This symbol represents whether or not the insert has a chip breaker. It also refers to whether the insert has a hole or not. A negative insert can have one-sided or double-sided chip breaker.

The symbol that represents the tolerance class is determined by a combination of three tolerances; the nose height (m), inscribed circle (d) and thickness (s). To produce close tolerance inserts, grinding is necessary.

This is the symbol that represents the clearance angle of an insert. An insert with 0° clearance angle, which is shown by symbol N, is called a negative insert. An insert with a clearance angle other than 0° is called a positive insert. Many turning inserts have clearance angles shown by symbols P, C and N.

This symbol represents the direction in which the insert can machine. If the insert can be used for both left and right (thus neutral) then the symbol is generally omitted.

For the inch coding method, the diameter of an inscribed circle is shown by a numerical symbol. For example, an inscribed circle of  3/8 inch (9.525mm) is represented by the symbol 3. An inscribed circle of 4/8 inch (12.70mm) is shown as 4.

Extra care is needed with handling these drills as they are very delicate, especially sizes from 0.1mm - 0.4mm. Make sure everything is running true without any lateral movement.

There are a number of different types of honing, for example "round" honing and "chamfer" honing. The type of honing employed is shown by the appropriate symbol. Cutting tool manufacturers amploy their own honing geometries (size and angle) according to insert grade and size. Generally the honing symbol is omitted from an identification code.

This symbol represents the direction in which the insert can machine. If the insert can be used for both left and right (thus neutral) then the symbol is generally omitted.

Cemented carbide, coated carbide, cermet, ceramic and other hard material inserts have the cutting edge honed so as to prevent fracturing in the machining.

This is the symbol that represents the clearance angle of an insert. An insert with 0° clearance angle, which is shown by symbol N, is called a negative insert. An insert with a clearance angle other than 0° is called a positive insert. Many turning inserts have clearance angles shown by symbols P, C and N.

There are a number of different types of honing, for example "round" honing and "chamfer" honing. The type of honing employed is shown by the appropriate symbol. Cutting tool manufacturers amploy their own honing geometries (size and angle) according to insert grade and size. Generally the honing symbol is omitted from an identification code.

Chip breakers play an important role in chip control. Cutting tool manufacturers employ their own breaker geometries and as such the symbol is optional.

Read on for further information, including cutting lengths, spindle speeds, feed rates, and chip loads for drill bit sizes.

A solid carbide twist drill is perfect for delicate drilling through hard materials for model engineering, archaeology and scientific laboratory work.

For turning operations, mainly G-class (sometimes J-class) or M-class inserts are used. Inserts with tolerance classes other than G, J and M are mostly used on face milling cutters.

This symbol represents the actual thickness of the insert. It works on the same principle as that of the inscribed circle.

For turning operations, mainly G-class (sometimes J-class) or M-class inserts are used. Inserts with tolerance classes other than G, J and M are mostly used on face milling cutters.

The symbol that represents the tolerance class is determined by a combination of three tolerances; the nose height (m), inscribed circle (d) and thickness (s). To produce close tolerance inserts, grinding is necessary.

This symbol represents the actual thickness of the insert. It works on the same principle as that of the inscribed circle.

This represents the corner radius (nose radius) of an insert. It is standardized in intervals, for example after 0.4mm with intervals of 0.4mm, and after 4.0mm in intervals of 0.8mm.

However, for the metric coding, the diameter of an inscribed circle is represented by the cutting edge length using a two-digit number. Therefore, even if the inscribed circle is the same, the symbol for the cutting edge will vary.

For the inch coding method, the diameter of an inscribed circle is shown by a numerical symbol. For example, an inscribed circle of  3/8 inch (9.525mm) is represented by the symbol 3. An inscribed circle of 4/8 inch (12.70mm) is shown as 4.

However, for the metric coding, the diameter of an inscribed circle is represented by the cutting edge length using a two-digit number. Therefore, even if the inscribed circle is the same , the symbol for the cutting edge will vary.

The insert geometry is represented using letters of the alphabet. A wide range of geometries are listed as standard for example; triangle, square, round, polygon and rhombus.

The insert geometry is represented using letters of the alphabet. A wide range of geometries are listed as standard for example; triangle, square, round, polygon and rhombus.

Chip breakers play an important role in chip control. Cutting tool manufacturers employ their own breaker geometries and as such the symbol is optional.

Ideal for drilling through PCB, and printed circuit boards. Made of fibreglass, printed circuit boards require a tough micro drill, and our tungsten carbide drills range will outperform similar HSS drill bits.

This represents the corner radius (nose radius) of an insert. It is standardized in intervals, for example after 0.4mm with intervals of 0.4mm, and after 4.0mm in intervals of 0.8mm.

Cemented carbide, coated carbide, cermet, ceramic and other hard material inserts have the cutting edge honed so as to prevent fracturing in the machining.

Look at the different drill bit sizes of carbide micro drills to determine their effective cutting length, spindle speed, feed rate and chip load.

Most horologists find the easiest way to use these micro drill bits is by first finding the centre with a graver and then holding a micro drill in a pin-vice and then taking them to the work. Use very light pressure whilst taking the drill in and out periodically. No lubrication is necessary, although a small dab of oil can help.

This symbol represents whether or not the insert has a chip breaker. It also refers to whether the insert has a hole or not. A negative insert can have one-sided or double-sided chip breaker.

These hard, solid tungsten carbide micro twist drill bits, versatile in their application,  are excellent for producing smooth, precision holes and drilling through all hard metals. Ensure a steady hand when using these micro drill bits, ideally used at high speed in a pillar drill.