Calculator Form
Example Data Table
| Case | Large Diameter | Small Diameter | Height | Slant Height | Sector Angle | Use |
|---|---|---|---|---|---|---|
| Reducer | 600 mm | 300 mm | 500 mm | 522.02 mm | 103.45 degrees | Duct transition |
| Full Cone | 400 mm | 0 mm | 600 mm | 632.46 mm | 113.84 degrees | Funnel or guard |
| Shallow Hopper | 900 mm | 500 mm | 350 mm | 403.11 mm | 160.70 degrees | Hopper section |
Formula Used
Neutral diameter from outside diameter: Dn = Do - 2 × (1 - K) × t
Neutral diameter from inside diameter: Dn = Di + 2 × K × t
Slant height: L = √(H² + ((Dlarge - Dsmall) / 2)²)
Outer pattern radius: Rlarge = L × Dlarge / (Dlarge - Dsmall)
Inner pattern radius: Rsmall = L × Dsmall / (Dlarge - Dsmall)
Sector angle: Angle = 180 × Dlarge / Rlarge
Sector area: A = 0.5 × angle in radians × (Router² - Rinner²)
Weight: Weight = area in m² × thickness in m × density × quantity
How to Use This Calculator
Enter the bottom diameter, top diameter, vertical height, and sheet thickness. Use zero as the top diameter for a full cone. Choose whether your diameters are outside, inside, or centerline values. Add the neutral axis factor, seam allowance, edge allowance, density, and quantity. Press Calculate to view the pattern dimensions above the form. Use the CSV or PDF buttons to save the result.
Sheet Metal Cone Layout Guide
Overview
A sheet metal cone starts as a flat sector. The sector is cut, rolled, and joined. A correct blank saves time, material, and rework. This calculator supports full cones and frustums. It also handles small hoppers, duct reducers, guards, funnels, and transition pieces.
Why the layout matters
Cone work depends on the neutral diameter. The outside face stretches less than the inside face compresses. The neutral line sits between them. For common shop work, a middle value is practical. For tight accuracy, enter thickness, diameter basis, and a neutral axis factor. The tool then adjusts diameters before it builds the pattern.
What the outputs mean
The slant height is the true side length. It becomes the radial width of the developed pattern. The large and small pattern radii are measured from the theoretical cone apex. The sector angle controls the included layout angle. Arc lengths show the developed circumferences. Added edge allowance changes trim length. Added seam allowance gives extra sheet along one side for welding, riveting, folding, or locking.
Using the result in the shop
Mark the apex point first. Swing the outer radius with a trammel. Swing the inner radius when the top diameter is greater than zero. Set the sector angle from one radial line. Add the seam strip on one side. Check the large and small arc lengths before cutting. Roll the blank slowly. Bring both edges together without forcing the sheet.
Practical notes
Thick sheets may need a different neutral factor. Stainless steel can spring back more than mild steel. Galvanized sheet may need protected cut edges. Very small cones are harder to roll accurately. Large cones may need segmented blanks. Always confirm the final pattern with a test piece when tolerances are strict.
Planning checks
Review stock width, grain direction, handling space, and safe lifting. Confirm whether diameters are inside, outside, or centerline values. Record units on the drawing. Keep one revision number for every issued blank.
Benefits
The calculator gives a repeatable method for planning cone blanks. It combines geometry, material weight, seam allowance, and edge allowance in one place. It also exports results for job cards, estimates, and workshop records. This supports cleaner quoting, cutting, forming, inspection, and repeat production runs.
FAQs
1. What is a sheet metal cone blank?
It is the flat pattern used to form a cone or frustum. The blank is usually a circular sector or annular sector.
2. Can this calculator handle a full cone?
Yes. Enter the top diameter as zero. The tool will calculate a full cone sector with no inner pattern radius.
3. What is the neutral axis factor?
It estimates where the sheet bends through its thickness. A value of 0.5 places it at the middle of the sheet.
4. Should I use inside or outside diameters?
Use the basis shown on your drawing. If your drawing gives finished outside sizes, choose outside. If it gives bore sizes, choose inside.
5. What does seam allowance do?
It adds extra material along one side of the pattern. This extra strip supports welding, riveting, folding, or locking seams.
6. What does edge allowance do?
It adds trim material around the large and small circular edges. This helps during forming, trimming, or fitting.
7. Why is material density needed?
Density converts the blank area and thickness into weight. Mild steel often uses about 7850 kg per cubic meter.
8. Are the results ready for final production?
They are suitable for planning and layout. For strict tolerance work, verify with shop standards and a test blank.