TOEIC Link Vocabulary Cluster — Tailshaft Survey: The Report Lexicon for the Shaft That Carries the Propeller and the Clearances That Say It Is Still Safe to Turn

The tailshaft is the last section of the propulsion shafting, the piece that runs out through the stern of the ship and carries the propeller in the water. It turns inside a bearing that is lubricated by oil or, in older ships, by the sea itself, and it is the one part of the shafting a surveyor cannot see running — it is submerged, loaded, and constantly worn. That is what makes the survey conceptually unusual: it is a survey of a wearing clearance, not a fixed dimension. The question is never simply is the shaft intact but how much has the bearing worn, and is what remains still within the limit the class rules allow. Every finding is written against a measured weardown and a permitted maximum. Because the survey is so procedural and so measurement-driven, it recurs as a source domain for TOEIC Link marine survey reading passages. The workflow is fixed: the shaft is examined or withdrawn, the weardown is gauged, the shaft is checked for cracks at its highly stressed points, the seals are renewed, and the clearances are confirmed within limits. That sequence generates a stable cluster of roughly forty terms. A candidate who owns the cluster reads the passage at native speed; a candidate who does not stalls on the load-bearing nouns and loses the passage's argument.

This guide isolates the cluster, groups it by survey stage, and maps each term to its native collocation and register tier, because TOEIC Link scores writing as well as reading. Pair it with the writing vocabulary precision and collocation discipline guide for the skill of choosing the exact term, and with the steering gear survey rudder and hydraulic actuator cluster, whose sterngear and clearance vocabulary overlaps directly with this survey.

Why this cluster rewards study

A tailshaft passage assumes its vocabulary the way a draft-survey or hatch-cover passage does. If a reader decodes weardown, poker gauge, and sterntube one word at a time, the attention the module intends for the inferential questions is consumed by decoding. Learning the cluster converts those stalls to zero and frees the reader to answer what the passage actually asks — why a shaft with no visible defect was still condemned, what the weardown was measured against, and where in the permitted-clearance argument the disputed finding lies.

Stage 1 — The shaft and the bearing it turns in

The survey opens with the two parts whose relationship the whole inspection measures.

Tailshaft — the aftermost length of shafting, carrying the propeller through the stern; also called the propeller shaft. Collocation: the tailshaft is drawn (withdrawn) for survey; the tailshaft is surveyed in place.
Sterntube — the tube through the stern of the ship through which the tailshaft passes, housing the bearing. Collocation: the shaft runs in the sterntube; the sterntube is flooded or oil-filled.
Sterntube bearing — the bearing, typically white metal or a synthetic material, that supports the tailshaft inside the sterntube. Collocation: the bearing is worn down; the bearing is renewed.
Bush — the sleeve forming the bearing surface, often the aft bush that carries the propeller-end load. Collocation: the aft bush is measured; the bush is re-metalled.
Liner — the sleeve fitted over the shaft where it passes through the bearing, protecting the shaft from wear and corrosion. Collocation: the liner is cracked; the liner is machined.

Stage 2 — Measuring the weardown

The heart of the survey is the wear measurement, because it is the number the class limit is written against.

Weardown — the amount the shaft has settled in the bearing as the bearing material wears; the survey's central measurement. Collocation: weardown is gauged; weardown exceeds the limit.
Poker gauge — the instrument passed down through a fitting to measure the gap above the shaft and so the weardown. Collocation: weardown is read on the poker gauge; the poker gauge is inserted.
Clearance — the measured gap between shaft and bearing; the general term the limit constrains. Collocation: clearance is within limits; clearance is built up when new.
Wear-down limit — the maximum weardown the class rules permit before the bearing must be renewed. Collocation: the reading is referred to the limit; the shaft is condemned at the limit.
Original clearance — the as-fitted clearance recorded when the bearing was new, the baseline weardown is measured from. Collocation: weardown is the difference from original clearance.

Stage 3 — Examining the shaft for cracks

Where the shaft is drawn, it is examined at its most highly stressed points, because a fatigue crack there is a fracture waiting to happen.

Taper — the tapered end of the shaft on which the propeller is fitted; a classic crack initiation site. Collocation: the taper is crack-tested; a crack initiates at the taper.
Keyway — the slot cut in the shaft for the key that drives the propeller; a stress raiser where cracks begin. Collocation: the keyway is examined; a crack runs from the keyway.
Fillet — the rounded transition at the forward end of the taper, another point of stress concentration. Collocation: the fillet is inspected; the fillet radius is confirmed.
Crack detection — the non-destructive examination (dye penetrant or magnetic particle) applied to the shaft. Collocation: crack detection is carried out; the shaft passes crack detection.
Keyless fitting — a propeller fitting without a key, relying on interference alone, which removes the keyway crack site. Collocation: the propeller is keyless-fitted; keyless fitting extends the survey interval.

Stage 4 — The seals and the confirmed condition

The survey closes with the oil seals and the statement that the shaft may keep turning.

Oil seal — the seal at each end of an oil-lubricated sterntube that keeps oil in and water out. Collocation: the seal is renewed; the seal is leaking off.
Lip seal — the flexible sealing ring that bears on the liner; the common oil-seal type. Collocation: the lip seal is replaced; the lip rides on the liner.
Oil sample — the lubricating oil drawn and analyzed for water and bearing metal as evidence of condition. Collocation: an oil sample is analyzed; the sample shows water ingress.
Continuous survey — the survey scheme under which the tailshaft is examined on a rolling cycle rather than all at once. Collocation: the tailshaft is on continuous survey; the item is credited.
Passed and rerated — the closing status: the shaft is passed within limits, or its survey interval is rerated. Collocation: the shaft is passed within limits; the interval is rerated.

How to drill this cluster

Read the terms in the survey order above — shaft and bearing, weardown, cracks, seals and confirmation — because that is the order a passage presents them and the order that makes each term predict the next. When a reading passage turns on a disputed finding — a shaft condemned though it looked sound, a weardown argued to be within limits — the dispute always lives in one of these four stages. A reader who has the cluster locates the stage instantly and answers from the argument rather than from the individual word. Pair this cluster with the steering gear survey rudder and hydraulic actuator cluster and the broader writing vocabulary precision and collocation discipline guide, and the sterngear vocabulary of a whole passage set becomes a domain you read at speed rather than decode word by word.