Bevel Gearbox Guide: Choosing a T Series Right-Angle Gearbox
When to use a spiral bevel gearbox instead of a right-angle reducer, how the ten T series sizes compare, and how to read the shaft arrangement, ratio and mounting position into one model code.
A bevel gearbox is not a gear reducer with a corner in it. It is a different machine with a different job: taking one rotation and sending it off at 90 degrees, often at the same speed it came in, and often to more than one output shaft. Yanfeng Group Co., Ltd. builds the T series spiral bevel gearbox in Pingyang, Wenzhou — ten sizes, T2 to T25, with standard ratios from 1:1 to 5:1 — and the most common sizing mistake we see is a buyer ordering a right-angle reducer when what the machine actually needs is a right-angle box. This guide sets out the difference, then runs the selection in the order our catalogue does. Every figure below comes from the T series page and the T series catalogue PDF.
Key definitions
- Spiral bevel gearbox (steering box): a pair of spiral bevel gears — pinion and crown wheel — in a square housing, turning the drive through 90 degrees. It transmits power; reducing speed is optional.
- Ratio: the speed change between the two shafts. On the T series this is 1:1 to 5:1, so 1:1 — direction changed, speed unchanged — is a legitimate and common choice.
- Shaft arrangement: how many shafts the box has and which faces they come out of. The T series covers two-, three- and four-shaft layouts.
- Mounting position: the orientation the box is bolted down in, B3, B6, B7, B8, V5 or V6, which fixes where the shafts point.
- Rated output torque (MN2): the torque a size is rated for continuously at a given input speed and ratio — the figure in the selection table, not a peak.
- Service factor: the multiplier applied to the required torque for load type and daily running hours before a size is chosen.
- Line shaft: the common shaft that carries one drive to several boxes, typical in lifting and conveying systems.
T, K or S: which right-angle unit you actually need
All three of these turn the drive through 90 degrees, and they are not interchangeable.
| T series spiral bevel gearbox | K series helical-bevel reducer | S series helical-worm reducer | |
|---|---|---|---|
| What it is for | changing direction, splitting a drive | reducing speed at a right angle | reducing speed at a high ratio in a small box |
| Ratio range | 1:1 to 5:1 | approx. 5.36 to 197 | approx. 6.8 to 290 |
| Sizes | T2–T25 (10) | K37–K187 (12) | S37–S97 (7) |
| Motor | none; driven from a shaft | bare unit or geared motor, 0.18–200 kW | bare unit or geared motor, 0.12–22 kW |
| Output torque | approx. 11.6–3,499 N·m rated | 156–49,400 N·m | 93–3,990 N·m |
| Rotation | forward and reverse | one load direction; state it when ordering | forward and reverse |
| Can increase speed | yes, by driving the other shaft | no | no |
| Multiple output shafts | yes, 2, 3 or 4 shafts | no | no |
The practical test is one question: do you need the speed changed? If yes, and by a factor of six or more, you want the K or S series and should start from our gear reducer selection guide. If you need the drive to arrive somewhere else — at a right angle, or at three places at once, at or near the speed it left the motor — the T series is the right machine and a reducer is the wrong one.
The ten sizes
| Size | Weight (excluding shafts and accessories) |
|---|---|
| T2 | 2 kg |
| T4 | 10 kg |
| T6 | 21 kg |
| T7 | 32 kg |
| T8 | 49 kg |
| T10 | 78 kg |
| T12 | 124 kg |
| T16 | 188 kg |
| T20 | 297 kg |
| T25 | 488 kg |
Weight is the quickest proxy for capacity across the range, and the spread is wide: the largest box is roughly 240 times the mass of the smallest. The torque figures that matter are read from the catalogue tables, which are indexed by input speed from 10 to 1450 r/min:
- At 1:1 and 1450 r/min, rated output torque MN2 runs from about 11.6 N·m on the T2 to about 2,274 N·m on the T20; the T25 is rated at about 3,499 N·m at 870 r/min.
- Rated torque rises as input speed falls. At the bottom of the speed range the T25 reaches about 5,713 N·m at 1:1 and 10 r/min.
That second point is the one to plan around. A box selected on its 1450 r/min rating is being judged at its weakest; if your line shaft turns slowly, the same size carries considerably more.
Choosing a T series gearbox in six steps
- Fix the torque at the box, not at the motor. Work out the torque the box actually passes. Where boxes are chained, do this for each one separately — see the section below.
- Apply the service factor. The catalogue gives a factor from 1.00 to 2.00 by load type — uniform load, moderate shock, heavy shock — and daily running hours, banded as up to 2 hours, 2 to 10 hours and 10 to 24 hours. Where starts and stops exceed ten per hour, the higher bracketed values apply. Multiply the required torque by this factor before looking at a size.
- Choose the ratio, and do not assume it has to reduce. Standard ratios are 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 4:1 and 5:1. If the drive speed is already right, 1:1 is the correct answer and keeps the box small.
- Decide which shaft you drive. On any ratio other than 1:1, driving the horizontal shaft gives speed reduction and driving the vertical shaft gives a speed increase. State this with the order: once the mounting position and dimensions are settled, the positions of the two shafts cannot be changed afterwards.
- Pick the shaft arrangement. Two-shaft layouts (I-LR, I-L, I-R, I-U, I-D, I-UD, U-LR, D-LR, and the matching -O reversed-rotation variants) cover a simple corner. Three- and four-shaft layouts (I-I-LR, I-I-UD, U-D-LR and their variants) let one box feed two or three directions, which is usually cheaper and tidier than two boxes and a coupling.
- Pick the mounting position. B3, B6, B7, B8, V5 and V6 are available. This is set by the machine frame, and it interacts with step 4, so settle both together.
The result is a single model designation in the form YF T 12 2:1 D-LR B3 — series, size, ratio, shaft arrangement, mounting position. A supplier who cannot return that string, with a rated torque against it, has not done the selection.
Chaining boxes on one line shaft
Multi-box systems are the normal case, not the exception — a lifting platform driven by several screw jacks, or a conveyor line with drives at intervals. One rule governs them: the box nearest the motor carries the sum of the torque passing to every box downstream of it. Size it for the whole system, not for the single machine standing beside it. The boxes further down the chain are each sized for their own share, which is why a line often mixes two or three frame sizes rather than repeating one.
This is the same rule set out in our screw jack selection guide, where T series boxes distribute one drive across up to eight SWL screw jacks and a separate linkage factor derates each jack. If you are specifying a jack system, size the jacks first and the bevel boxes second: the jack count sets the torque the first box has to carry.
Construction, and what to ask us for
The housing is a square casting with a removable end cover on each face, which is what makes the three- and four-shaft arrangements possible from one basic body. Inside, the spiral bevel pinion and crown wheel run on rolling bearings with lip oil seals, bearing housings, shim rings, flat keys and a breather plug — about 40 parts in the exploded view. The gears are premium alloy steel, precision ground for meshing accuracy; the bearings are high-grade ball bearings; the finish is the three-layer high-density polymer paint used across our range, which seals out dust and tolerates high temperature. The catalogue describes the result as a box that transmits large forces, runs in both directions, and does so with low vibration and low noise.
One note on the catalogue itself: the rated input power row (PN1) is partly obscured in the printed copy, so do not size a drive from it. Ask us for the input power figure for the size and ratio you are considering and we will confirm it against the master tables.
Our recommendation
Decide the machine class before the size. If the drive has to change direction and the speed is already correct, specify a T series box at 1:1 and stop; fitting a reducer there adds ratio you then have to undo elsewhere. If the speed has to come down by a factor of six or more, the K or S series is the right unit, and if both have to happen in one line, a reducer feeding one or more T boxes is usually cheaper than several motorised right-angle units. For the factory, machining and certification checks behind all nine of our reducer series, see the supplier verification guide; the gear grinding and inspection equipment is listed on our production capacity page.
Send the torque at each box, the input speed, the required ratio, the number of boxes in the line, the load type and the daily running hours through the enquiry form. Our Reducer Sales department and engineers return a size, a shaft arrangement, a complete model designation and a dimension drawing. The full range is listed under gear reducers; office hours are Monday to Saturday 08:00–17:30 and Sunday 09:00–17:30, China Standard Time (UTC+8).
Frequently asked questions
- What is the difference between a bevel gearbox and a bevel gear reducer?
- A bevel gearbox such as the T series turns the drive through 90 degrees with a pair of spiral bevel gears, at ratios from 1:1 to 5:1, and has no motor of its own. A bevel gear reducer such as the K series is a motorised unit whose job is to reduce speed, with ratios from about 5.36 to 197. If you need direction changed and speed left alone, you need the gearbox, not the reducer.
- Can a T series bevel gearbox increase speed instead of reducing it?
- Yes. The same box works either way on any ratio other than 1:1, and which shaft you drive decides it: driving the horizontal shaft reduces speed, driving the vertical shaft increases it. Say which at the order stage, because once the mounting position and dimensions are fixed the two shaft positions cannot be swapped.
- What sizes does the T series come in?
- Ten frame sizes, T2 to T25, weighing from 2 kg on the T2 to 488 kg on the T25. Rated output torque at 1:1 and 1450 r/min runs from about 11.6 N·m on the T2 to about 2,274 N·m on the T20, with the T25 rated at about 3,499 N·m at 870 r/min.
- How many bevel gearboxes can be chained on one line shaft?
- There is no fixed limit, but there is a sizing rule: the box nearest the motor carries the sum of the torque passing to every box downstream of it, so it is sized for the whole system rather than for the machine it sits next to. Check each box in the chain against its own share, then check the first one against the total.
- Can a T series gearbox run in both directions?
- Yes. The spiral bevel pair is suitable for forward and reverse rotation, which is one of the differences from the K series helical-bevel reducer — that unit bears load in one direction only, so its rotation direction has to be stated when ordering.