Basic Turning



Half stock removal and/or depth of cut (in terms of radius)

When turning, the thickness of material to be removed is referred to as the depth of cut (ap). However there are cases when the depth of cut in radius terms is used. If this case the divide the depth of cut by two to gain depth of cut in radius terms.



This refers to the direction that the tool machines in. For turning, face the insert of the tool holder or boring bar. If it machines right, it is a right-hand tool holder or boring bar. If it machines left, it is a left-hand tool holder or boring bar.  For face milling cutters, see the cutter head-on. If the cutter rotates counterclockwise, it is a right-hand cutter. If it rotates clockwise, it is a left-hand cutter.


Heavy metal

A metal that has a high density. Generally 4~5 times that of iron and copper.



A machining process that spirals down as it cuts into the workpiece.



Hafnium carbide



Hafnium nitride


High-efficiency machining

High-efficiency machining is a term that is used to express machining that is carried out that employs high feed rates and/or high cutting speeds.


High heat hardness

A property that refers to the ability of a tool grade that means even under high cutting edge temperature conditions the tool grade maintains its hardness.


High relief angle cutting edge geometry

Is a term used to refer to a cutting edge that has a large flank angle. This is to reduce problems such as welding that are common when machining aluminium alloys.





Analysis of time, work, processes and efficiency.


Index head

A device that can be either manually or automatically operated to index the workpiece to the correct position to carry out machining.


Indexable tool holder

A tool holder that uses indexable inserts for the cutting edge.



A term used to describe a method of machining in which a cutting tool moves from the outer diameter to the centre of the workpiece when facing.




High-speed steel

A material made from tungsten, molybdenum, cobalt, vanadium and other elements, to withstand high temperatures, friction and impact. Used for making tools that can machine metals at high speeds.


High-speed steel drill

A drill that is made of high-speed steel.


High-speed steel reamer

A reamer that is made of high-speed steel.



Hobbing (gear machining) is a machining process that uses hobs to generate gears in a workpiece. Hobs are used on gear cutting machines.


Hot forming

A term used to express the forming of a metal at temperatures higher than the recrystallization temperature.


Hot hydrostatic press

A press that incorporates a heater and uses an inert gas as a medium to apply the pressure.



Rockwell hardness unit on C scale.



A hyper-eutectoid steel is a steel with more than 0.80% C.



A hyper-eutectoid steel is a steel with more than 0.80% C.



Hypo-eutectic describes the area before the eutectic point. A point at which 2 or more different crystals precipitate in to one.



A hypo-eutectoid steel is a steel with less than

0.80% C.











A term used to refer to an indexable cutting edge.



Used to prevent electricity from being conducted.


Interrupted machining

Interrupted machining refers to machining in which the cutting edge comes into and out of contact with the workpiece. This is mainly associated with face milling and/or end milling machining. However interrupted machining can be encountered when turning is conducted.



International Organization for




International tolerances.