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Absolute Tool Length for CNC Machinists

Absolute Tool Length is an industry standard feature in CNC machining that provides continuity across machine brands and controls.

What is Absolute Tool Length?

Absolute Tool Length is a method of tool measurement that can be utilized by any number of machine tools, whether it is a Hurco or one of the other brands that offer this level of flexibility to their customers. When using Absolute Tool Length calibration, the length of a particular tool is measured against the same standard as all other tools. The length is calculated from the spindle gage-line to the tip of the tool. Since the spindle gage-line is an industry standard reference, this form of tool calibration allows the tool length to become machine independent, allowing the freedom to move these tools between different machines without recalibration.

Spindle Gage Line

Measuring Tool Length

The tools can be measured in the machine by using an offline tool pre-setter. The pre-measured tool length can also be entered manually into the tool setup data from information contained on a setup tag that was attached to the tool after it had been measured.

Contrary to popular belief, the spindle gage-line isn’t the spindle nose itself. It is actually a measured diameter that falls along the spindle or toolholder taper. For CAT 40 tooling, the magic diameter measurement is 1.750”; it's 2.750” for CAT 50 holders.

Companies such as Renishaw sell a tool known as a “Master Length Reference Tool,” which is a precision tool used in the calibration of tool probes. It's used for measuring 5-axis centerlines, as well as other uses where a precise known length is needed. The precise length value is stenciled on the side of the body of the tool. However, by using the reference diameter data from the section above, a makeshift master length tool can be created using a tool holder, a gauge pin, and an optical comparator. If you clamp the gauge pin in the holder and find the reference diameter along the tool taper using the comparator, you can then measure the reference length to the tip of the pin – essentially creating an accurate known length tool.

Absolute Tool Length image

Absolute Tool Length and Hurco 

In the past, when conforming to industry standard protocols, Hurco has been just a little different from other machine tool manufacturers, especially in the areas of part and tool setup. However, that has changed over the years. With each new release of the WinMax® control software, Hurco engineers build in new features that allow the user to configure control settings and parameters to best suit their needs, make them more efficient, and ultimately closer align with the industry standard.

One of these features was the introduction of Absolute Tool Length, which not only helped Hurco better conform to the industry standards that shops are used to, but also opened the door for WinMax software enhancements that would otherwise have been impossible, such as using standard G54-G59 work offsets with conversational programs, part and tool probing enhancements, NC/Conversational Merge capabilities, simplified part setups, and Hurco’s advanced Universal Rotary feature for multi-axis programming.


Click the link for more detailed information on the application of Absolute Tool Length with your Hurco machine.

To see for yourself, download the FREE 90-day WinMax® desktop trial

You'll find more helpful resources, such as training videos and webinars, at Hurco Connect.


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