The Square or Rectangle to Round Transition Template makes four panels for a centered, zero-thickness paper model. It preserves a specified triangulated mesh, with its lap strips and printing limits visible. A downloaded pattern is the start of the paper check.
1. Measure one geometry datum
Width and depth belong to the same rectangular base plane. Height is the perpendicular distance to the centered nominal round end. Use the same inside, outside or other selected measurement datum consistently; this tool performs no thickness or neutral-surface conversion. Diameter is limited to the smaller base edge. Offsets and end flanges are outside this model.
2. Develop true lengths, not plan lengths
BCcampus Pattern Development constructs flat triangles from true lengths. The US Navy Steelworker, Volume 2, printed pages 2-19 to 2-20, independently describes triangular development and treats a warped-surface development as an estimate. A plan-view distance combined with the perpendicular rise gives a true side. The app retains 13 triangles per panel and checks their developed edges against spatial lengths.
Our four corner seams and 48 straight chords are explicit product choices. They differ from the textbook seam arrangement and flexible final curve; neither source validates this whole app or a physical fit.
3. Keep the four labels and seam map
F, R, B and L run counterclockwise viewed from above. Join F-right to R-left, R-right to B-left, B-right to L-left and L-right to F-left. Opposite panels match for centered geometry. Rectangle width panels generally differ from depth panels. Two distinct shapes still require four identified cut pieces.
4. Read the declared round-end approximation
The nominal circle passes through 48 vertices. Its developed edge uses 48 chords, which have a shorter perimeter and a circle-to-chord inset. The report prints nominal circumference, faceted perimeter, shortfall and maximum inset. The approximately 0.07138 percent circumference shortfall describes this chosen mesh; it is not a fabrication tolerance or a promise of smooth mating fit.
5. Use paper tabs, then record trimming
Each local right seam gets one square-ended rectangular strip of the entered width. Zero omits the strip. The reported paper area includes all four untrimmed tabs and excludes metal thickness, hems, nesting losses and later trimming. After paper assembly trim portions below the neighboring base or beyond its end while keeping both bare design edges. Do not treat this allowance as a locked seam, Pittsburgh seam or bend deduction.
6. Keep one canonical input record
The same geometry keeps its record ID across inch/mm and Letter/A4 changes. The ID uses canonical committed millimeters, the fixed subdivision count and method revision. Full canonical inputs remain in the PDF and CSV. The ID groups pieces; it is neither a secret nor an independent precision proof. NIST specifies the international inch as exactly 25.4 mm. Display fractions are approximate; geometry and tile counts never use rounded labels.
7. Print and measure both axes
Choose Letter or A4 portrait. Each panel gets its own tiled grid with 10 mm overlap and 5 mm padding around the tabbed bounds. Pattern pages carry panel, row/column, record ID, inputs and scale instructions. Summaries and browser previews are not to scale.
Use Actual Size/100%. Do not Fit/Shrink or apply a second Poster operation: these pages are already tiled. Adobe documents scale, overlap and cut marks for assembled prints. Check both 50 mm rulers on every tile. If either axis is wrong, correct printer settings and reprint; never alter design inputs to compensate.
8. Make the physical acceptance record
No measured print-and-assemble test or photograph sequence has been completed for this app. The owner acceptance step is to print F03 and F12 on Letter and A4, record PDF hash, printer/driver, actual-size setting, operator and date, then photograph the rulers in the same plane.
Align three separated crosses at every tile join. Measure base and seam across joins, cut and fold the paper, tape the stated seam order, photograph tab-end trimming, and measure base width/depth, perpendicular height and diameter across opposite vertices. A second person should confirm labels and scale instructions without opening the app. Record deviations and whether assembly closes without forcing. Tape flexibility does not establish metal fit.
9. Keep fabrication decisions separate
The paper pattern does not settle material thickness, measurement-datum conversion, metal seams, end allowances, bend deduction, smoothness, airflow, pressure or structural performance. The Sheet Metal Weight Calculator, Bend Deduction Calculator, Duct Sizing Calculator and Pipe Miter Template address separate tasks. Their outputs do not certify this pattern.