308A Sheet Metal Layout and Pattern Development 2 — Questions and Answers
Question 1: How is the true length of a line determined when it appears foreshortened in a plan view?
- By doubling the plan view length
- By constructing a true length diagram using the plan view length and the height difference (Correct answer)
- By measuring the line in the elevation view only
- By dividing the plan view length by two
Correct 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.
Question 2: What is the inside bend allowance primarily dependent on?
- The colour of the metal
- The bend radius and the material thickness (Correct answer)
- The length of the piece only
- The type of sealant used
Correct 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.
Question 3: When laying out a pattern for an oblique cylinder (cylinder cut at an angle), what must be determined for each element line?
- The weight per linear foot
- The true length of each element by measuring from the base to the angled cut line (Correct answer)
- The temperature rating
- The paint colour
Correct 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.
Question 4: What tool is commonly used to scribe arcs and circles on sheet metal during layout?
- A ball-peen hammer
- Trammel points or dividers (Correct answer)
- A rivet gun
- A plasma cutter
Correct 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.
Question 5: In pattern development, what does the term 'girth line' refer to?
- The maximum weight a fitting can support
- The line representing the perimeter or circumference of a fitting at a given cross-section (Correct answer)
- The cutting speed of a shear
- The welding path around a joint
Correct 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.
Question 6: What is a 'cheek' in sheet metal pattern development?
- A type of rivet
- A triangular or flat side piece of a fitting such as a transition (Correct answer)
- A measurement error
- A type of solder joint
Correct 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.
308A Sheet Metal Layout and Pattern Development 2
How is the true length of a line determined when it appears foreshortened in a plan view?