What Drives the Cost of a Split Bearing Housing?

A split bearing housing can be priced from the drawing once the batch, the bore callout and the inspection list are fixed, and the 420 g of aluminum is the smallest line in that price. The rest sits in gravity casting, bolted boring, T6 stress relief and first-article checks.

The part is an A356-T6 housing, the AlSi7Mg alloy listed as GB/T 1173 ZL101A, 120×95×70 mm with a Ø60 H8 bore, all design targets. Ten steps carry it from melt to final inspection, and the route decides what a quotation has to cover.

What drives the cost of a split bearing housing?

A split bearing housing is priced by its route, not its poured weight. A steel mold that runs one or two parts per cycle, pending foundry sign-off, carries a tooling share paid back across the batch.

Melting, degassing, pouring, gate cutting and blasting each add a station the part passes once. A 5–8 mm wall slows solidification at the half-round seat, so the pour and the feed design carry more of that line than the metal price does. T6 then adds a solution treatment, a water quench and an aging cycle, with two furnace loads behind it.

Why does the second boring setup cost more than the first?

Two setups sit behind the Ø60 H8 bore, and the second one carries the assembly. The split faces are milled flat to 0.05 mm, then the halves are bolted and bored as one body. Bolting adds a torque station, a boring pass on the paired halves and an unbolting step after the bore is checked.

Because the bore is checked in the bolted state, the CMM reading is taken on the bolted pair, the state the shaft will see, and a recheck follows every setup change. A quote that prices one boring operation has priced the flat face alone; the paired cut, torque and recheck separate the two setups.

Where does the 5–8 mm wall show up in the price?

The 5–8 mm wall reaches the price through feeding and pour time. The half-round seat sits on the heaviest section, so the riser must hold metal there after the thin end has frozen. Pouring at 700–740 °C into a mold preheated to 250–350 °C, both typical ranges pending foundry sign-off, leaves a narrow window.

A shrink cavity over Ø1 mm scraps the housing after boring, and that scrap is charged to the casting step rather than the machine shop. Adding wall thickness without adding feed enlarges the cavity and lengthens the cycle, so the saving expected from extra metal does not appear.

Why is blasting quoted before machining?

Shot blasting is quoted as its own operation because it runs before the split faces are milled and before the bore is cut. Cast surfaces reach Sa 2.5 under ISO 8501-1, and the machined bore and split faces are not blasted afterwards.

That order keeps blasting media out of the bore and off the faces that carry the fit. Reverse it and the bore and split faces need masking or rework, a manual step that lands in the price. A quote that folds blasting into a finish line has hidden that step.

What else belongs beside the piece price?

Four inputs belong beside the piece price: batch size, alloy and temper, the inspection list and the tooling basis. A first article runs PT on the machined seat, a CMM check on coaxiality and perpendicularity, a three-point micrometer check on the bore and a go/no-go trial on the 4×Ø9 holes. Each check has a station and a report.

Batch size sets how the steel mold is amortised, and the drawing sets how many checks repeat on every lot. An RFQ that carries the drawing, the batch and the inspection list lets the quotation price the route the floor will run.

Send the drawing with the split line, the Ø60 H8 callout and the inspection list marked, plus the batch size, so the four lines can be priced against one route.