I found this guy on youtube (Nick Saporito) that has many videos on how to design different shapes, Icons, items, and signs that may help understand how to do many things with Inkscape.
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT