The hardness of compression molded products cannot be uniformly evaluated because of a wide variety of molded products, but in most cases, the hardness seems to be evaluated either by crushing strength or crushing force. In this study, we focused on compression molded products with low hardness. We will examine both the crushing strength and crushing force for this product and provide knowledge about the appropriate testing method.

To reduce errors in rebound hardness due to mass effects, the eNM3A10small ball rebound hardness test method and a testing machine has been developed. In this test method, an alumina ceramic ball indenter with a diameter of3mm is used alone to impact a specimen at a velocity of V1＝10m／s.

The rebound velocity V2of the indenter from the specimen is measured to obtain the coefficient of restitution e＝V2／V1, which is then taken as the hardness value of the specimen.

We have developed a new tester, eNM1A10, with an alumina ceramic ball with a diameter of1mm,which is1／3of the ball of eNM3A10, in order to reduce the minimum thickness of the sample.

The eNM1A10tester was then tested on the hardness standard blocks of e＝0.63and0.86(≒300HV and700HV)so on , and the test results were in good agreement with those of the eNM3A10，confirming the success of the prototype development of eNM1A10.