Is the thread long enough?

Alongside diameter, pitch and flank angle, the usable length is one of the most important parameters of a thread: If the thread is too short, the component cannot be screwed together tightly enough and could come loose during operation, leading to failure. Traditionally, the usable length of the thread is checked using gages. This is not only time-consuming, but also expensive, as a suitable gage is required for each type of thread. "With the optical shaft and cylinder coordinate measuring machines from Mahr, this measuring task for external threads can be solved easily and in just a few seconds," says Jakob Schlie, Application Engineer at metrology specialist Mahr in Göttingen.

Optically automated instead of manual
Depending on the application, the component is either clamped between centers or in a three-jaw chuck. The optical measuring process then captures the outer contour of the component in just a few seconds using the transmitted light method.

If the measurement is taken in only one rotational position, the profile at the start and end of the thread varies from measurement to measurement. This makes automatic evaluation much more difficult and is often a reason for fluctuating measurement results.

This is also a challenge when measuring the chamfer at the start of the thread: depending on the rotational position of the thread, the chamfer appears longer or shorter in a single cut.

Evaluate in seconds with MarWin EasyShaft
These challenges can be solved quickly, easily and reproducibly with the "MarWin EasyShaft" software. MarWin EasyShaft is the measuring, control and evaluation system from Mahr that is used, for example, in the optical shaft measuring device MarShaft SCOPE plus or the cylinder coordinate measuring machine PLQ. The software offers standard-compliant measurement of diameters, lengths, contour features, shapes and position tolerances with high precision as well as many new options for evaluation and documentation with clear, easy-to-use operation. MarWin EasyShaft works completely under Windows.
MarWin EasyShaft enables image acquisition not only in a section or rotational position of the component: If required, the component can even be rotated 360° during the measurement and a large number of images can be captured.

The software then derives and evaluates the summed external and internal profile from these measurements. The process is therefore independent of a specific measuring position and delivers fast and reproducible results.

Using a cylinder AOI ("Area-Of-Interest"), the images are automatically recorded in several rotational positions. The inner or outer profile can then be determined from the images using the "Extract linear profile" function. "The necessary elements and intersections can now be calculated as usual on this derived profile and the usable thread length can be determined from this," summarizes Schlie.
It is also possible to measure the chamfer length and chamfer angle in this way, for example. In addition, MarWin EasyShaft also offers the option of determining thread parameters such as external, flank and core diameters as well as the pitch and flank angle.

This enables functionally relevant measurement of threads with relatively few program steps and in the shortest possible measuring time.

Your contact for further information

Do you need detailed information about the diverse measurement and evaluation strategies from industrial practice with Mahr measuring devices? Take advantage of our Level 2 application technology training courses!
Do you have any questions? Then please contact Timo Dankenbrink, Head of Application Technology at Mahr, on +49 (551) 7073-99499 or email to  timo.dankenbrink@mahr.com.