A hollow camshaft is not machined from a solid forging. It is a steel tube with the cams pressed, shrink-fitted or formed onto it, which cuts weight and rotating inertia and leaves a bore that can carry oil. We supply the tube – cold drawn seamless or DOM – to the outside diameter, straightness and wall concentricity that your cam fitting process needs.
Price: quoted per specification. Steel prices move with the raw material market, so every quotation is confirmed at the time of order.
Why a tube instead of a solid blank
Three things drive the choice. Weight and inertia: a hollow shaft spins up faster and loads the bearings less, which matters most on high-revving engines. Cost: a tube arrives close to size, so the machining that removes metal from a solid blank largely disappears. Oil: the bore becomes an internal oil path to the cam journals, so no external line has to be routed along the head.
A solid forging still wins where the lobe loads are very high or the shaft carries a distributor drive, which is why both designs exist. If your drawing is a forging, the part is not a tube assembly and we are not the right supplier for it.
What the tube has to deliver
| Property | Why the cam assembly cares |
|---|---|
| Outside diameter tolerance | Sets the interference in a press or shrink fit, which is what carries the cam torque |
| Roundness | Uneven interference distorts the lobe position and shows up as runout after assembly |
| Straightness | Runout at the journals, and how much grinding allowance is left on the lobes |
| Wall concentricity | Balance, and a usable wall for the oil passage |
| Residual stress | Straightness that drifts after machining or heat treatment, long after the tube was accepted |
| Bore condition | Oil feed to the journals; scale or drawing marks end up in the oil |
The order of importance is not the same for every customer. A camshaft built by shrink fitting lives or dies on OD tolerance and roundness; one that is hydroformed onto the tube cares more about wall uniformity and elongation.
Grades we run
| Grade | Nearest foreign designation | Character and use |
|---|---|---|
| E355 | S355 / St52 / 16Mn (Q345, now Q355) | Weldable and tough; the common choice for tube-based camshafts |
| 1045 | C45 / S45C / AISI 1045 / GOST 45 | Higher carbon and hardenable; used where the lobes are induction hardened |
Solid forged camshafts are usually made in micro-alloyed grades such as 38MnVS6. That is a forging grade and we do not supply it. Grade names are close but never interchangeable without checking chemistry, condition and test regime, so a Chinese grade on the drawing and an EN name in your customer’s specification should be confirmed in writing before the order.
What to specify in the order
| Item | What to write | If left out |
|---|---|---|
| Size | Outside diameter × wall, both with tolerance | The fit that carries the cams is not controlled |
| Grade | E355 or 1045, with the standard you will cite | Certificate may not match the customer’s drawing |
| Condition | +SR stress relieved, or +N normalised | Straightness moves after machining |
| Straightness | Deviation per metre, and total over the cut length | Runout at the journals after assembly |
| Cut length and ends | Fixed length, square cut, deburred or chamfered | Extra machining and scrap at your end |
| Bore | Clean and free of scale; Ra if oil feeds through | Debris reaches the cam journals |
What we supply, and what we do not
We supply the tube to the drawing: drawn, cut, stress relieved, inspected and certified. We do not press or shrink the cams, grind the lobes, harden, balance or assemble the shaft. Those steps belong to the camshaft maker, and quoting them separately is the honest way to price the job – if a supplier offers you a finished camshaft and a tube price in the same breath, ask which one the certificate covers.
Testing and packing
Chemistry per heat, tensile and elongation per lot, dimensions, wall and straightness by inspection, with visual check of the bore. Tubes are oiled, end-capped and bundled with padded strapping because the outside diameter is usually a fitted surface. Certificates to EN 10204 3.1 record the heat number and the measured values, so your incoming inspection can tie the bundle to the document.