Cone / Frustum Configurator

Axial height by default — the vertical distance between the large and small ends, measured along the centreline. If your drawing gives the slant height, the side slope or the apex angle instead, change "Height given as" and enter that; the axial height is worked out and shown first in the results.

They are three ways of stating one angle. The side slope is measured from horizontal — from the plane of the large end. The wall angle is measured from the vertical centreline, so it is 90° minus the side slope. The apex angle is the full angle at the tip, between opposite walls: twice the wall angle. A cone with 60° sides has a 30° wall angle and a 60° apex angle; a cone with 45° sides has a 90° apex angle. The results show all three, so you can check against whichever your drawing uses.

Because the slant height is then exactly twice the difference in radii (cos 60° = 1/2), and the developed angle is 360° × the difference in radii ÷ the slant height = 180°. Steeper sides give a narrower sector, flatter sides a wider one; at 30° sides it is already about 312°.

It can. With the dimension basis on "Mid-surface", your diameters are developed exactly as entered and thickness is ignored. Choose "Inside face" or "Outside face" and the pattern is developed on the neutral layer instead, offset by (thickness / 2) × cos(wall angle) — which is what you want when your diameters were measured on a finished face, at the corner of a plate edge cut square to the plate. (Measured level in the plane of the end, the shift would be (thickness / 2) ÷ cos(wall angle) instead.) K is 0.50 in both cases.

It is where your diameters were measured from. Inside face means the bore of the finished cone; outside face means the outer skin; mid-surface means you have already worked to the middle of the material. The finished part is the same either way — only the flat blank changes, because the neutral layer sits half a thickness away from whichever face you measured.

Set the small diameter to 0. On the mid-surface basis the pattern becomes a plain sector closing at the apex instead of an annular sector; on the inside-face basis the neutral layer still has a small radius there, so a small inner arc remains. Note that a full cone cannot use the outside-face basis: there is no material at the apex to offset from.

Split the pattern into identical segments: each keeps both radii and takes an equal share of the angle. The cone-in-segments tool (/tools/cone-segments-calculator) gives the count that fits your plate, one segment as DXF, and the chord for marking it out by hand.

The cut outline does not change at all — it is identical for both, and you can verify that in the DXF. Press brake adds bend marks on the BEND layer at each facet line, plus the bend angle, facet chord and out-of-round figures, because a brake bump-forms the cone as flat facets rather than rolling it smoothly.

There is no single right answer, which is why the tool reports the consequences instead of choosing for you: more facets give a rounder cone and more hits. Watch the facet chord and out-of-round figures at the large end and pick what your part tolerance allows.

As a constant-width strip along one radial edge only. The original edge is written to the BEND layer and the new outside edge to CUT. It is a simple lap allowance, not a shop-specific seam design — check it against your own standard.

Whichever unit you have selected. The file records it in the $INSUNITS header variable (4 for millimetres, 1 for inches), so CAD software that reads that variable will place it at the right scale.