tools to cut multiple workpieces simultaneously.
OD chamfering An operation performed on a lathe that feeds a tool to create an angled edge on the workpiece.
OD threading An operation performed on a lathe that cuts a long, spiraling ridge down the outer surface of a workpiece.
outer-diameter operation A cutting operation that takes place on the outer surface of a cylindrical workpiece.
radial approach A tool approach that runs perpendicular to the axis of a workpiece. Also called the perpendicular orientation.
reaming The process of using a multi-point tool to smooth the interior surface of a hole.
screw machine An automated turning machine that continuously creates a number of finished parts from bar stock. Bar stock advances through the spindle and is held by a collet. It is also commonly called a bar machine.
setup Time that is spent setting up the fixtures and tooling, calculating tool offsets, and performing all the necessary tasks to produce the first accurate part.
single-point cutting tool A cutting tool that uses a single cutting edge to remove material.
single-spindle screw machine An automatic bar machine that contains one spindle. The spindle rotates one piece of bar stock, which is cut by one tool at any given time.
spindle The part of the machine tool that spins. On a screw machine, the spindle holds the workpiece.
Swiss-type single-spindle screw machine A modified automated turret lathe distinguished by a sliding headstock and fixed bushing. Swiss-type machines are capable of creating very small parts with excellent tolerances.
tailstock A device located at the end of a lathe opposite the headstock that supports the end of longer workpieces.
taper turning An operation performed on a lathe that feeds a tool at an angle to the length of the workpiece in order to create a conical shape.
tapping The process of cutting internal threads in a workpiece with a multi-point tool.
tolerance An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.
turning A machining operation used to make cylindrical parts. A single-point cutting tool passes along the outer surface of a cylindrical workpiece as it rotates and gradually removes a layer of material.
turret The component of a lathe that holds a number of cutting tools. The turret rotates to place tools in the cutting position.
turret lathe A lathe with a mounted device that holds multiple cutting tools. The turret rotates to position one specific cutting tool in place after another.
vertical turning machine A turning machine in which the spindle is perpendicular to the ground floor. Vertical turning machines are often used for very large or heavy parts.
workholder A device used to locate and hold a workpiece in place.