Introduction to Workholding 101

adjustable locators

A locating component with moving parts. Adjustable locators can move to accommodate workpieces of varying sizes.

angle plate

A workholding device that consists of two surfaces connected at a 90° angle. Angle plates can securely hold rectangular workpieces or raise a workpiece from the worktable surface.

assembled locators

A separate locating component that is attached or fastened to the fixture or other workholding device. Assembled locators provide more setup flexibility but are less rigid.

assembly

A manufacturing process in which two or more components are joined together to create a finished part. During assembly a workholding device holds components in the proper location for accurate joining.

bar feeding machine

A device that continuously extrudes a long piece of bar stock at a steady rate. Bar feeding machines can be used with lathes and collets to quickly create a series of individual parts.

bar stock

Raw material purchased from metal manufacturers in the form of long bars. Bar stock may be round, square, or hexagonal.

base plate

A flat, rectangular fixture body with holes, slots, or both to allow the placement of fixture components. Base plates are set on a machine worktable for milling, drilling, or grinding operations.

bushings

A hardened metal tube, either fixed or removable, that is used to constrain or guide tools or to reduce friction. Bushings are used in jigs to guide cutting tools such as drills and reamers.

cams

A rotating circular surface used to transmit motion. Cams can be used to lock clamps into place.

changeovers

The process of switching a machine tool or workholding device from one setup to another for a different operation. Changeover speed can be improved through the use of power clamping for workholding.

chucks

A circular workholding device that secures a workpiece as it rotates on a lathe or other machine. Chucks commonly have three to four adjustable jaws that can be moved to clamp and secure a variety of workpiece shapes and sizes.

clamping

Securely holding a workpiece against locators. Clamping a workpiece helps it resist the cutting forces that occur during machining.

clamping forces

The compressive force that holds a workpiece in place. Clamping forces resist the cutting forces created as the tool moves along, around, and in the workpiece.

clamps

A fixture or jig component that tightens to hold a workpiece in place when it is exposed to the cutting forces of manufacturing. Clamps include strap clamps, screw clamps, and toggle clamps.

collar

A circular component that surrounds and supports another component. Collars include the openings on collet faces, which surround and grip a workpiece during manufacturing operations.

collets

A cylindrical workholding device with slits on its sides used to hold small, fragile, or thin-walled workpieces. Collets come in a variety of sizes and generally have a center hole that fits a workpiece of a certain dimension.

columns

A special type of pillar-shaped tombstone fixture with four, six, or eight sides. Columns can hold workpieces or vises on all their sides.

crank

A metal rod or rotating wheel used to open or close a vise. Cranks, or handles, shift the movable vise jaw along a screw.

cutting fluid

A fluid used to cool, lubricate, and clear chips during a material removal process. Cutting fluid, or coolant, can improve tool life and finished part quality when used correctly.

cutting forces

The various stresses involved in a machining process. Cutting forces are determined by a combination of speed and feed rate, tool angle, workpiece material, and other factors.

cutting tool

A device with one or more edges used to remove material, which creates chips. Cutting tools are either single-point or multipoint devices.

datums

A point of reference for machine tools, programs, and fixtures from which measurements are taken or positions are located. A datum can be a hole, line, or any three-dimensional shape.

destructive testing

A part assessment method that places materials in harsh conditions that lead to part failure. Destructive testing, such as the guided bend test and transverse tension test, uses the application of force, meaning parts undergoing the tests must be held securely through workholding.

diameters

The distance from one edge of a circle to the opposite edge going through the center. Diameter describes the size of round and cylindrical workpieces and tools.

drill plates

A jig component with a flat surface and carefully positioned holes. Drill plates guide the cutting tool in placing holes of the correct size and shape.

drill presses

A machining tool with a multipoint cutting tool that penetrates the surface of a workpiece and makes a round hole. Drill presses can be used for a variety of holemaking operations.

drilling

A machining operation in which a multipoint tool is fed into a workpiece to create a round hole. Drilling is often used as the first step in a hole-making process, followed by more precise procedures such as boring and reaming.

external locating

The process of restricting workpiece movement by placing locators on outside surfaces. External locating is most commonly used for parts with flat outside surfaces and no holes.

faceplate

A circular body fixture with holes, slots, or both to allow the placement of fixture components. Faceplates are primarily used for lathe operations.

fasteners

A device that holds two or more objects together. Common fasteners include bolts and screws.

finishing

A final process performed to complete a part. Finishing operations surface, condition, edge, and clean parts and are usually the last steps in the machining process, occurring before inspection and testing.

fixed locators

A locating component that has no moving parts. Fixed locators provide stable and rigid setups.

fixture bodies

A component that provides the base for the other elements of a fixture. Fixture bodies include faceplates for lathes and base plates, angle plates, and tombstones for milling and drilling.

fixtures

A customizable, modular workholding device created by configuring locators, supports, and clamps on a body fixture. Fixtures are useful when holding irregularly shaped workpieces or when holding multiple workpieces for a single operation.

fulcrum

A central point on which a mechanism turns or swings. Fulcrums, or pivot points, may be physical objects or just points in space.

grinding

A machining process in which an abrasive is used to precisely cut and shape the surface of a workpiece. Grinding operations may use chucks, collets, or vises as workholding.

handle

A metal rod or rotating wheel used to open or close a vise. Handles, or cranks, shift the movable vise jaw along a screw.

heads

The component on a support or locating device upon which the workpiece rests. Heads can be flat, conical, rounded, or hemispherical, among other shapes.

holemaking

The process of machining a hole into the interior surface of a workpiece. Holemaking can be accomplished by drilling, tapping, boring, reaming, or a combination of those operations.

honing

A finishing process that uses abrasive stones to grind away small amounts of workpiece material. Honing is used to create high quality surface finishes and tight tolerances.

hydraulic clamping

A clamping system that uses the power created from compressed liquid to create the gripping force for clamps to hold a workpiece in place. Hydraulic clamping is generally used with larger workpieces over pneumatic clamps because the equipment takes up less space.

independent chucks

A round lathe workholding device with jaws that open and close individually. Independent chucks require more operator intervention but center workpieces more precisely than self-centering chucks.

indexing

Moving a workpiece or machine component to another location in a fixed, controlled increment. Indexing allows for the precise machining of similar features in regular places on a part.

indexing fixtures

A workholding device that secures a workpiece and moves it in precise increments. Indexing fixtures can be used to cut a variety of part features at regular intervals on a workpiece.

indexing head

A machine tool that features a handle, plate, and gear system that allows operators to position and index a workpiece in an indexing fixture. Indexing heads use the handle to move the gears that move the workpiece, while the plate has holes that allow operators to assess workpiece movement exactly.

indexing jigs

A workholding device that guides the manufacturing tool, secures the workpiece, and moves either the tool or workpiece in precise increments. Indexing jigs are often used to drill holes around the surface of a cylindrical or round workpiece.

indexing workholding devices

A workholding device that, in addition to securing the workpieces, allows operators to place features on the workpiece at precise intervals. Indexing workholding devices control tool movement, workpiece movement, or both.

inspection

The examination of a part to determine if it conforms to necessary specifications and measurements. Inspection traditionally follows the completion of a part or there may be inspection of the components of a part prior to and after assembly.

inspector

A person who examines a part with various tools and techniques to determine its conformance to specifications. An inspector assesses the accuracy of a part and whether it meets its specified tolerances.

integral locators

A locating component that is built into or permanently fixed to the fixture or other workholding device. Integral locators are always fixed and provide highly stable and rigid setups.

internal locating

The process of restricting workpiece movement by placing locators on inside surfaces. Internal locating is more efficient and accurate than external locating.

jaws

The component on a chuck that makes contact with and holds the workpiece. Jaws on a chuck help support, secure, and locate the workpiece.

jigs

A customizable, modular workholding device that supports, locates, and clamps a workpiece and also directs the cutting tool. Jigs are often used to hold irregular parts and generally decrease machine tool setup time as they provide guidance for tools.

lathes

A machine used to create parts, often cylindrical, by removing material from a workpiece. A lathe holds a rotating workpiece while the cutting tool is either fed into the workpiece or along its side.

layout

A manufacturing process during which a workpiece is marked with lines, centers, or circles to show how it should be machined or during which the component parts of a part are arranged for assembly. Layout occurs prior to the actual machining and assembly processes.

locating

Establishing a workpiece in a set position. Locating a workpiece correctly ensures it will be machined or otherwise manufactured to the correct specifications and tolerance.

locating nest

A fixed locator that partially or completely surrounds the dimensions of a workpiece. Locating nests are machined directly into the surface of a fixture body.

locating pin

A cylindrical component, sometimes with a shaped head, used on fixtures to restrict workpiece motion and position the workpiece. Locating pins are one of the most commonly used fixture locating components.

locators

A workholding device used to position a workpiece within a jig or fixture. Locators establish a relationship between the workpiece and the workholding device.

machine tool

A power-driven machine that is used to manufacture parts by guiding a tool to shape workpieces. Common examples of machine tools include the drill press, the lathe, and the mill.

machining

The process of removing material to form, shape, or finish a part. Machining processes include turning, drilling, and milling.

manual machine

A machine tool that is operated by the actions of the machine operator, rather than by automated or computerized actions. Manual machines are less expensive than computer numerical control (CNC) machines but also less precise and efficient.

mill

A machine that uses a multipoint milling cutter to perform various cutting operations. Mills, or milling machines, are commonly used to machine slots, grooves, and flat surfaces in rectangular workpieces.

milling

A machining operation that uses a rotating multipoint cutter to remove metal from the surface of a workpiece. Milling operations commonly use vises as workholding.

milling machine

A machine that uses a multipoint milling cutter to perform various cutting operations. Milling machines, or mills, are commonly used to machine slots, grooves, and flat surfaces in rectangular workpieces.

modular

Consisting of interchangeable and discrete parts. Modular workholding devices, such as some jigs and fixtures, can be configured to fit a wide range of parts, including those with irregular features and dimensions.

nut

A fastener with a hole and internal threads that mates with a bolt or screw. Nuts can serve as the head for support and locating fixture components.

operators

A person responsible for running a machine properly, safely, and efficiently. Operators are often responsible for, among other duties, correctly securing the workpiece in a workholding device.

parallel

Two lines or objects that are equidistant from each other. Parallel lines or objects will never intersect.

parallels

A pair of identical support blocks. Parallels help reinforce and raise workpieces in a variety of milling, drilling, and grinding operations.

part print

A document containing all the instructions necessary to manufacture a part. A part print, or blueprint, includes a part drawing, dimensions, and notes that will describe the order and type of manufacturing operations and important part specifications.

part run

A series of identically shaped finished products. Part runs require accurate and repeatable workholding to ensure consistency.

perpendicular

An intersection of two lines or objects at a right, or 90°, angle. Workpieces perpendicular to the worktable will be set on their sides.

pivot pin

A component in a toggle clamp about which the head and lever rotate. The pivot pin in a toggle clamp allows for easy adjustment of the head and allows the lever to lock the head in place.

plating

The process of adding a thin layer of metal to serve as a decorative or protective coating on a part. Plating is used to improve the appearance or functionality of parts.

pneumatic clamping

A clamping system that uses the power created from compressed gas, usually air, to create the gripping force for clamps to hold a workpiece in place. Pneumatic clamping is preferred for smaller workpieces because the equipment required to compress gas can take up space.

power clamping

A clamping system that uses a means other than manual power to secure the clamps. Power clamping generally uses hydraulic or pneumatic systems.

pressure

The exertion of mechanical force on an object. Pressure is created, usually as a downward force, when a clamp is tightened against a workpiece.

reaming

The process of enlarging an existing hole with a multipoint tool. Reaming is performed to improve the surface finish and concentricity of a hole.

repeatability

The ability of a workholding device to position workpieces in the same place, part after part, for a part run. Repeatability is crucial for the efficient, quality production of identical parts.

rest buttons

A fixture support or locating component with a flat, circular head. Rest buttons fit in holes on fixture bodies and provide a broad area for the workpiece to rest against.

rigid

Stiff and inflexible. Rigid machine setups reduce issues such as vibration and lead to better tolerance and surface finish on a part.

rotational

Circular motion around a fixed axis. Swing clamps are capable of rotational movement which makes them easy to move into and out of place.

self-centering chucks

A round lathe workholding device with jaws that open and close in unison. Self-centering chucks, or scroll chucks, automatically center workpieces, though with less accuracy than other workholding, such as independent chucks.

serrated

Having a series of connected, usually similarly sized, jagged edges. Serrated edges on toe clamps give them a firmer grip.

setup

The position of tooling and fixturing for a machining operation. The setup of a machine for manufacturing will affect the proper setup of workholding.

sleeves

A tubular metal part designed to fit over another component. Sleeves include collets, which are hollow metal tubes that fit over a workpiece.

slots

A narrow channel in the surface of a part or component. Slots allow engineers to move and attach fixture components to fixture bodies and, on collets, permit opening and closing of the workpiece opening.

specifications

A description of the essential physical and technical properties of a finished part. Specifications outline important information including finished part dimensions and how the part must respond to forces acting upon it.

spindle

The part of the machine tool that spins or rotates. On the mill, the spindle holds a cutting tool, while on the lathe, the spindle holds the workpiece.

spring locating pin

An adjustable locator with a bulb attached to a spring. Spring locating pins raise the workpiece slightly from the fixture body to provide clearance for chips.

spring plunger

A fastener or locking device with a pin, spring, and knob. Spring plungers fit into a hole with the pin, move and snap into place with the spring, and lock and unlock with the knob.

springs

A flexible device made of coiled material that yields under force and returns to its original shape once the force is removed. Springs are used in some adjustable locators to allow movement of the locator.

spring-stop button

An adjustable locator with a flat head attached to a spring. Spring-stop buttons automatically adjust their size when a workpiece is pressed against them.

strap clamp

A fixture or jig clamping device that consists of a metal bar that exerts pressure on the workpiece and a device to hold the bar in place. Strap clamps use either fasteners or cams to exert pressure against the workpiece.

supporting

Reinforcing a workpiece around or from underneath. Supporting a workpiece helps prevent workpiece deformation and locates the workpiece.

supports

A fixture or jig component that provides reinforcement to the workpiece during machining to prevent it from breaking or deforming. Supports include rest buttons, support pins, and centers.

surface finish

The degree of roughness and variation on the surface of a part after it has been manufactured. Surface finish can be damaged by excessive pressure from clamps, vibration against fixture components, or improper securing and location.

swing clamp

A fixture or jig clamping device that rotates around a fixed axis. Swing clamps allow for easy loading and unloading of workpieces.

tapping

The process of cutting internal threads in a round hole with a multipoint tool. Tapping can be performed on a manual mill or a drill press.

testing

The examination of a part to ensure that it performs its intended function. Testing evaluates whether the part can safely and effectively perform its required function based on part specifications.

threaded adjustable locator

A locating device with a spiraling groove and a component, usually the head, that travels around that groove. Threaded adjustable locators can be adjusted to fit a range of workpiece sizes.

threads

A long spiraling groove machined in the interior or exterior of a part. Threads allow compatible fasteners to connect to and move about each other.

toe clamp

A fixture or jig clamping device that grips a small portion of the workpiece with a large amount of pressure. Toe clamps are useful for workpieces with small clamping surfaces or to provide more access for the cutting tool.

toggle clamp

A fixture or jig clamping device that operates using a fulcrum and lever system that allows operators to easily clamp, unclamp, and adjust the clamp. Toggle clamps can quickly adjust to workpieces of varying sizes.

tolerances

An unwanted but acceptable deviation between an actual part dimension and its intended design. Tolerances are assessed during the inspection stage of manufacturing.

tombstones

A vertically oriented rectangular fixture that can hold workpieces on two different surfaces. Tombstones are often used to machine a series of workpieces at the same time.

turbine

A machine that uses the motion or energy of water or wind to produce circular movement that generates energy. Turbines are often large and need to be manufactured using customized chucks.

turning

A machining operation in which a workpiece is rotated on a lathe while a single-point tool is guided along the workpiece. Turning is one of the most common machining operations and often uses chucks and collets as workholding.

vibration

A rapid, continued, repeated motion in a machine or other structure. Vibration is caused by small shifts in the workpiece that can negatively affect tolerance and surface finish.

vise

A workholding device with two jaws, usually one fixed and one movable, that grip and hold a workpiece in place. Vises are often used to hold workpieces for milling, drilling, or grinding operations.

v-locator

A fixed locator that has an angled, notched interior in the shape of a "v." V-locators are used to position and center cylindrical workpieces for milling and drilling.

welding

A joining process that uses heat, friction, or a combination of methods to fuse two materials together permanently. Welding is used in a variety of industries from auto manufacturing to aerospace engineering.

workholding

The process of securely supporting, locating, and clamping a workpiece for a manufacturing operation. Workholding helps to ensure that parts are created accurately and with good repeatability.

workholding device

A device used to secure, support, and locate a workpiece during a manufacturing operation. Common workholding devices include chucks, collets, and vises, among others.

workpiece

A part that is being machined or is to be machined. A workpiece may be subject to cutting, grinding, forming, welding, or other operations to produce a finished part.

worktable

A component on a mill that supports the workpiece and any workholding device during machining. Worktables on the mill have T-slots that allow operators to attach a range of workholding devices, including already assembled fixtures or individual fixture components.