How is a pin-gauge measurement carried out?
1.1 igus carries out a pin-gauge test, also called a “go/no-go test”, in order to ensure that our bearings meet the specifications and function properly once installed.
First of all, the bearings are press-fitted in a test housing. It must be ensured that the bearings are undamaged when they are fitted. A housing chamfer is recommended – ideally 25 to 30 degrees. The use of an arbor press with a flat punch is also recommended in order to press-fit the bearing in the housing. This is the most efficient method of installation. It also ensures that the integrity of the bearing is preserved. If you use a hammer, for example, the bearing can jam when it is being installed.
1.2 igus recommends that an arbor press be used to press-fit a plain bearing.
The actual pin-gauge test takes place after the bearing has been fitted. A “go” means that the pin falls through the bearing under its own weight, whereas a “no-go” means that the pin does not fall through the bearing, i.e. becomes stuck. As a rule, the pin gauges are graduated in increments of 0.01 mm so that it is possible to very precisely determine the dimension above which the respective pin becomes stuck. _x000D_
A pin-gauge test is the most accurate quality check because the pin behaves like a shaft in a real -world application and mirrors the smallest cross section of the bearing. It is exactly this aspect that is usually critical for the application. Pin-gauge tests are especially suitable for plastic bearings because the irrelevant “points of unevenness” of the bearing caused by the injection moulding process are not taken into account. Once the bearing has been put to use, an ideal sliding surface is achieved during the running-in phase, in which the points of unevenness of the bearing and shaft are smoothed out.
Other tests can be used to carry out a quality check on a bearing but problems can arise if these methods are applied to plastic bearings. In particular, the use of calipers should be avoided. Calipers should only be used for quick quality checks, depending on the level of accuracy desired. Depending on the pressure exerted by the caliper at the measuring point, the measurement can be falsified. For this reason, a pin-gauge test is much more reliable.
The described test can also be carried out directly on a series-produced component, depending on its accessibility (in other words, not in a test housing specially made for this purpose).