Locating Devices 121

accurate

Conforming closely to a given standard. Accurate surfaces closely match the required tolerance and surface finish for a part.

adjustable locators

A locating component that can vary in length or position. Adjustable locators may be threaded in order to move to accommodate workpieces of different sizes.

aluminum

A lightweight metal that is silvery white in color. Aluminum resists corrosion and is easy to machine.

assembled locators

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

bevels

An edge or surface of a locator that is set at a sloping angle. Bevels reduce the amount of locator in contact with a workpiece to prevent binding and provide space for chips and swarf to exit the work area.

binding

The sticking or wedging of a workpiece on a locator. Binding requires additional manufacturing time to separate the workpiece and locator, sometimes causing damage to one or both.

body

The portion of a locating device that sits above the fixture and holds the locator's head. The body of the locator rests against the surface of a workpiece.

bullet pins

A type of fixture locating device with an elongated round head. Bullet pins help prevent hole binding when used for internal location.

carbide

A compound formed by combining carbon with other elements such as chromium, tungsten, or titanium. Carbide has high hardness and wear resistance, making it well suited for gripping face inserts.

Cartesian coordinate system

A positioning method that uses three linear axes perpendicular to each other to describe the location of an object in three-dimensional space. The Cartesian coordinate system is used to precisely position a workpiece.

cast iron

An alloy of iron, carbon, and silicon that contains at least 2% carbon. Cast iron is a hard, heavy material used for making some V-locators.

chamfers

A small, angled surface added to part of a locator's edge. A chamfer removes the sharp edge and provides space between the locator and the workpiece for chips and swarf to escape.

chips

A small piece of material that is removed from a workpiece. Chips can get caught between fixture components and the workpiece, reducing finished part accuracy.

clamping

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

clamps

A workholding device that tightens to hold a workpiece against locators during manufacturing operations. Clamps include strap clamps, screw clamps, and toggle clamps.

clearance

An intentional amount of space left between two components. Clearance is often required to prevent swarf and chip build-up during cutting or other manufacturing operations.

concentric location

A type of location in which the locator is set inside a centrally located hole or around a cylindrical workpiece. Concentric location restricts 9 degrees of freedom with a single locator.

conical pins

A type of fixture locating device with a cone-shaped head. Conical pins are internal locating devices used when a series of workpieces have a range of hole tolerances.

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.

deformation

The change in an object's size or shape as a result of stress. Deformation can occur in workpieces that are exposed to excessive manufacturing forces without proper location and support.

degrees of freedom

The possible directions of movement for an object. Restricting as many degrees of freedom as possible is necessary in workholding.

diamond pins

A type of fixture locating device with a polygon-shaped head. Diamond pins are used as internal locators to restrict workpiece rotation.

dowel pins

A solid, short, cylindrical rod used as a type of fixture locating device. Dowel pins are the most commonly used external locating device.

equalizing locators

A locating or support component with two heads that each move based on the position of the other head. Equalizing locators are best suited for irregularly shaped parts or parts with irregular surfaces.

external location

The process of restricting workpiece movement by placing locators on outside workpiece surfaces. External locating is more commonly used for flat or cylindrical workpieces with no holes.

fasteners

A device that holds objects together or locates them in relation to one another. Common fasteners include bolts, screws, pins, and rivets.

fixed locators

A stationary locating component. Fixed locators provide stable and rigid setups.

fixture feet

A locating component used on the bottom of a fixture to raise it to the proper height. Fixture feet are usually locating buttons or other similar modular components.

fixture leg plates

A locating pad used to raise a fixture to the correct height. Fixture leg plates provide additional stability when raising a fixture.

fixture plate

A component that provides the base for the other elements of a fixture. Fixture plates 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 fixture plate. Fixtures are useful when holding irregularly shaped workpieces or when holding multiple workpieces for a single operation.

flat-head pins

A type of fixture locating device with a smooth, level top. Flat-head pins are used for external and internal location.

friction

A force that resists motion between two components that are in contact with one another. Friction helps locators better secure workpieces.

full locating nests

A fixed locator that completely surrounds the outside surface of a workpiece. Full locating nests are used for workpieces with irregular features.

gripping faces

A textured surface on a locating device that resists workpiece movement. Gripping faces, which can be inserts or part of the face, are useful in operations with large manufacturing forces.

head

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

inserts

A removable or fused component used in some locating devices. Inserts come in different materials for different applications.

integral locators

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

internal location

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

knurled

Formed with a patterned series of grooves or diamond-shaped marks. Knurled surfaces are added to locators to create gripping faces.

linear

Extending indefinitely along a straight line. Linear movement includes up and down, left and right, and back and forth motion.

locating

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

locating buttons

A fixture locating component with a wide head. Locating buttons, or rest buttons, fit in holes on fixture plates and provide a broad area for the workpiece to rest against.

locating nest

A fixed locator that surrounds the outside surface of a workpiece. Locating nests are pockets machined directly into the surface of a fixture plate.

locating nests

A fixed locator that surrounds the outside surface of a workpiece. Locating nests are pockets machined directly into the surface of a fixture plate.

locating pads

A thick, wide locating component with a large surface area for workpiece contact. Locating pads, or rest pads, provide excellent support and motion resistance against extreme manufacturing forces.

locating pin

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

locators

A fixture component that positions the workpiece and restricts its movement. Locators include locating pins, blocks, and nests.

lock nut

A type of nut that screws down on top of another nut or material to hold the first one in place. A lock nut holds certain adjustable locators in place.

locking screw

A threaded component that holds another component in place when tightened. Locking screws on locating devices generally hold the shank in place.

machined

Shaped through a manufacturing operation such as metal cutting. Machined surfaces are more even and smooth than unmachined surfaces.

marring

The infliction of surface damage to a workpiece. Marring can occur on workpieces if they are exposed to excessive manufacturing forces and locating devices that are too hard.

mount

A threaded device used to support a threaded locator or fastener. A locator mount is used with adjustable locators.

partial locating nests

A fixed locator that partially surrounds the outside surface of a workpiece. Partial locating nests are less time consuming to make.

pin shaft

The cylindrical part of a locator pin that extends below the head to the end of the pin. A pin shaft is typically placed in the hole of a fixture plate.

pivot

A central point around which a component swings or rotates. Pivots allow components to move in precise relationships to one another.

plane

A flat, level surface. Planes are used for external location in fixture design.

plane location

A type of external location in which locators are set against several flat surfaces on the workpiece. Plane location is the most common form of external location.

positive stops

A solid component that prevents the movement of another object. Positive stops on fixtures are the locators and supports.

press-fit shanks

A feature on a locator that allows it to be placed in a fixture plate using simple downward pressure. Press-fit shanks should be just slightly smaller than the fixture plate hole to fit securely.

pressure

The exertion of mechanical force on an object. Pressure is created as a lateral force when spring-stop buttons and spring pins press against the workpiece.

radial location

A type of location in which one locator is set inside a centrally located hole and additional locators are set in or around another feature. Radial location restricts 11 degrees of freedom with two or three locators.

radial locators

A locator used to restrict rotational movement. V-locators can be used as radial locators.

referenced

Capable of locating a tool, workpiece, or machine component in a known position. A properly referenced workpiece improves the accuracy of cutting operations.

relieved

Machined to have an angled or narrower surface to create space or a gap between components. Relieved locators have additional space for chips to escape and reduce the amount of surface area in contact between the workpiece and locator.

repeatable

Capable of positioning workpieces in the same place, part after part, to be machined consistently within their required tolerance. A repeatable process is crucial for the efficient, quality production of identical parts.

rest

An accessory used on a fixture plate that provides support for workpieces. Rests reduce workpiece vibration and movement.

rest buttons

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

rest pads

A thick, wide locating component with a large surface area for workpiece contact. Rest pads, or locating pads, provide excellent support and motion resistance against extreme manufacturing forces.

rotational

Moving or extending in a circular path around an axis. Rotational movement can occur in both clockwise and counterclockwise directions around a linear axis.

round pins

A locator pin with a smooth, symmetrical dome at its head. Round pins allow smooth rotation that prevents binding when used as concentric locators.

service life

The amount of time a tool is able to perform its intended function. Service life for a tool varies depending on the frequency of its use and the forces involved in its operation.

setups

The position of tooling and fixturing for a machining operation. The workholding setup for a part directly affects the quality of the machining.

shank

The cylindrical portion of a locating device that extends from the underside of the head to its end. Shanks come in a variety of styles, such as press-fit, solid, or threaded, to work with a variety of fixture plates or mounts.

sheet metal

Flat metal stock that is no greater than 0.25 inches (0.64 centimeters) thick. Sheet metal requires more support during machining processes due to its thickness.

shoulders

A ring, collar, or flat step on a locating device. Shoulders on locating devices extend beyond the width of the head to provide a surface on which the workpiece can rest.

spherical

Shaped with a symmetrical domed surface. Spherical pins fit well into curved surfaces.

spring pins

An adjustable locator with a pin attached to a spring. Spring pins adjust to fit the workpiece as it is loaded and moves back to press against the side of the workpiece after loading.

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.

spring-stop buttons

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.

steel

An alloy of iron and carbon containing less than 2% carbon. Steel is a common material used for machining locating devices.

supporting

Reinforcing a workpiece around its exterior or from underneath. Supporting a workpiece helps prevent workpiece deformation.

supports

A fixture 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 texture or roughness on the surface of a part after it has been manufactured. Surface finish varies, depending on the machining process.

swarf

The gritty combination of chips, abrasive grains, and worn bonding material that is produced during machining. Swarf can damage a workpiece surface or the locating device if not given space to leave the work area.

swivel faces

A movable face on a locating device that can shift to match a sloping surface. Swivel faces are useful in operations with irregularly shaped workpieces.

symmetrical

Having completely identical features on either side of a point, line, or plane. Both sides of a symmetrical part have the same dimensions.

textured

Having visual or tactile surface characteristics. Textured buttons are rough and help to better grip a workpiece.

threads

A long, spiraling ridge around the interior or exterior of a cylindrical part. Threads allow compatible objects to be joined gradually and predictably.

tolerances

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

T-slots

A T-shaped opening that runs the length of a fixture plate. T-slots enable machinists to clamp vises and other workholding components onto the fixture plate.

urethane

A polymer that is used as a coating for its strength and versatility. Urethane inserts in locating devices provide durability without harming the surface of soft metals.

V-blocks

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

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-locators

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

wear

The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

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 devices

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

workpiece

An unfinished part that is subjected to one or more manufacturing operations in order to create a finished product. Workpieces can be shaped and finished through various manufacturing operations, such as metal cutting and assembly.

worktable

The machine component that supports the workpiece and any workholding devices during machining. The fixture plate clamps onto the worktable.