Lesson 1: Drafting Equipment – Tools And Materials
Overlays
An overlay is any sheet that is placed over the original drawing. The information placed on the overlay becomes part of the interpretation of the original drawing. There are two types of overlays
Temporary overlays are made by drawing on transparent material such as acetate, tracing cloth or vellum. Overlays are used in the design process to add to or change features of the original drawing without marking the drawing. Overlays are also used to add to drawing features that would normally complicate the original drawing. Lines that would become hidden and many other details can be made clear by preparing this information on an overlay.
Permanent overlays which adhere to the surface of the drawing save much drawing time. Attaching a preprinted symbol or fixture by this method is considerably faster than drawing even if a template is used. In addition to fixture and symbol overlays, continuous material symbols are also used. These are self adhering and can be cut to any desired size or shape.
Participants