Replacing forging or casting plus turning with drawn and ironed near-net parts

Forging and casting both produce a shape that is close to the finished part but not close enough: the functional surfaces still have to be machined, and the machining removes the allowance that the process needed. Where the part is a thin-walled cylindrical housing or sleeve, drawing and ironing can deliver the same near-net result without a forge or a foundry.

What each route leaves for the machinist

Route	Near-net on the outside?	Near-net on the bore?	Remaining operations
Casting + machining	Approximately, with draft angles and riser allowance	No - the bore is usually cored undersize and bored	Bore, functional faces, sometimes the outside; porosity risk
Forging + machining	Approximately, with forging allowance	No - the bore is punched or drilled undersize and turned	Bore, outside, faces; the allowance becomes chips
Cold extrusion + machining	Close, especially on axisymmetric parts	Often close, but usually still turned for tolerance or finish	Bore and/or outside depending on tolerance
Deep drawing + ironing	Yes - the die sets it	Yes - the punch sets it	Only the features forming cannot make: threads, cross holes, sealing faces

Why the wrought route is usually better for a thin wall

No porosity. A casting can hide porosity that only appears after machining or in service. Drawing and ironing start from wrought strip, so the wall is fully dense by construction.
No draft angle. A casting or forging needs draft so it can leave the mould or the die. An ironed wall is straight and parallel, which is what a sliding fit or a press fit needs.
No allowance to remove. Forging and casting allowances exist to be machined away. An ironed wall is already at its finished thickness, so there is nothing to remove and no chip to produce.
Grain flow in the right direction. Forming deforms the material along the wall rather than cutting across it, which improves strength and wear behaviour in a pressure or sliding application.
Thinner walls are practical. A cast or forged wall has to be thick enough for the process and for the machining allowance. A drawn and ironed wall is limited by the drawing, not by the mould.

Where forging or casting still wins

Solid or very thick sections. Ironing thins a wall; it does not make a solid part.
Complex external geometry. Ribs, bosses and non-axisymmetric features are easier to cast or forge than to form.
Very large parts. Balford draws up to Ø250 mm with a maximum blank of 600 mm and a maximum drawn height of 200 mm; parts beyond that belong to a heavy process.
Low volume. A drawn and ironed part needs tooling. In small quantities, casting or forging from an existing pattern can be cheaper.

Frequently asked questions

Can ironing replace a casting?

Where the part is a cylindrical or near-cylindrical housing or sleeve with a thin to medium wall, yes. The drawn and ironed part is wrought rather than cast, so there is no porosity, no draft angle on the wall, and no allowance that has to be machined away. Parts with ribs, bosses or thick solid sections are still better cast or forged.

Can ironing replace a forging?

For thin-walled cylindrical parts, yes. A forged part carries an allowance that is turned away; an ironed part arrives at its finished wall thickness. The forging route still wins for solid parts, for very large parts, and for complex external geometry.

Does a drawn and ironed part need any machining?

It needs machining only for the features forming cannot produce - threads, cross holes, sealing faces, or a bore held tighter than the forming process can guarantee. The wall, the bore and the outside diameter are formed.

What is the size limit for this route at Balford?

Up to Ø250 mm deep draw diameter on presses up to 350 t, with a maximum blank of 600 mm and a maximum drawn height of 200 mm. Beyond that the part belongs to a heavier process, and we will say so at quoting.

Discuss Your Project

Send the drawing, we will tell you whether ironing removes a machining step

Send the drawing with material, both diameters and the tolerances that matter. Balford reviews the forming route, the ironing passes and the tooling before quoting.

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