Sheet Metal Layout and Pattern Development Flashcards

What is the 'neutral axis' in sheet metal bending?

Answer: The axis where the metal neither stretches nor compresses during bending

The neutral axis is the theoretical plane within the material thickness that neither stretches (tension) nor compresses during bending. It is used to calculate bend allowance accurately.

How is the K-factor used in sheet metal bend calculations?

Answer: To define the location of the neutral axis as a ratio of material thickness

The K-factor is the ratio of the neutral axis location to the material thickness (t). It typically ranges from 0.33 to 0.50 and is used in bend allowance calculations to determine accurate flat pattern dimensions.

What is the standard practice when transferring a pattern from a template to sheet metal?

Answer: Scribe the outline with a scratch awl or prick punch the key points

Scribing with a scratch awl or prick punching key points transfers the pattern precisely onto the sheet metal surface. This creates fine, accurate reference marks for cutting and bending.

When laying out a rectangular duct fitting, why is the inside dimension used rather than the outside dimension?

Answer: The inside dimension ensures the correct airflow area and proper fit with connecting ductwork

Sheet metal ductwork is dimensioned by inside measurements to maintain the designed cross-sectional area for proper airflow. Using inside dimensions also ensures correct fit when connecting to other duct sections.

What is a 'dog ear' in sheet metal layout?

Answer: The triangular waste piece at the corner of a pattern that must be removed before folding

A dog ear is the small triangular piece of excess material at the corner of a pattern where seam allowances or edges overlap. It must be trimmed away so corners fold cleanly.

What is the preferred method for creating a pattern for a compound curved surface that cannot be developed by standard methods?

Answer: Use approximate triangulation or segmented construction methods

Compound curved surfaces (like spheres) are non-developable and cannot be flattened without distortion. Approximate methods such as segmented construction (gores or zones) or triangulation provide workable patterns.