While I am thinking about it, I just wanted to add a bit of additional info about hammer weight and cutting power.
The mass of the hammer makes it easier to cut deeper, but it also makes it easier to break the tip off the graver. If you find the graver tips blunting often, you are hitting too hard. It is common to want to hit harder to cut faster, but this is not correct.
To cut a line faster, you tap the chisel faster........more taps per minute.
If you need to cut deeper, you can hit a little harder(and raise the chisel handle at the same time) but too deep in one pass, and the tip will break off again. How deep you can cut in one pass will depend mostly on the hardness of the material you are cutting. For example, copper can be deep cut in one pass with little trouble, but hardened blade steel will require a very light touch, and several passes to get to the same depth.
A very light hammer will give you more margin for error. Since you can't hit as hard with it, you'll be less likely to overpower the chisel point. In theory, you could cut fine with a 3 pound hammer, but your level of control would need to be somewhere between, "wizard" and "ninja" level :D
If I seem to be going on about the chisel point breaking, it's because with a broken point, you will never be able to cut a clean line. It does not take much of a chip off the point to cause trouble.....sometimes you can't even see the problem without some magnification, but if it seems like the tool was cutting great, and then all of a sudden just will not work the same, look to the tip first, it's probably chipped off.
To sum this installment up, sharp tools, light, fast taps with a light hammer, will get things done........that and a whole lot of practice.
Darcy