A grinding support for polishing diamond needles or pickup devices having a sharp trailing edge, intended for use with information carriers, comprises a grinding groove having the desired cross-sectional profile of the needle and having small diamond grains embedded and party projecting from the plastics of its surface. The embedded diamond grains are in a single layer in the surface and the greatest dimensions of the majority of the grains exceeds the permissible radius of curvature at the trailing edge of the needle to be produced; this maximum dimension however does not exceed twenty times this radius. Pref., the single layer of diamond grains is pressed into the thermoplastics while it is in the plastic condition, leaving a portion of the grains projecting. The average grain size is pref. is not 0.5 mu. Pref. dimensions are: max. grain size for majority of grains is 8 mu for a radius of curvature of the trailing edge of the needle of 0.5 mu. The radius of curvature (R) of the groove of the grinding plate is 0.5-2 mu. It is found that by the use of larger grains than those hitherto conventionally employed, a sharp trailing edge can be produced on the needle ground by means of the grinding plate, without this needle edge breaking away. Considerably increased grinding speeds are possible. The grinding edge and support pref. is in the form of a PVC disc with spiral grooves.
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