Spun Metal Cones & Funnels | Custom Cone Manufacturer

Why spun

One Piece of Metal, No Weld Seam

A fabricated cone is cut, rolled and welded. That leaves a longitudinal seam that has to be ground, dressed and — on stainless — pickled and re-passivated. On thin walls the weld also pulls the profile out of round, which shows up later when the cone has to mate with a ring or a duct.

Spinning forms the cone from a single blank over a conical mandrel. There is no seam, the wall thickness stays uniform around the circumference, and the profile follows the mandrel to within a couple of tenths of a millimetre. For anything that has to be airtight, concentric or visually clean, that difference is the whole argument.

No seam to leak, grind, pickle or paint over
Uniform wall thickness around the full circumference
Concentricity held to the mandrel, not to a weld fixture
Reflectors, funnels and venturi profiles formed in one pass set

What we spin

Cones, Funnels, Reducers and Venturi Profiles

Conical funnels & hoppers

Any included angle, with a rolled or flanged top edge and an optional welded or spun outlet stub.

Venturi & reducer sections

Two-angle profiles, throat sections and duct reducers formed as one piece to keep the bore concentric.

Roof vents & caps

Mushroom caps, rain caps and cowls where the profile has to shed water and still look clean.

Plain cone sections

Straight cones from Ø20 mm to 1,500 mm, thickness 0.5–6 mm, trimmed square to the axis.

Specification

Angles, Diameters and Thickness

Parameter	Range	Notes
Included angle	15°–120°	Narrower angles need more passes; below 15° we usually machine from tube
Large-end diameter	Ø20–1,500 mm	Above 1,500 mm the cone is made in halves and welded, then dressed
Wall thickness	0.5–6 mm	Aluminium 0.5–4 mm, stainless and steel 0.5–6 mm
Length	up to ~1,200 mm	Longer parts need a support spider or a two-piece build
Concentricity	0.2 mm as spun	0.05 mm on a machined bore
Edge options	rolled bead, spun flange, straight trim	Bead diameter and flange width to your drawing

If your cone has to fit an existing duct or ring, send the mating dimension and its tolerance, not just the cone. We size the mandrel to the fit, which is often a different number from the nominal cone diameter.

Connections

Flanges, Beads and Outlets

How a cone joins to the rest of the assembly decides more of the price than the cone itself. Four options cover most jobs:

Rolled bead: the edge is curled over for stiffness and a safe handling edge. Cheapest, no secondary part.
Spun integral flange: the flange is formed from the same metal — no weld, no separate ring, best for airtight joints.
Welded lap flange: a separate ring welded on. Used when the flange needs a specific thickness, bolt circle or material.
Outlet stub: a short cylindrical or threaded section, either spun integrally or welded and dressed.

Bolt holes are drilled after forming, on a jig, so the pitch circle stays concentric with the bore. Hole position tolerance of ±0.3 mm is normal; ±0.1 mm is possible on a machined flange.

Applications

Where These Parts End Up

Ventilation and HVAC: duct reducers, roof cowls, extractor hoods
Dust and bulk handling: hoppers, chutes, transition pieces
Process equipment: filling funnels, sight cones, flow straighteners
Lighting and signage: conical shades, top caps, spacers
Architecture and furniture: decorative cones, planter liners, lamp bases

In every one of these the same two properties matter: the bore is round and the wall is even. That is what spinning gives you and what fabrication struggles to match at thin gauges.

Finishing

Finishes That Survive the Application

As-spun aluminium comes with fine roller marks that read as a directional grain — often acceptable as-is for ducting and hidden parts. For visible parts we offer bright-dip anodising (clear or coloured), mirror polishing to Ra 0.4 µm, powder coating to any RAL, and wet paint. Stainless is supplied mill finish, brushed, or passivated after welding.

Tell us whether the cone is seen, touched or only functional. Finishing is usually 15–30% of the piece price, and specifying polish on a hidden hopper is money spent on nothing.

FAQ

Questions Buyers Ask Us

Can you spin a cone with an included angle under 20°?

Down to about 15°, yes, using multiple passes and a support spider to stop the nose from drifting. Below that the wall thins too much and the profile becomes unstable, so a machined cone from solid or tube is usually the better answer — we will quote whichever is cheaper rather than force the process.

Do you weld the flange or spin it?

Both, depending on the joint. A spun integral flange is seamless and best for airtight or thin-wall parts. A welded lap flange is used when the flange needs a different thickness, a specific bolt pattern or a different material. We default to spun flanges unless your drawing specifies otherwise.

What is the largest cone you can make in one piece?

Ø1,500 mm in one piece. Above that we build the cone in two halves, weld the longitudinal seams, grind and dress them, then re-check roundness. For very large duct transitions that is normal practice and the seam is invisible after finishing.

How concentric can a spun cone be?

0.2 mm between the large-end bore and the small end as spun, which covers most duct and funnel work. If the cone carries a bearing, a shaft or a machined spigot, we machine that feature after forming and hold 0.05 mm.

Can you match a cone I already have as a sample?

Yes — send the part and we reverse-engineer the profile, including any radius that a drawing would miss. We return a dimensioned PDF for your approval before cutting the mandrel, so there are no surprises at first article.

Keep reading

Batch Runs, Straight from the Baskets

A recent run of spun aluminium cones coming off the machines — racked in stillage baskets, ready for finishing and packing. Series from 500 pcs ship on a fixed schedule.

Watch on YouTube

Spun Metal Cones, Funnels & Reducers