Understanding the anatomy of human hands makes it way more easy to draw them.
I am always starting with a rectangle as the basis (pic 1) and adding the different parts of the fingers as thin ellipses (pic 2).
http://www.newslinq.com/skarp-laser-razor/
Interesting use of color to frame the hammer.
Use of tone to communicate the surfaces of the drill handle.
Nice use of white pencil to add highlights but I think the dark outline blends too much into the cast shadow and background.
Quick motion study with simple lines and shapes.
I like how the color was added quickly and evenly over the whole watch and then the form was delineated with shadows and highlights.