30 deg
40 deg
50 deg
ANGLES
As the angle gets bigger, the edge gets finer. This means
that unless the metal gets harder, the edge becomes more
delicate and can be more easily nicked and worn. The
harder the metal is, the more expensive the shear will be.

From the TOOLS page the #1 shear is being used on dry or
coarse hair free hair so the edge needs to be stronger to
reduce wear and  "rougher" so the hair doesn't slide out.

For the #2 shear the edge still needs some strength but
since you will be using this shear on hair you are holding
between your fingers so it can't move, it can be a finer
smoother edge so you get less stress on your hands.

The #3 shear will be used in ways that don't necessarily
require the shear to be closed to cut but most of the time the
hair is still being held so the blade needs to be very fine and
very smooth so it slices the hair razor like as it moves past it.

If you have big hands then you may be able to use one
shear for both #2 and #4.

If you plan to pass up the good money men will pay if you
can do a good mustache trim then you may also be able to
have one shear for #1 and #2.

The #2 shear can be specialty sharpened so it will do slide,
slice, and slither cutting but if you plan to do that you need
to buy a shear with the hardness of a #3 shear.