Square-to-Round vs Cone Transition — Which to Use

These Are Not Competing Tools

It is tempting to ask “which flat-pattern tool should I use?” as if one replaces the other. Wrong framing: they solve different end conditions. The Square-to-Round Transition Flat-Pattern Generator develops a rectangular (or square, or offset) base into a round. The Cone / Transition Flat-Pattern Generator develops round-to-round geometry — full cones, frustum reducers, and lobster-back elbows. You pick by opening shape, not by brand preference. Often you use both on one air path.

When to Use Square-to-Round (Triangulation)

Use the square-to-round generator when one end is rectangular and the other is round: plenum to spiral, rectangular trunk to round branch, hopper throat to round discharge, offset collar on a square box. Inputs are base W×D, diameter, height, and optional offset. Math is triangulation + sequential unfold — covered in the guide. If the blank won’t close, use troubleshooting before cutting again.

When to Use the Cone Generator

Use the cone tool for round-to-round work: a full cone, a frustum / concentric reducer between two diameters, or a lobster-back (gore) elbow. Those patterns are circular or annular sectors (or gore sets), not triangulated square lobes. Walk through modes in the Cone / Transition Flat-Pattern Guide; when a sector won’t roll true, use Cone troubleshooting.

When You Use Both on One Job

Common shop sequence: square plenum → square-to-round transition (this generator) → round trunk → concentric reducer or lobster-back elbow (cone generator) → round branch. Each fitting gets its own flat pattern from the tool that matches its ends. Nest the blanks together in the 2D Sheet Nesting Optimizer and price cuts with the Cut Cost / Time Estimator.

Decision Table

Quick Rule

If either end is rectangular (or you need a rectangular-to-round offset), open square-to-round. If both ends are round — cone, reducer, or gore elbow — open the cone generator. Don’t force a rect-to-round job into a sector pattern or a round reducer into triangulation.