With etching and engraving, they are both the methods used to cut the lines into the hard surface, like metal. Engraving is the physical process which uses sharp tool to cut the lines straight into the surface. Etching is the chemical process where the etcher burns the lines into the surface using the acid. Here is the difference between engraving and etching.
Use in Printing
Both etching and engraving are forms of the intaglio printing that is defined by cutting the lines into the flat surface. Even though the method that produce these lines is actually different, printing process is alike. The plate is being inked and then wiped clean, leaving the ink in etched or the engraved lines only. This plate is pressed against the paper sheet to transfer inked image. If the line is deeper, more ink will hold and the prints will be darker. Etching and engraving are both print in the reverse, therefore, the artist is supposed to draw an image in a reverse when he or she is working using these media.
The line quality
Since engraving creates very hard and thin line, the engraved prints have sharp details and crisp edges which many other printing methods cannot achieve. Because of this, engraving is the best method to print currency. When you come to etching, it inclines to produce the fuzzier line, which happens as the acid burns sideways under a wax, creating the rougher and wider line than an artist originally drew. Likewise, since the artist does not have to apply much force on the etching plate, etching incline to have more fluid, softer line closer to the freehand drawing.
The process
Both of them are the method used to cut the lines on the tough surface. The major difference is that etching is being considered as the chemical process, while the engraving is the physical process. The etcher burns the lines in the surface of the material using the acid. In contrast, the engraver use the sharp, pointed tools to cut the lines straight to a hard surface.
Nature
Etching is an art of producing the image using the acid that removes metal, while engraving is the printmaking method where the artist uses pointed and sharp tool to cut the lines into the metal surface.
The physical effort needed
Etching require lesser physical effort because etcher draws a design in the wax. In contrast, engraving need more physical effort because the tool is used to cut in the metal.