Tailstock
Tailstock is the unit at the far end of a turning machine that supports the free end of the work, and it exists because a lathe has a problem that the headstock and turret cannot solve alone. The headstock grips the work at one end and turns it; the turret brings the tools to it; but work that is long and slender, held only at the chuck, overhangs unsupported. Its free end droops under its own weight, it flexes and whips as it turns, and it pushes away from the cutting tool — so a long shaft turned unsupported comes out tapered and chattered. The tailstock answers by standing at the far end of the bed and pushing a support into the work’s other end, so the part is held at both ends and turns rigidly between them. It is the quiet, sliding unit of the lathe — a casting on the bed that the machinist slides up to the work, locks, and extends — and its small movement changes a shaky long part into one that turns true. This entry sets out what a tailstock is, what it supports, and how it does its work.
The support that the far end needs
The tailstock earns its place from the physics of a long rotating part. A piece of work gripped at the chuck with a length overhanging unsupported acts like a cantilever: it bends under its own weight and under the cutting force, the bend growing towards the free end, and the free end whips as the work turns — the chatter and taper that every turner knows on long parts. Support the free end, and the part becomes a beam held at both ends instead of a cantilever: the sag is cut many times over, the work no longer whips, and the tool cuts a true diameter along the whole length. The tailstock provides exactly that second support, and its position on the bed is set to the work: the machinist slides the whole tailstock along the bed to the length of the part, clamps it, and then extends its centre into the end of the work. Whether the part is a long shaft between centres or a shorter part being drilled from the end, the tailstock is the unit that lets a turning machine do what its chuck alone cannot.
The tailstock and its centres
The working end of the tailstock is a centre: a pointed cone of hardened steel that seats in a matching hole in the end of the work and locates it exactly on the machine’s axis. Two forms matter. The dead centre is a solid cone that turns with the work — the work rotates on the point, which must be greased and which suits slower work, because the friction of the work spinning on the fixed point heats and wears it. The live centre — the rotating centre — carries the cone in a bearing, so the point itself rotates with the work and there is no rubbing at the point; it runs fast and cool, and it is the centre of nearly all modern tailstock work. Work that is turned between centres is held between the headstock centre and the tailstock centre, driven by a carrier plate rather than gripped in a chuck — the classic way to turn a long shaft true, because the part is located by its own centres and can be turned, removed and re-set without losing its axis. The centre is mounted in the tailstock’s quill or ram, a sliding sleeve that the handwheel or a hydraulic cylinder extends and retracts, with its own locking to hold it at the set depth.
More than a support
The tailstock is not only a prop for long work — it is also the lathe’s second working end, and its quill is built to carry tools as well as centres. The quill’s nose carries a taper, so it can hold not just a centre but a drill or a reamer: the tailstock is slid up to the work, the quill fed forward, and the drill advances into the rotating part to drill a centre hole or a full bore from the end. On the manual lathe this is the standard way to drill — the tailstock brought up, the drill held in its chuck, the handwheel feeding the quill. Because the tailstock sits on the bed’s centre line, whatever it carries — centre, drill, reamer — is presented exactly on the axis of rotation, so the holes it drills are true to the turned diameters the same axis produces. The tailstock thus doubles as the machine’s end-working station, supporting the part and machining it, both on the true centre.
The tailstock on the CNC machine
On the modern turning centre, the tailstock has joined the automation this wiki describes. Its slide along the bed is commanded by program or set by a servo, its clamp engages automatically, and its quill extends by hydraulic pressure at a set force — so the machine brings the tailstock up to a long part, supports it, and retracts it, all within the cycle, without the operator. The pressure of the quill is set and controlled, because a tailstock must support without pushing the work off centre or marking it: enough force to hold the part rigid, not so much that it springs the slender work or burns the centre. On long parts the CNC lathe manages the whole dance — the tailstock supporting the free end while the turret turns the diameters, then retracting when the operation moves to the far end, the program orchestrating every move. It is the same support the manual turner gave by hand, now delivered automatically, which is what lets the turning centre run long, slender parts part after part with the tailstock always in the right place.
The tailstock’s quiet place
The tailstock is easy to overlook because its work is so simple — it slides, it locks, it pushes a centre into the work — yet it is one of the parts that decides what a lathe can turn. Without it the turning machine is a machine for short, stiff parts held at the chuck; with it the same machine turns long shafts, turns work between centres to a true axis, and drills and reams true holes from the end. Every long part that this wiki’s turning work describes — the shaft, the spindle, the pin, the slender component — depends on the tailstock being slid to the right place, locked rigidly to the bed, and offering its centre truly on the axis. It pairs with the headstock and turret as the third unit of the lathe, and alongside the other elements of the machine it completes the anatomy of the turning machine — the unit at the far end that holds the other end of the work, so that the long, true, chatter-free part is not the skill of a lucky turner but the ordinary, repeatable output of the machine.