Sheet Metal Cone Flat Pattern Calculator
SI
Imp
Imperial
Inputs
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Large diameter
(D1)
Large finished diameter of the frustum.
in
Small diameter
(D2)
Small finished diameter. Use 0 for a full cone.
in
Vertical height
(H)
Straight vertical height, not slant height.
in
Seam allowance
Straight seam allowance added as a simple slant-height strip for area estimating.
in
Results
Default result
Edit inputs
Pattern sector angle
(theta)
103.45
°
Pass
Also computed
Outer pattern radius
(R1)
Pass
20.881
in
Inner pattern radius
(R2)
10.44
in
Slant height
(s)
10.44
in
Large arc length
37.699
in
Small arc length
18.85
in
Pattern area
295.19
in²
Blank area with seam
300.41
in²
Adds seam allowance as seam width times slant height.
Diameter difference
6
in
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Method notes
3 notes
Slant height s = sqrt(H^2 + ((D1 - D2)/2)^2). Pattern radii are s*D1/(D1-D2) and s*D2/(D1-D2).
Sector angle comes from matching the developed outer arc to the finished large circumference: theta = 180*D1/R1 degrees.
This is a geometric flat-pattern screen. Thickness compensation, bend/stretch allowance, forming method, locks, hems, notch relief, grain direction and shop tooling are not included.
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