Names of each part of a tap

Hand taps

Kinds of screw thread specifications

Kinds of thread shapes

Standard and others

Names of the part of a tap


The portion following the thread portion. Shank is the portion which the chuck and holder grasp when they holInformationp.

Push hole

The hole against which the tightening bolt strikes to fasten a die to its holder.

Chip hole

The hole where chips are stocked or are ejected.


A tap has cutting edges to cut threads. The chamfer is the cutting edges where the top of threads are ground off in an inclined manner. The inclination angle is called the chamfer angle.


A part following the shank is prepared in a square. When a tap is used by attached to machines, the square prevents the tap from turning.

Cutting angle

At the face vertical to the axis, the cutting angle is the angle at which the cutting face of OD’s cutting edge crosses with its radial line.

Cutting face

Cutting face is flute face following chamfer and plays the role of main cutting. Chips run on this face.


Put on adjustable dies, slit is used to minutely adjust the screw threads.

Adjusting screw

A screw used to adjust the slit to adjust the screw threads.

Thread portion

Common name for the threaded portion. Thread portion is very important in specifying the accuracy of internal screw threads.


Relief is a relieved face prepared to avoid unnecessary contact to finished face. When the relief consists of plural faces, from the face near the cutting edges, they are called the first relief and the second relief respectively.

Relief angle

The inclination angle of relief face against the finished face.


The portion between thread portion and shank being applied by manufacturing reason or by using reason.


The portion connecting relief face with flutes.

Heel angle

At the face vertical to the axis, heel angle is the angle between a central line crossing heel anInformationngent line of chip hole face crossing the heel.


Distance between the top of thread and that of next thread

V groove

shape of a slit. Screw size is adjusted by either bolts or wedge.


Face connecting thread top with thread bottom. At cross section including the axis line, frank is generally straight.


Portion connecting with the cutting edge on land, and not having relief.

Flute portion

Flutes applied to eject chips. Depending on tap sizes and application, the number of the flutes will be 2 to 4.

Pitch diameter

Diameter of the imaginary cylinder or cone where the width of thread groove and that of thread become equal.


Portion having the shape like bank between the cutting edge and heel.

Land width

Width of the portion having the shape like bank between the cutting edge and heel.

Hand taps

Bottoming tap

Last tap to be used in the last tapping process to cut the threads all the way to the hole end. Named No.3 tap as well.

Taper tap

A tap having the inclination toward the tap end. Named No. 1 tap as well.

Plug tap

A tap cutting threads to the middle of hole. Named No. 2 tap as well.

Kinds of thread specification

Whitworth thread

stated in inch or pitch. Pitch is the number of threads per 1 inch. Thread angle is 55 degree.

Pipe thread

Screw threads used for the connection of pipes, pipe parts, parts for fluid and others. There are parallel threads and taper threads. In taper threads, usually, taper is 1/16.

Metric threads

Each part of the threads is designated in millimeter. Most widely used for fastening machine parts. Thread angle is 60 degree.

Unified threads

Pitch is the number of threads per 1 inch or 25.4mm. Thread angle is 60 degree.

Kinds of the shape of thread portion

Single thread and multiple threads

Single thread- lead is equal to pitch. Multiple thread- lead is equal to the integral number more than 2.

Right hand thread and left hand thread

Seeing in axis direction, when the screw leaves off in clock wise turn, it is the right hand screw. And when it leaves off in un-clock wise turns, it is the left hand screw.

Standard and others

ISO Standard

Having various kinds of threads, ISO is the international standard integrating the different thread standards of various nations.

JIS Standard

A national standard built on Industrial Standardizing Law to improve the standardization in Japan. Japanese industrial standard.

Cutting oil

Heat is produced during cutting process. And we flow such special oil having quenching effects during the cutting process. Cutting oil has the effect of fire protection by avoiding spark dispersion.

Class of tap

Tap class is classified into 3, precision, middle and rough. The thread class of most suitable tap for the required internal screw thread is specified.