How much should I tighten the head of my razor?
Be sure that you have not mistakenly assembled the razor with the bottom piece upside down, which is easy to do with a three-piece safety razor like the Merkur 23C long handle. When you secure the blade in the cutting head, it should leave a gap between the edge of the blade and the bottom half of the head assembly. This small gap is what allows the blade to cut the hair while the guard glides along your skin. You should tighten your safety razor until the threads stop, without leaving it loose and without overtightening, which could damage the screw and possibly break it.