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BuyCone / Transition Flat-Pattern Guide
Full cone · frustum · lobster-back — print and roll correctly
How to use each of the three modes, read the derivation panel, print at 100%, and add your own seam allowance before cutting.
Open the generator
Use Full Cone, Frustum / Transition, or Lobster-Back Elbow — then print the tiled PDF at 100% and add your own seam allowance.
Open Cone / Transition Flat-Pattern Generator →Mode 1 — Full Cone
Enter base diameter and either vertical height or slant height. The tool develops a right circular cone into a circular sector: slant length L is the sector radius, and the included angle is θ = 360° × (R / L). Use vertical height when you know how tall the cone stands; use slant height when you measured along the side. Mixing them up is the most common input error — see troubleshooting.
Mode 2 — Frustum / Transition
Enter large and small end diameters plus height or slant. The pattern is an annular sector (outer arc = large circumference, inner arc = small). Top and bottom are interchangeable for the flat pattern — the labels only tell you which radius rolls to which diameter. Equal diameters degenerate to a cylinder rectangle (no cone taper).
Mode 3 — Lobster-Back Elbow
Enter pipe/duct diameter, total turn angle, number of gores (segments), and centerline bend radius. End gores are half-length (they butt to straight pipe); inner gores are full-length. Alternate gores flip when rolling. Centerline radius must stay larger than the pipe radius so the throat stays open.
Reading “Show the Math”
Open the derivation panel under Dimensions. It lists the radii, slant lengths, included angle, and arc lengths the preview uses. Use it to cross-check a shop drawing or textbook development before you commit material.
Print, Tape, and Roll
Download the full-scale PDF. Print at 100% / Actual Size — never Fit to Page. Page 1 carries a 1 in (or 50 mm) reference square; measure it with a ruler before cutting. Multi-page templates include dashed overlap/tape bands — align those edges, tape, then cut the outline. Roll the blank so the dashed seam edges meet, then add your joining allowance outside that finished edge.
No Seam Allowance Included — On Purpose
The pattern is the finished developed surface only. Lock seams, welds, riveted laps, and soldered joints need different overlaps, so the tool does not invent one. Add allowance after printing per Seam Allowance — How Much to Add for Your Joining Method.
Related Template Tools
For wrap-around pipe coping instead of cones, use the Tube Notch Template Generator and its Tube Notch Guide. For brake blanks after cutting, see the Sheet Metal Bending Guide, Bend Radius Calculator, and Sheet Metal Gauge Chart.
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Recommended Sheet Metal Layout & Cutting Tools
Cut the developed pattern, then form and join — products from the TestTalkHQ affiliate catalog
Malco M2006 10" Left Offset Snips
- Offset left-cut for long pattern edges
- Keeps hands clear of the sheet
- Shop standard for sheet-metal layout cuts
- Pairs with right-cut snips for curves
Malco AV73 Right Offset Snips
- Long-cut right offset for arcs
- Follow outer/inner sector edges
- Aviation-style compound leverage
- Complement to left-offset snips
Malco TS1 TurboShear Attachment
- Drill-powered shear for long cuts
- Faster than hand snips on large blanks
- Useful after tracing the PDF template
- 20-gauge sheet metal capacity class
Klein Tools 86528 Sheet Metal Punch Set
- Snap-lock and hole punch set
- Useful near seam edges for fasteners
- HVAC / duct fab staple
- Pairs with riveted transitions
Neiko Auto Body Hammer & Dolly Kit
- Hand-form cones and gores after cutting
- Dolly support for rolling thin sheet
- Useful for lobster-back dry-fit tweaks
- Shop fab companion to snips
Catalog gaps: No hand seamer / seamers, rivet gun, or sheet-metal brake products exist in the TestTalkHQ affiliate CSV at publish time — we do not substitute unrelated electrical or welding gear for those roles.
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