Layout is a term used to define the process of placing part feature markings onto the surface of the stock the part will be made from. Children’s activity books often have projects that involve cutting out shapes following lines printed on paper. Those lines are like the layout (or outline) of the part you are to create. For the machinist, the part stock is usually metal, and the tools used to create the layout lines are varied, each designed for a particular purpose. The process of layout falls under a category of work referred to as benchwork. Benchwork is a semi-precise method of machining performed using hand tools and a bench vise to hold the stock. Benchwork skills are important for the fabricator who is repairing a part or making a prototype where extensive machining processes are not reasonable. Sometimes, machining processes require a significant time investment to set up and program sophisticated equipment. Benchwork can be a more efficient option in some cases.

Let’s revisit the dart board analogy used in an earlier chapter to understand when benchwork might be preferrable. A dart board is a good example of precision and tolerance.  Consider the bull’s eye. A dart must land in the area that defines the bull’s eye zone. It may be a little left, right, high, or low within the zone and still count as a bull’s eye. This is similar to machining in that the zone is like a part dimension, and the size of this zone is the tolerance. As long as the dart lands in the zone, the goal is achieved.

For the machinist, we usually have small tolerance zones that must be maintained; however, there are instances where the tolerance zone is larger and more forgiving. In these instances, if we apply all the principles used to maintain tight tolerance, time and energy would be wasted. This is where semi-precise methods may be used, and we typically refer to those methods as benchwork. Semi-precise is a term used to explain a lower level of detail in manufacturing processes.

Tools used to perform benchwork operations are rulers, protractors, dividers, trammels, squares, and straight edges. A straight edge performs a similar function as a ruler when creating a straight line, but a straight edgeis a precision ground tool that has a more accurate edge than a ruler. Most of the tools used in benchwork have been superseded due to the decreasing cost of more complex measuring and layout equipment, but using equipment that needs no batteries and is of simple design has value for benchwork tasks.

Attributions

1. Figure 5.1: Cross line layout for feature location by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0
2. Figure 5.2: Darts by Richard Matthews is released under CC BY 2.0
3. Figure 5.3: SImple measuring tools by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0