How to choose the right saw blade

Blade Size Chart

Choose the blade that best suits the thickness of the material being cut (or sawn). The ideal ratio is 2.5 to 3 teeth on the materials at any time. I have added a MM size comparison to this. Use a B and S gauge to determine the thickness if you need to. Now I would also caution against listening too close to others when they say you MUST use a particular size blade on certain gauges of metal. Depending on your job, and your personal taste, you may use a different blade size than others.
As long as you have at least 2.5 to 3 teeth on the metal, you can use what ever blade you would like.
Also. Remember to use some sort of blade lubricant!

Jeweler Saw bade chart
Blade Size For use with: Blade Thickness Blade Depth Teeth per Inch Drill Size for Piercing
6/0 24 gauge .0070'' .0140'' 76.0 79
5/0 22-24 gauge .0080'' .0157'' 71.0 78
4/0 22 gauge .0086'' .0175'' 66.0 77
3/0 22 gauge .0095'' .0190'' 61.0 76
2/0 20-22 gauge .0103'' .0204'' 56.0 75
1/0 18-22 gauge .0110'' .0220'' 53.5 73
1 18-20 gauge .0120'' .0240'' 51.0 71
2 16-18 gauge .0134'' .0276'' 43.0 70
3 12-14 gauge .0140'' .0290'' 40.5 68
4 10 gauge .0150'' .0307'' 38.0 67
5 8 gauge .0158'' .0331'' 35.5 65
6 6-8 gauge .0173'' .0370'' 33.0 58