i got 2 tungston carbide scribers one by mail order the other from lowes.they are suppose to have the hardness of 9 on moh scale.but one scratches a gem and the other does not.could something have happened to it along the way to change the hardness and make it harder or softer.the one that scratches doesnt scratch my diamond,so its not a 10.wondering could the other one have gotten softer some how.i had the one from lowes 1st and used it more than other could that have anything to do with it.thx
-
It is certainly possible for someone or something to have screwed up in mfg such that the carbide did not form properly, did not sinter completely, contains impurities that reduce the hardness, and probably many more possibilities. It is also possible that the "sharp point" is not as sharp as it used to be so it takes greater force to create a scratch.