Tap Selection 390

abrasion resistance

A material’s ability to resist breaking due to friction from contacting another material. Metals with high abrasion resistance tend to have higher hardness.

abrasive

Consisting of hard particles that can wear away other materials. Abrasive workpiece materials can shorten tool life.

alignment

The accurate positioning of machine components. Alignment in tapping generally ensures that the tap and the hole share the same axis or centerline.

aluminum

A silver-white metal that is ductile, light, and thermally conductive. Aluminum is a soft metal that can be tapped using a high rake angle.

American National Standards Institute

ANSI. A nonprofit organization that establishes standards and guidelines for several industries and related processes and products in the United States. ANSI taps have short overall lengths and imperial shank diameters.

axis

An imaginary straight line that runs through the center of an object. A tap rotates around its axis.

basic

In thread limit notation, the pitch diameter of the tap. Basic is compared to the pitch diameter of the threads that the tap creates to determine the tap’s thread limit.

black oxide

A surface treatment used to add mild corrosion resistance to metals. Black oxide improves the performance of cutting fluid and reduces tool wear.

blind hole

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

bottoming tap

A type of tap with a short chamfer that has 1.5 to 2 tapered threads. A bottoming tap, also known as a type E tap, is used to cut threads near the bottom of a blind hole that has very little clearance between the bottom of the hole and the deepest required thread.

brittle

Hard and more likely to break instead of bend when subjected to force or pressure. Brittle tap materials include powdered metal and carbide.

carbide

A common cutting tool material developed by combining carbon with materials such as chromium, tungsten, or titanium. Carbide is used in metal cutting tools for its hardness and wear resistance.

carbide tipped

A tool material made mostly of high-speed steel with an outer layer of carbide. Carbide tipped taps offer the toughness of high-speed steel taps with added hardness from the carbide layer.

cast iron

A metal consisting of iron, more than 2% carbon, 1 to 3% silicon, and trace amounts of other elements. Cast irons are hard, brittle metals that should be tapped with a lower rake angle.

chamfer

The end of the land where the threads progressively increase in size. Chamfers gradually remove material and reduce tool wear.

chemical reaction

A process where the contact between one or more substances changes them into another substance or substances. Chemical reactions alter the physical structure of a substance.

chips

A piece of metal that is removed from a workpiece during a machining operation. Chips are tiny curls, shards, fragments, shavings, or particles of metal.

chromium

A shiny, hard, gray metal that increases corrosion resistance in metals. Chromium prevents the workpiece material from adhering to the cutting tool.

class of fit

A measure of tolerance that describes how well a fastener will engage with a threaded part. Classes of fit ensure a secure enough hold for the required application.

classes of fit

A measure of tolerance that describes how well a fastener will engage with a threaded part. Classes of fit ensure a secure enough hold for the required application.

clearance

An amount of space between two objects or components that is necessary to avoid contact. Clearance provided by the relief angle reduces friction between the tap and the workpiece.

CNC

Computer numerical control. A combination of software and hardware that directs the operation of a machine. CNC machines are much more precise than their manual counterparts.

coating

A thin layer of material added to the surface of a cutting tool. Coatings have a range of beneficial attributes, such as reducing friction and adding hardness to cutting edges.

cobalt

A hard, gray, brittle metal often used to create cutting tools. Cobalt is harder than high-speed steel and tougher than carbide.

combined drill and tap

A tool that can drill and tap a hole in a single motion. Combined drill and taps, also known as drill taps, cut down on production time by removing the need to switch tools between drilling and tapping operations.

computer numerical control

CNC. A combination of software and hardware that directs the operation of a machine. Computer numerical control machines are much more precise than their manual counterparts.

copper

A reddish metal that is very ductile, thermally conductive, and corrosion resistant. Copper is a soft metal that can be tapped using a high rake angle.

corrosion resistance

The ability of a material to resist deterioration and chemical breakdown due to surface exposure in a particular environment. Corrosion resistance in cutting tools can be improved through the use of coatings.

crests

The highest point on a thread. The crest size helps determine important thread measurements, such as pitch and diameter.

cutting edge

The leading face of a cutting tool that is in direct contact with the workpiece. The cutting edge performs the actual metal removal during a cutting operation.

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 speeds

The amount of workpiece material a cutting edge contacts in one minute. Cutting speed is measured in surface feet per minute (SFM) or meters per minute (m/min).

deformation

A change in the size or shape of a workpiece as a result of stress. Form taps use deformation to create threads in relatively soft workpieces.

DIN

Deutsche Institut fur Normung. An institute that creates manufacturing standards in Europe. DIN taps have long overall lengths and metric shank diameters.

DIN/ANSI

A type of tap that combines elements of DIN and ANSI standards. DIN/ANSI taps have long overall lengths and imperial shank diameters.

double nitride

A surface treatment method that heats metal within a nitrogen-rich environment. Double nitride uses the same treatment process as nitriding, but it results in a thicker, harder layer than nitride.

drill tap

A tool that can drill and tap a hole in a single motion. Drill taps, also known as combined drill and taps, cut down on production time by removing the need to switch tools between drilling and tapping operations.

drive square

A square extension at the top end of a tap. The drive square allows a tap to be secured in a machine’s toolholder.

drive square size

The width of one side of the tap’s drive square. Drive square size is important when selecting a toolholder for tapping operations.

extension tap

A tap with an extended shank. Extension taps, also known as pulley taps, can cut threads in holes that would otherwise be difficult to access.

form tap

A type of tap that creates threads through deformation rather than cutting or removing material. Form taps, also called fluteless taps, generally create stronger threads than traditional taps.

gas tap

A type of pipe tap used for cutting threads in pipes for hydraulic and gas systems. Gas taps, also known as NPTF taps, have 1-2 tapered threads and form highly precise threads that do not require sealant.

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.

hard chrome plating

A surface treatment method that results in a layer of hardened chromium on the metal. Hard chrome plating increases hardness and reduces surface roughness.

hardness

A material’s ability to resist indentation or scratching. An increase in hardness generally leads to an increase in brittleness and a decrease in toughness.

heat resistance

The ability to resist degradation when under extreme heat. Heat resistance is important for taps, which are exposed to high levels of friction and heat during the tapping process.

heels

The edge of a tap’s land opposite the cutting edge. Heels play an important role in reducing friction and prolonging tool life.

high-speed steel

HSS. A category of tool steels used for cutting tools. High-speed steel is an inexpensive material with high toughness.

Imperial System

A system of measurement used primarily in the United States, the United Kingdom, Myanmar, and Liberia. The Imperial System uses inches and feet to measure length.

inch tap

A tap measured using the Imperial system of measurement. Inch taps are commonly used in tapping operations, and their key measurements are listed in inches.

internal threads

A type of thread that spirals around the interior of a hole. Internal threads engage with fasteners to hold two or more components together.

International Organization for Standardization

ISO. An international organization that establishes standards and guidelines for various products and processes. ISO taps have short overall lengths and metric shank diameters.

interrupted thread tap

A tap with a cutting edge on every other thread. Interrupted thread taps are used to improve chip evacuation and allow more cutting fluid into holes.

Japanese Industrial Standard

JIS. A set of manufacturing standards used commonly in Asia. JIS taps have short overall lengths and metric shank diameters.

lands

The threaded area of a tap between the flutes. The lands are the portion of the tap that contact the workpiece to remove material.

machinability

The relative ease with which a machining operation can cut material from a workpiece. Machinability generally decreases with the hardness of the workpiece material.

machine tap

A tap used in CNC tapping operations. Machine taps have many common variations.

major diameter

The largest diameter feature on a tap’s threads. Major diameter is the diameter from crest to crest on a tap.

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 CNC machines but also less precise and efficient.

master tap

A tap with 7-10 tapered threads and additional lands. Master taps distribute cutting forces over more cutting edges than most taps, which is beneficial when tapping materials with low machinability.

mating part

An object that a workpiece has been manufactured to fit. Mating parts include screws and holes with internal threads.

metric system

A standard system of measurement used widely internationally. The metric system uses meters and millimeters to measure length.

metric tap

A tap measured using the metric system. Metric taps’ key measurements are listed in millimeters.

minimum full thread depth

The depth to which threads must be cut into a hole to accommodate the intended fastener. Minimum full thread depth is determined by the workpiece specifications and is typically at least 1.5 times the tap’s major diameter.

minor diameter

The smallest diameter feature on a tap. Minor diameter is the diameter from root to root on a tap and is typically equal to the diameter of the tap drill.

nitride

A chemical compound containing nitrogen, an inert gas. Nitrides improve the hardness of metals, including cutting tool materials.

nitriding

A surface treatment method that heats metal within a nitrogen-rich environment. Nitriding improves the hardness and abrasion-resistance of metals.

nominal size

A tap measurement that indicates the tap’s major diameter and the TPI or pitch. Nominal size is written as two numbers separated by a hyphen.

NPT tap

A tap for cutting threads into pipes. NPT taps, also known as pipe taps, form precise threads that maintain a tight seal.

NPTF tap

A type of pipe tap used for cutting threads in pipes for hydraulic and gas systems. NPTF taps, also known as gas taps, have 1-2 tapered threads and form highly precise threads that do not require sealant.

overall length

The length from one end of the tap to the other. Overall length is an important factor in deciding the correct tap for a tapping operation.

peck tapping

A tapping technique that periodically retracts the tool to clear chips or flood the hole with cutting fluid. Peck tapping is often used when tapping blind holes.

percentage of thread

The amount of a fastener threads’ surface area that engages with the internal threads of a tapped hole. The percentage of thread varies depending on characteristics such as hole depth and workpiece material.

personal protective equipment

PPE. Any clothing or device used to minimize exposure to hazards and prevent injuries. Personal protective equipment for tapping includes eye protection to guard against flying chips.

pipe tap

A tap for cutting threads into pipes. Pipe taps, also known as NPT taps, form precise threads that maintain a tight seal.

pitch

The distance between corresponding points on consecutive threads. Pitch can be determined by measuring the distance between two adjacent crests or roots.

pitch diameter

The diameter of a threaded part at the point where the size of the threads and the size of the spaces between threads is equal. Pitch diameter is larger than the minor diameter but smaller than the major diameter.

pitch diameter limits

A measurement used to describe the accuracy of threads a tap will create. Pitch diameter limits, also known as thread limits, indicate the difference between the pitch diameter of the tap and the pitch diameter of the threads that the tap will create.

plug tap

A type of tap that has 3.5 to 5 tapered threads. A plug tap, sometimes called a type B tap, is a general-purpose tap that can be used in a variety of materials and tapping operations.

powdered metal

A type of tool material created by using pressure and heat to shape and solidify metal powder. Powdered metal tools are harder and more wear-resistant than high-speed steel.

pulley tap

A tap with an extended shank. Extension taps, also known as pulley taps, can cut threads in holes that would otherwise be difficult to access.

rake angle

The angle between the front of the cutting tool and a line that passes through the thread crest and center of a tap. Rake angles affect cutting forces and contact between the tap and workpiece.

relief angle

The angle formed by the slope of the land and a line tangent to the cutting edge of a tap. The relief angle directly follows the cutting edge and reduces tool wear while increasing chip flow.

roots

The lowest point on a thread. The root size helps determine important thread measurements, such as pitch and diameter.

safety glasses

Protective eyeglasses with metal or plastic frames and impact-resistant lenses that may or may not offer vision correction. Safety glasses often have protective side shields.

sealant

A material or liquid that provides an airtight or watertight barrier. Sealants protect moving components in a fluid system from leaks and contamination.

semi-bottoming tap

A type of tap that has 2-3 tapered threads. A semi-bottoming tap, also known as a type C tap, is commonly used to cut threads in blind holes.

shank diameter

The width of a tap’s shank. The shank diameter is slightly smaller than the tap’s major diameter.

specifications

A description of the essential physical and technical properties of a finished part. Specifications outline important information including finished part dimensions and acceptable tolerance ranges.

spiral flute tap

A type of tap with helix-shaped flutes. Spiral flute taps pull chips up and out of the hole.

spiral point tap

A type of tap with straight flutes and an angled cutting face on the first few threads. Spiral point taps are only used on through holes and force chips down through the bottom of the hole.

steam oxide

A surface treatment used to reduce friction between the tap and the workpiece. Steam oxide improves cutting tool performance and lessens tool wear.

steel alloys

A kind of steel that contains intentionally added alloying elements to modify its characteristics. Steel alloys can be difficult to machine and should be tapped with a lower rake angle.

straight flute tap

A type of tap with flutes parallel to the tap’s centerline. Straight flute taps evacuate chips from either the top or bottom of a hole and are often used in hand tapping or on materials that create short chips.

strength

A material’s ability to resist forces that attempt to break or deform it. Materials with low strength may adhere to the tap’s surface without proper surface treatments.

surface treatment

A procedure that alters the properties of the surface of a material. Surface treatments have a variety of benefits, such as improved hardness and reduced friction.

tap

A cylindrical cutting tool used to produce internal threads in a preexisting hole. A tap, sometimes called a thread tap, has thread forms on its outer surface that match the internal threads it is designed to produce.

tap drill charts

A table that lists various tap sizes and their corresponding tap drill sizes. A tap drill chart serves as a reference to help operators determine appropriate tap drill sizes when drilling a hole before tapping.

tap drill size

The size of the drill required to create a specific threaded hole. Tap drill size determines the size of the hole before tapping.

taper tap

A type of tap that has 7 to 10 tapered threads. Taper taps, also called hand taps, are the first tap used when hand tapping blind holes, and they are also often used to tap through holes.

thread form

The unique shape or profile of a thread. Thread forms vary depending on the shape of their crests, roots, and flanks.

thread length

The length from the end of the tap to the highest thread. The thread length, also known as the body length, affects how efficiently a tap can cut threads into a hole.

thread limits

A measurement used to describe the accuracy of threads a tap will create. Thread limits, also known as pitch diameter limits, indicate the difference between the pitch diameter of the tap and the pitch diameter of the threads that the tap will create.

threads per inch

TPI. The number of threads along the tap within one inch. Threads per inch is used to determine the pitch on inch taps.

through holes

A hole that begins on one side of a workpiece, extends through it, and exits on another side. Through holes have openings on both sides.

titanium aluminum nitride

TiAIN. A compound of titanium, aluminum, and nitrogen used as a coating for cutting tools. Titanium aluminum nitride offers higher hardness and heat resistance than both TiN and TiCN.

titanium carbonitride

TiCN. A compound of titanium, carbon, and nitrogen often used as a coating for carbide cutting tools. Titanium carbonitride offers good abrasive wear resistance and higher hardness than TiN.

titanium nitride

TiN. A common coating element used to reduce friction on high-speed steel and carbide tools. Titanium nitride increases surface hardness, wear resistance, and insulation against heat.

tool geometry

The collective angles formed by the dimensions of a cutting tool that make a tool unique. Tool geometry is an important factor in ensuring taps create accurate internal threads.

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 factors such as using the proper tool geometry and cutting fluids.

tool wear

The erosion of tool material as a result of friction. Tool wear degrades the accuracy and precision of a tool.

toolholder

A device used to hold a cutting tool in place. Toolholders come in a variety of shapes and sizes to fit different machine tools and cutting tools.

toughness

The ability of a material to absorb energy without breaking or fracturing. Tough cutting tools can withstand sudden stresses but are less hard.

TPI

Threads per inch. The number of threads along the tap within one inch. TPI is used to determine appropriate drill and tap sizes.

type B

A type of tap that has 3.5 to 5 tapered threads. A type B tap, sometimes called a plug tap, is a general-purpose tap that can be used in a variety of materials and tapping operations.

type C

A type of tap that has 2-3 tapered threads. A type C tap, also known as a semi-bottoming tap, is commonly used to cut threads in blind holes.

type E

A type of tap with a short chamfer that has 1.5 to 2 tapered threads. A type E tap, also known as a bottoming tap, is used to cut threads near the bottom of a blind hole that has very little clearance between the bottom of the hole and the deepest required thread.

vaporizing

A surface treatment method that exposes metal to a steam furnace. Vaporizing creates oxide on a tool’s surface, which reduces friction and helps cutting fluid stick to it more effectively.

wear resistance

A material’s ability to resist the gradual wearing away caused by abrasion and friction. Increased wear resistance can lengthen the life of a tap.

workpiece

A material being machined or undergoing another type of processing. Workpieces for tapping operations are generally metals.