Benchwork and Layout Operations 241

abrasion

The wearing away or gradual removal of material from an object’s surface. Abrasion can create a smooth or refined surface.

adjustable hand reamer

A type of hand reamer that expands and contracts slightly to sizes within a small range. Adjustable reamers are often used for oddly sized holes.

angle

A figure formed by the intersection of two lines. Angles are also used to measure distances around a circle.

automated

Any system, machine, tool, or device that does not require human intervention. Automated engraving machines are often used for engraving complex symbols and high volume production.

ball peen hammer

A type of hammer with a round end and a flat end used to tap the prick punch into the workpiece. Ball peen hammers are also known as machinists’ hammers.

benchwork operations

Any additional process performed on a workpiece before or after it is machined. Benchwork operations are generally manual, such as hand tapping and hand reaming.

blind hole

A hole that begins on one side of a workpiece and ends inside the workpiece. Blind holes do not extend through the entire thickness of a workpiece, so they only have one opening.

blueprint

A document containing all the instructions necessary to manufacture a part. A blueprint includes a part drawing, dimensions, and notes.

bottoming tap

A type of hand tap that has 1 to 1 1/2 tapered threads. Bottoming taps are the last tap used when hand tapping blind holes.

bushing

A hardened steel tube that guides drills, reamers, and other cutting tools. Bushings ensure a cutting tool enters a drilled hole at the correct angle.

caliper rule

A measuring instrument with a pair of expandable jaws on one end and a beam containing a marked scale of unit divisions. Caliper rules can measure both internal and external features.

carbon tool steel

A type of steel designed with improved wear resistance, toughness, and strength. Hand reamers are commonly made of carbon tool steel.

center drilling

A process in which a rigid drill precisely locates a hole in the center of a workpiece. Center drilling establishes a hole’s true centerline diameter.

center head

A component of a combination set used for layout. Center heads allow machinists to find the center of round or cylindrical workpieces.

center punch

A tool used to mark small, sharp points along layout lines. Center punches create small indentations that indicate the centers of holes when preparing for drilling operations.

chamfer

An angled surface that eliminates a sharp corner, removes burrs, and/or aids in assembly. Chamfers generally replace a 90° angled surface with a 45° angled surface.

chamfering

A type of benchwork operation that involves manually removing a sharp corner or edge from a workpiece by creating an angled surface. Chamfering generally turns a 90° angle into a 45° angle.

combination set

A multi-faceted measuring device that allows operators to lay out any size angle. A combination set consists of a protractor head, square head, and center head on a steel rule.

computer numerical control

CNC. A combination of software and hardware that directs the operation of a machine. Computer numerical control uses mathematical data to direct machine movements.

cutting fluid

A fluid used during cutting operations to reduce heat and friction between the cutting tool and the workpiece. Cutting fluids used in manual machining are often oil-based.

dimensions

A measurement of space, especially length, width, and height. Dimensions of a part are indicated on the blueprint.

dividers

A layout tool with two sharp-pointed legs used for spacing distances and scribing circles. Dividers have a spring-loaded adjusting screw that allows operators to expand or contract the legs.

drill press

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

drill press

A machining tool that uses a drill to penetrate the surface of a workpiece and make a round hole. Drill presses can be used for a variety of holemaking operations.

electrical discharge machining

EDM. A nontraditional machining process that erodes unwanted material from a workpiece using a rapid series of electrical sparks. Electrical discharge machining can be used to remove a tap that has broken inside a hole.

engraving

A type of benchwork operation that involves manually cutting thin lines into a metal workpiece to create letters, numbers, and symbols. Engraving is often used to create identification numbers on parts.

engraving machine

A machine that uses cutting tools, lasers, or other methods to carve letters, numbers, and symbols into a workpiece surface. Engraving machines are computer numerically controlled.

engraving pen

A thin hand tool that carves letters, numbers, and symbols into a workpiece surface. Engraving pens are generally pneumatic tools.

expansion reamer

A type of hand reamer that expands slightly with a screw. Expansion reamers only expand and do not contract; the diameter expansion is permanent.

feed handle

A device attached to a machine that controls the movement of a component. Feed handles, or handwheels, move the table side to side and forward and backward on a manual mill.

file

A flat metal cutting tool with a large number of very small teeth. Files wear away workpiece material through abrasion.

file card

A tool that machinists use to manually remove chips from a hand file. File cards prevent chips caught in a hand file from scratching a workpiece surface.

filing

A type of benchwork operation that involves manually removing small amounts of workpiece material with a tool that has small, sharp teeth. Filing can smooth workpiece surfaces, remove sharp edges, and add a chamfer.

flutes

A helical recess that winds up the length of the body of a drill, end mill, and tap. Flutes allow for the removal of chips and the entrance of cutting fluids.

hand reamer

A manual cutting tool that smooths or enlarges existing holes. Hand reamers have a straight shank and a square tang, or peg, that can be gripped with a tap wrench.

hand reaming

A type of benchwork operation that involves manually removing small amounts of workpiece material to enlarge an existing hole. Hand reaming is performed on holes that require tight tolerances.

hand stamping

A process that impresses letters, numbers, and symbols into a workpiece. Hand stamping is often used to place identification numbers on parts.

hand stamping

A type of benchwork opreation that involves manually impressing letters, numbers, and symbols into a workpiece. Hand stamping is often used to place identification numbers on parts.

hand tap

A manual cutting tool that cuts internal threads into a drilled hole. Hand taps are typically held and driven into a hole by a tap wrench.

hand tapping

A type of benchwork operation that involves manually cutting an internal thread. Hand tapping is performed without the use of a machine tool.

heat treatment

Controlled heating and cooling processes used to change the structure of a material and alter its physical and mechanical properties. Heat treating is often used to adjust a material’s hardness.

helical-fluted hand reamer

A type of hand reamer with spiral-shaped flutes. Helical-fluted hand reamers are often used to ream holes with keyways or interruptions.

high-speed steel

HSS. A common cutting tool material that is relatively inexpensive and offers excellent toughness. High-speed steel tools are often heat treated and coated.

keyways

A rectangular slot or groove that is machined down the length of a hole. Keyways make up the specific design of a keyhole.

layout

A type of benchwork operation that involves manually marking a workpiece with lines, centers, or circles prior to a machining process. Layout shows the size, shape, and location of features to be machined.

layout dye

A colored fluid that a machinist brushes or sprays on a workpiece at the beginning of layout. Layout dye allows surface marks to be seen more clearly.

lubricant

A substance used to reduce friction between components or objects. Machinist use lubricant to lengthen tool life and prevent marring of a workpiece surface.

major diameter

The distance from crest to crest of an external thread or from root to root of an internal thread. Major diameter is also called thread diameter.

manual bench tap

A device that aligns a hand tap with a hole for a hand tapping operation. Manual bench taps ensure the tap enters the hole straight.

manual mill

A machine that uses a rotating, multi-point cutting tool to remove material from a workpiece. Manual mills require an operator to control machine movements and adjust settings

mill

A machine tool that uses a rotating, multi-point tool guided along a workpiece to remove metal. Milling machines and milling cutting tools are commonly referred to as mills.

minor diameter

The distance from root to root of an external thread or from crest to crest of an internal thread. Minor diameter of a tap measures the farthest distance from root to root on opposite sides of the tool.

parallel

Two lines or axes that are equidistant from each other at all points along their length. Parallel workpiece surfaces never touch.

perpendicular

Meeting at a 90 angle. Perpendicular workpiece surfaces are considered square to one another.

pipe tap

A type of tapered tap that adds an internal thread to a pipe or tube. Pipe taps create tapered threads that improve the sealing capabilities of a tapped hole.

pitch diameter

The distance that separates points located in the grooves between threads. Pitch diameter is the theoretical point where a fastener’s threads meet a hole’s threads.

plug tap

A type of hand tap that has 3 to 5 tapered threads. Plug taps are often used after taper taps but before bottoming taps when hand tapping blind holes.

pneumatic tools

A tool that is powered by the motion and control of compressed air or gas. Pneumatic tools include engraving pens and screwdrivers.

precision steel square

A layout tool with two sides that form a 90° angle. Precision steel squares check the squareness of two surfaces to each other.

protractor head

A component of a combination set used for layout. Protractor heads allow machinists to mark or measure any size angle between 0 to 180 degrees.

scriber

A pen-like layout tool. Scribers create fine lines on the surface of a workpiece.

set screw

A type of screw with a rounded or cone-shaped end designed to fit into a matching recess. A set screw is used to expand an expansion reamer.

shank

A long cylindrical part of a tool or device, such as a drill or a reamer. The shank of a reamer has flutes.

square head

A component of a combination set used for layout. Square heads allow machinists to measure and scribe 45° and 90° angles.

stamps

A thin metal tool that has a raised mirror image of a letter, number, or symbol at one end. Stamps generally come in sets, so any desired combination of markings can be impressed into a workpiece surface.

steel rule

A simple measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Steel rules can be rigid or flexible.

straight-fluted hand reamer

A type of hand reamer with straight flutes. Straight-fluted reamers are the most common types of hand reamers.

straight-handle tap wrench

A type of tap wrench with a long, straight handle that usually holds large-diameter taps. Straight-handle tap wrenches are easier to turn because they provide a machinist with more leverage than other tap wrenches.

surface finish

The degree of smoothness of a part’s surface after it has been machined. Surface finish is the result of the surface roughness, waviness, and flaws remaining on the part.

tang

A square extension on the end of a reamer. Tangs allow reamers to be secured in tap wrenches.

tap drill size

Drill dimensions that are required to create a specific threaded hole. Tap drill size is the size of the drilled hole before it is tapped.

tap extractor

A tool that grabs the flutes of a broken tap to remove it from inside a hole. Tap extractors are held and turned by a tap wrench.

tap wrench

A manual tool that holds a hand tap’s square end and allows a machinist to turn the hand tap. Tap wrenches can also be used with hand reamers.

taper tap

A type of hand tap that has 8 to 10 tapered threads. Taper taps are the first tap used when hand tapping blind holes, and they are also often used to tap through holes.

tapered

Gradually decreasing in size from one end of the object to the other. Tapered taps create a conical shape at the bottom of a hole to fit screws.

T-handle tap wrench

A type of tap wrench that is shaped like a “T” and often used to hold smaller-diameter taps. T-handle tap wrenches require more force to manually rotate than other tap wrenches.

thread plug gage

A hardened, cylindrical ‘Go/No Go’ gage used to inspect the fit of threads in a hole. Thread plug gages are available in standardized sizes.

threads

A long, spiraling groove that may appear on a workpiece or tool surface. Threads help fasteners, such as screws, grip material and hold components together.

through hole

A hole that passes through the entire thickness of a workpiece. Through holes have no bottom because they pass through both sides of a workpiece.

tolerances

A blueprint specification indicating an unwanted but acceptable deviation from a given dimension. Tolerances state the allowable difference between a part and its intended design.

tool life

The length of time a cutting tool is expected to be operational before it must be replaced. Tool life can be extended through optimized implementation, including using the proper tool geometry or cutting with cutting fluids.

vernier

A small, movable, graduated scale used for measuring a fractional division of the fixed scale. Vernier scales appear on both manual calipers and micrometers.

vise

A workholding device with two jaws that grip and hold a workpiece in place. Vises used in benchwork operations have one fixed and one movable jaw.

workbench

A flat structure, similar to a table, that is used to perform manual cutting operations. Workbenches provide the surface and support for performing benchwork operations.

worktable

The machine component that supports the workpiece and any workholding devices during machining. Worktables may provide the surface and support for performing benchwork operations.