Sheet Metal Layout and Pattern Development Flashcards

How is the true length of a line determined when it appears foreshortened in a plan view?

Answer: By constructing a true length diagram using the plan view length and the height difference

A true length diagram is constructed by plotting the plan view length horizontally and the height difference vertically, then measuring the hypotenuse to obtain the true length.

What is the inside bend allowance primarily dependent on?

Answer: The bend radius and the material thickness

Bend allowance is calculated based on the bend radius and material thickness. A larger radius or thicker material requires more allowance for the material that stretches along the neutral axis during bending.

When laying out a pattern for an oblique cylinder (cylinder cut at an angle), what must be determined for each element line?

Answer: The true length of each element by measuring from the base to the angled cut line

Each element line on an oblique cylinder has a different length due to the angled cut. The true length of each must be individually measured or calculated to create an accurate flat pattern.

What tool is commonly used to scribe arcs and circles on sheet metal during layout?

Answer: Trammel points or dividers

Trammel points (beam compass) and dividers are the standard layout tools for scribing arcs and circles on sheet metal. Trammel points can handle larger radii than standard dividers.

In pattern development, what does the term 'girth line' refer to?

Answer: The line representing the perimeter or circumference of a fitting at a given cross-section

The girth line represents the total perimeter measurement around a cross-section of a fitting. It is laid out as a straight line in the flat pattern and divided into equal segments.

What is a 'cheek' in sheet metal pattern development?

Answer: A triangular or flat side piece of a fitting such as a transition

A cheek is a flat triangular or trapezoidal side piece of a transition or offset fitting. Cheeks are developed separately and then joined to the curved or angled sections of the fitting.