What sort of protractor did you acquire from Amazon? Does it have a brand name? (Amazon will sell anything to anyone.) These days, you can purchase a very accurate digital stylus force gauge (SFG) for a few bucks more than the cost of the Shure device, which is laughably inexact by comparison, even though for much of our audio lives that is all we had to use. I recommend the Ortofon digital SFG, because the weigh pan is completely non-magnetic. Some of the others that you can buy on eBay and elsewhere have a slightly magnetic pan. Not good if you are setting VTF for an MC cartridge, which tend to have powerful magnets.
If right now you only have a Shure SFG, I do not mean to imply you shouldn't use it. It does require care and skill and a willingness to fuss, in order to get the VTF in the ballpark, which is to say +/-0.3gm.
If right now you only have a Shure SFG, I do not mean to imply you shouldn't use it. It does require care and skill and a willingness to fuss, in order to get the VTF in the ballpark, which is to say +/-0.3gm.