This Technical Report presents an evaluation of a round-robin test of vibration measurement methods for determining vibration in hand-held grinders. The aim of the round-robin test was to establish a test method that could meet the requirement of ISO20643 for measurement of vibration emissions in three directions, for accordance with the planned-to-be-revised ISO8662-4. The value obtained by such a test method must correspond to the highest vibration values likely to occur under typical and normal working conditions of the machine, i.e. the upper quartile of the vibration in real use. This acknowledges that the upper boundary of “typical and normal?? conditions can be exceeded by some conditions of “real use??. Vibration at grinding can mainly be divided into vibration caused by unbalance of the grinding wheel and process vibration generated by the contact between the grinding wheel and the work piece. The unbalance part has been shown to be the greater of the two and ISO8662-4 is based on this. In this Technical Report, the test method consists of a number of averaged measurements using an unbalance disc, with an unbalance corresponding to the upper limit of the unbalances found among real grinding wheels. Whereas ISO8662-4 covers all types of hand-held grinders, the round-robin test presented in this Technical Report was based on grinding with depressed centre-wheels, one of the most common grinding applications. The types of grinder used in the round-robin test are given in Table1. Table1 Grinder types and sizes used in test Type of grinder Wheel size 125mm
(5\'\') 230mm
(9\'\') Pneumatic Without auto-balancing unit With auto-balancing unit Electric With auto-balancing unit Without auto-balancing unit Two tests of the grinders were made: one using an unbalance disc and the other by real grinding. The unbalance disc test was made with a disc of new design, with the shape of a depressed centre wheel. One reference disc was sent together with the grinding machines, while the other was locally manufactured by the measuring lab. Grinding was made on mild steel with locally purchased grinding wheels. Detailed test instructions were distributed to the participants before the start of the round-robin test.