CNC Lathe | Tool Offset and Tool Length Offset

Tool Offset Introduction

Tool offset is to compensate for the difference between the actual tool used and the imagined part. Tool offset or tool length offset is the offset of the turret zero with respect to tool tip.

Turret zero is the intersection point of turret axis and turret front face.

A tool is mounted on turret. The distance between the turret zero and the tool tip along X axis is XT, and that along Z-axis, is ZT.

Tool Offset Memory Location

Tool length offsets are entered into tool offset memory locations. There are 16/32 tool offset memory locations. Tool offsets are identified by the code XX AFTER TOOL NUMBER. Tool offsets are numbered from 1 to 32. Tool offsets for each tool are entered into separate tool offset memory locations. Established tool length data of a particular tool can be entered into any of the 32 tool offset memory locations.

To bring in the established tool offset values of a called tool, the corresponding offset number is to be programmed following the tool number.

Consider that for tool 1, the offset values are entered in tool offset memory location 1 ; Then, N50 T01 01 ; is programmed.

Tool number indicates the turret station number where the tool is mounted, and the tool lengths of which are to be entered.

Tool type indicates tool location code or tool identification code.
Of X indicates X offset length of tool.
Of Z indicates Z offset length of tool.
Dia / radius indicates tip radius of tool.
Wear 1 indicates tool wear along X-axis.
Wear 2 indicates tool wear along Z-axis.
Radial wear indicates radial wear.


Tool number 5
X offset 180
Z offset 7
Data is to be entered into tool offset NO10.
Following data is entered into no. 10.

= 50-25
= 25

Cursor moves down, line by line when “ENTER” key is pressed.

When ever the tool is called to a particular position, CNC takes into account, zero offset, tool length offset, distance of the target position from work zero, and the position where the tool is located and then calculates the distance to be traveled in each axis.

The position of tool tip with respect to turret zero is different for each tool. Tool offsets are used to establish, the offsets of each tool tip with respect to machine zero.

Assume that the machine reference point is X600:ZX500 ?

The tool is brought close to the component, and a cut is taken on OD. The diameter is measured. The corresponding display position in the X-axis is noted down. Assume that diameter measured is 50mm and the corresponding display position is X400.

Similarly a cut is taken on the face. The corresponding display position in Z-axis is noted down. The slide is taken back to a safe position and brought forward so that the turret face is touched on to component face. Corresponding display position in Z-axis is noted down.

The difference in the positions displayed corresponding to tool stationed at work zero and to that at the reference position is made use of to establish the tool length offsets.

Note: When the slides are positioned at the machine reference point, turret zero itself is considered as the machine reference point.

The established data is entered into any one of the tool offset memory locations.

Tool Identification Code

Tool type is the tool identification code used for the purpose of application of tool nose radius compensation. There are nine types of tool identification codes from 1 to 9. The following diagram shows different location codes. Based on the position of tip centre with respect to leading tip the above codes are assigned.