Original sentence: Being cautious, I place the cutter flat on the sharpening surface of the stone and give the cutter a slight clockwise turn.For purposes of cleaning, I often remove the heads and carefully, maintain head/blade integrity because interchanging them can cause problems.I have not used other kinds of sharpening stones, only the flat diamond stone available in many places.I my own case, I have done this at least a half-dozen times and am very satisfied with the results.If your heads are dull and you deem them ready for replacement, the worst that can happen is that your ineptness (if present) make it absolutely necessary to purchase new cutter assemblies.It began to make sense to me, that if one kept the angle the same, the sharp point angle of the blade could be sharpened on a flat stone.My experience is solely with this particular head.Since you want to remove only ten-thousandths of an inch and are intending only to re-establish the fine edge of the cutter baldes, minimal pressure and movement is suggested.Specifically, I refer to the HQ55+ shaver head.The physics of this effort do not permit sharpening of the decidedly important, second shaving blade mechanism, the "Super Lift & Cut technology".This is a sensible suggestion to lengthen the life of your razor's sharpness.Though not mentioned elsewhere that I have found and certainly, Philips Norelco™ does not recommend trying to sharpen the blades on this razor, I made the discovery that the primary element, first-contact blades can be repeatedly sharpened.To clean them well of the curly hairs from the neck which often accumulate, I disassemble head and blade and use running water and a brush to clean the blade assembly and then the head, carefully lying the pieces on a clean terry towel to dry before reassembly