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Shape and surface roughness measurements of screws / Surface roughness measurement using a laser microscope


Screws are used to join parts by fitting tightly. A tight fit is created by static friction, and manufacturers need to ensure that the screws have enough friction to prevent them from becoming loose. The amount of static friction is proportional to the screw’s surface roughness. Consequently, manufacturers must measure surface roughness to ensure the screws conform to standards. In precision screws, the area that needs to be measured is so small that it is difficult to measure using conventional evaluation methods. In addition, to determine the friction values, the surface roughness needs to be measured instead of conventional line roughness.

Olympus' solution

Olympus' OLS4100 3D laser microscope enables you to evaluate three-dimensional shapes such as the threads or grooves of a screw, the pitch or height of the threads, and the angle of the flank. The OLS4100 also makes it simple to measure the roughness of a precision screw’s contact surface so manufacturers can ensure quality. The microscope’s stitching function seamlessly combines multiple images into a single image for wide-field observation.

Entire 3D image of a precision screw 

3d image of a precision screw

10X objective lens; 1x zoom; stitching       

Surface roughness of the root of a thread

surface roughness of the root of a thread

100X objective lens; 1x zoom

Olympus IMS

Products used for this application


With the Olympus LEXT OLS5000 laser scanning confocal microscope, noncontact, nondestructive 3D observations and measurements are easy to produce. Simply by pushing the Start button, users can measure fine shapes at the submicron level. Ease of use is combined with leading-edge features to deliver an acquisition speed four times faster than our previous model. For customers with larger samples, LEXT long working distance objectives and an extended frame option allow the system to accommodate samples as large as 210 mm.
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