Size a gearbox from the “load”, not from the motor: the reduction ratio is decided by the load speed, and the rated torque by the load torque (including the peaks at start-up and emergency stop) multiplied by a service factor; next, look at whether the ratio of load inertia reflected to the motor side and the backlash can hold the positioning accuracy; then confirm the mounting method and the connections to the motor and the load; then choose lubrication by speed and temperature, and regularly check for oil leaks and temperature rise. This article is about gear reducers installed between a motor and a load, and the selection order common to all types (inline, right-angle, worm and so on); for the details of each type, please inquire. It is divided into 4 stages:
Stage ① | Ratio and torque: load speed, reduction ratio, rated torque and service factor.
Stage ② | Inertia and backlash: inertia reflection, inertia ratio, backlash and positioning.
Stage ③ | Mounting and connection: housing and mounting orientation, connection to the motor, shaft loads.
Stage ④ | Lubrication and life: grease and oil, viscosity and temperature, life and inspection.
For how to measure and order belt drive parts, see “How to Measure a V-Belt? When the Markings Are Worn Off, Follow These Four Steps to Order the Right Part“; this article starts from the point where you have already decided to add a gearbox between the motor and the load. Each stage below covers: how to do it, what public sources say, and what Jiahon can help with; sources, exceptions and this article’s own summaries are in the “Notes” at the end. This is the general case and still depends on the individual case.
Figure 1: The four stages of gearbox selection (schematic, not to scale). ① Ratio and torque — load speed and reduction ratio: calculate the load first, do not look at the motor first; rated torque: including start-up and emergency-stop peaks; service factor: shock, cycling, operating hours. Result of this step: ratio and rated torque settled. ② Inertia and backlash — inertia reflection: divide by the square of the ratio; inertia ratio: motor and load should be close; backlash: maximum or average value. Result: positioning holds. ③ Mounting and connection — housing and orientation: foot, flange, tapped holes; connection to the motor: shaft fully engaged, clamping torque; shaft loads: check radial and axial separately. Result: it connects and can take the loads. ④ Lubrication and life — grease or oil: by pitch line velocity and duty; viscosity and temperature: mineral or synthetic oil; inspection: oil level, leaks, temperature rise. Result: lasts long.
Stage ①: Ratio and torque — calculate the load first, then leave a margin
How to do it:
Decide the specification from the load, not from the motor: matching from the motor may lead you to buy a bigger gearbox than you need; calculating from the load stays closer to the need.
The reduction ratio equals input speed divided by output speed. First write down how fast the load must go and the motor’s rated speed.
Estimate the output torque as input torque times the ratio times the efficiency; a gearbox just trades speed for torque and cannot add power, so compare the product of speed and torque as well (for the formula and a worked example, see the Jiahon product page below). Each additional gear stage usually lowers the output by 1% to 5%.
Look at three kinds of torque: continuous running, the peak at start-up and acceleration, and the maximum at emergency stop. Emergency-stop torque may be much larger than normal deceleration; ask the supplier how many times it can withstand.
Service factor: multiply the required torque by the factor, then choose a gearbox with a large enough rated torque. The factor depends on the shock in the load, whether it runs continuously or cycles and reverses, and how many hours a day it runs.
For continuous running of more than 10 hours a day, or a high ambient temperature, look at thermal capacity separately; with variable frequency drives, thermal capacity drops at low speed.
What public sources say: a 2015 selection article by a power transmission company (vendor-published) says: sizing by the motor may be simpler, but may lead you to buy a bigger gearbox than needed, while sizing by the load stays closer to the application; the service factor is the ratio of the gearbox rating to the application’s requirement; 1.0 means just enough, with no margin; 1.4 is enough for most industrial applications — for example, if the application needs 1,000 inch-pounds (about 113 N·m), choose a gearbox that can take 1,400 inch-pounds (about 158 N·m); high-shock loads increase wear on teeth and bearings and call for a higher factor; uneven loads, even small ones, call for a higher factor than even loads; cycling may call for a higher factor than continuous running, and cycling plus reversing higher still (notes table 1). A 2001 journal article in an industry media outlet (the author works for a gearbox maker) says: makers usually publish the rated torque and acceleration torque, and possibly emergency-stop torque; an emergency stop may decelerate faster than normal, creating a large torque, so ask the supplier how many times it can be applied before teeth break; cyclic applications must compare the peak and rated torque requirements with catalog values; applying the traditional AGMA method to today’s servo applications gives a total safety factor of 3 to 5, making the system bigger, heavier and more expensive than necessary. A selection article by a gearbox maker (maker-published, with product promotion, the page marks a modification on September 1, 2026) says: most driven machines need 150% to 200% of running torque at start-up; each additional gear stage usually lowers output by 1% to 5%; single-stage worm efficiency falls from 90% at 5 to 1 to about 50% at 100 to 1; its service factor table assumes electric motor drive and helical gear reducers, with three columns for less than 3 hours, 3 to 10 hours and more than 10 hours a day — belt conveyors (uniform load) 1.00, 1.25, 1.50, reciprocating pumps 1.50, 1.75, 2.00 — to be checked against the maker’s catalog and gear industry standards; for more than 10 hours a day or an ambient of 100 °F (about 38 °C) or above, compare thermal capacity separately with the continuous load; at low speed on a variable frequency drive, thermal capacity drops because the fans on the motor and gearbox move less air, and how much it drops should be confirmed with the supplier (notes table 1).
What Jiahon Can Help With:
Inline gearbox: the product page says it is a reducer with the input shaft and output shaft arranged coaxially. Its specification table lists the “usual specification ranges” for this kind of reducer, not the specifications of a single model: single-stage ratios 3:1 to 10:1, two-stage 9:1 to 100:1; output torque 5 to 500 N·m; input speed 500 to 6,000 rpm; transmission efficiency varies with type — planetary single-stage 95% to 97%, two-stage 90% to 94%, parallel shaft 92% to 95%, harmonic 70% to 90%. The product page also says the stock item on this page is one model (not listed here), and other types and ratios can be quoted; the type, ratio, rated torque and efficiency of this stock model itself are not stated on the product page; please inquire.
The worked example on the same page (the source of the “output torque” point above): motor 3,000 rpm, 1 N·m; the target output is 100 rpm, 50 N·m. The output at 30:1, calculated at an efficiency of 0.95, is just 28.5 N·m, which is not enough; comparing power, the load needs about 524 W, while this motor has just about 314 W. The product page’s conclusion is to keep the ratio at 30:1 and change the motor to one with a rated torque of about 1.75 N·m and power of about 550 W or more.
AC servo motor: the product page lists rated speed 3,000 rpm, rated torque 4.77 N·m, peak torque 14.3 N·m (written as 3 times rated); it can be used to check the gearbox input; for which gearbox to pair it with, please inquire.
Stepper motor: the product page explains that stepper motor torque drops markedly at high speed, and its specification table gives a maximum holding torque of 1.5 N·m. So for the input torque to the gearbox, look at the torque at the actual speed; please inquire.
Stage ②: Inertia and backlash — for accurate positioning, look at both together
How to do it:
Inertia reflection: the load inertia reflected through the gearbox to the motor side is divided by the square of the reduction ratio.
Inertia ratio: the ratio of the reflected load inertia to the motor’s own inertia. The motor and load inertias should be close; the upper limit sources often mention is 10 to 1: beyond it, the servo system may have difficulty controlling acceleration and deceleration; for fine-tuned control, below 10 to 1 is preferable.
To lower the inertia ratio, choose a gearbox with a higher ratio, but it is limited by the rated input speed. A single-stage inline planetary reducer tops out at about 10 to 1; higher ratios need another stage, which adds cost.
Backlash: the clearance left between teeth for thermal expansion and manufacturing error, which affects the accuracy of the stopping position. Precision positioning needs a low-backlash gearbox and dual-loop feedback.
Ask clearly about backlash: whether the value given is a maximum or an average; makers may apply a small load first so the tooth faces are in full contact before measuring, so ask what percentage of rated or acceleration torque that load is.
If backlash is too large, impact forces are high during cyclic motion, and teeth may fail early.
Figure 2: Load inertia reflected to the motor side (schematic, not to scale). Load (large inertia) — gearbox (reduction ratio) — motor (its own inertia). Load inertia seen at the motor side = load inertia ÷ square of the reduction ratio. Inertia ratio = reflected load inertia ÷ the motor’s own inertia.
What public sources say: the 2001 journal article mentioned above says: a gearbox reduces the inertia ratio by the square of the reduction ratio — for example, load 100, ratio 5 to 1, motor 1 gives an inertia ratio of 4 to 1; for good system response, motor and load inertias should be close, and with an inertia ratio above 10 to 1, the servo system may have difficulty controlling acceleration and deceleration of the load; to reduce inertia substantially, choose a higher ratio, but the rated input speed limits the usable ratio; the upper limit of a single-stage inline planetary ratio is 10 to 1, and higher ratios need an additional stage, adding cost; right-angle types are more expensive because they are harder to assemble; backlash is the clearance between teeth left to compensate for thermal expansion and manufacturing error, and you should confirm whether the maker gives a maximum or an average value, and how large a load is used for measurement; backlash affects the accuracy of the stopping position, and such applications use dual-loop feedback and low-backlash gearboxes; excessive backlash causes high impact forces on the tooth faces in cyclic motion, leading to early tooth failure; the article does not give a numerical upper limit for backlash (notes table 2). The 2015 power transmission company article says: for fine-tuned control, an inertia mismatch of less than 10 to 1 is preferable, and control engineers may require less. A 2002 journal article (no author named) says: planetary reducers for servos are made to tight tolerances with low backlash, and high torsional stiffness keeps lost motion to a minimum; even as motor torque density keeps rising, servo gearheads are usually still needed to match inertia, increase motor torque and lower motor speed; the article does not give figures for backlash or stiffness.
What Jiahon Can Help With:
Inline gearbox: the specification table lists usual backlash ranges: standard grade under 30 arcmin, precision grade under 5 arcmin, ultra-precision under 1 arcmin (harmonic). The measurement method (maximum or average, with how large a load), the backlash of this stock model, the torsional stiffness and the gearbox’s own inertia are not stated on the product page; please inquire.
Stepper motor: the specification table lists rotor inertia 175×10⁻⁷ kg·m². The table does not say whether this figure includes the reduction part; please inquire.
Servo drive, another servo drive page: neither page states the allowable inertia ratio range; please inquire. Both pages say they should be paired with motors of the same series (one says the whole series must be paired, the other recommends pairing to secure encoder communication); the AC servo motor page in Stage ① says it pairs with drives of its own series. So for how to pair motors and drives, please inquire. Auto-tuning: one page says three models have it built in; the other page does not say.
Optical encoder: this page is about an optical linear encoder readhead (used with an optical scale, for position feedback on a linear axis): resolution range 5 µm to 50 nm, maximum speed 10 m/s. There is no rotary encoder on this page; whether load-side feedback can be done this way, please inquire.
Stage ③: Mounting and connection — it has to connect and take the loads
How to do it:
Housing and mounting: see whether it is foot-mounted, output-flange or tapped-hole mounting, and which one can mount directly on the existing frame; with tapped holes, you may not need a special bracket.
Mounting orientation: horizontal, vertical shaft down, vertical shaft up — the positions of the fill, breather and drain holes are designed for an orientation; for non-standard orientations, makers often have to move the breather, change the oil quantity or add oil passages.
Connection to the motor: the motor shaft must be long enough to fully engage with the coupling, or the input side will slip. Planetary servo gearheads are often connected directly to the servo motor with a zero-backlash clamp; follow the maker’s mounting procedure and recommended clamping torque, because slipping damages the shaft and gears.
Coupling shaft misalignment should be small: for general use at about 1,800 rpm, the target is 0.002 to 0.005 inch (about 0.05 to 0.13 mm), and tighter at higher speeds.
Shaft loads: sprockets, pulleys or pinions on the output shaft mostly create higher radial forces; helical gears also create axial forces. Check the radial and axial limits separately, and check again when both act at the same time. Shaft loads beyond the rating will damage the gearbox.
What public sources say: the 2015 power transmission company article says: the housing may be foot-mounted, output-flange, or have tapped holes on one or more faces, and choosing the right one can avoid a special frame or bracket — for example, no need for an L-shaped bracket around the output shaft; the motor shaft must fit into the gearbox, and the shaft must be long enough to fully engage the coupling; without full engagement, the input side may slip; output-side mechanisms such as sprockets, pulleys or pinions mostly create high radial loads, and helical gears may also create axial loads; the overhung load rating is the force the output shaft can take, and if the application’s load exceeds the rating, the gearbox will be damaged (notes table 3). The 2002 journal article says: planetary servo gearheads are usually connected directly to the servo motor with a zero-backlash clamp; follow the maker’s mounting procedure and recommended clamping torque carefully, because slipping damages the shaft and gears. The gearbox maker’s article mentioned above says: overhung load factors are 1.0 for sprockets, 1.25 for spur or helical gears, 1.5 for V-belts and 2.5 for flat belts; most catalogs list radial and axial limits separately, both must be checked, and checked again when both act together; mounting orientations are given by IEC 60034-7 codes, for example B3 is foot-mounted horizontal shaft, B5 flange horizontal shaft, V5 vertical shaft down and V6 vertical shaft up; a gearbox built for B3 has its fill, breather and drain holes in the B3 positions, and flipped to V5 or B8 the holes end up in the wrong places, so makers often have to move the breather, change the oil quantity or add oil passages; for coupling shaft misalignment, the target for general applications at about 1,800 rpm is 0.002 to 0.005 inch, and tighter at higher speeds (notes table 3).
What Jiahon Can Help With:
Inline gearbox: the specification table says motor-side flanges come in IEC, NEMA and custom. The housing form, usable mounting orientations, input connection to the motor and overhung load rating of this stock model are not stated on the product page; please inquire.
AC servo motor: the product page lists flange size 100 mm, shaft diameter 19 mm (with keyway and tapped hole); there is also a shaft-end version with an oil seal, which the product page says is used for vertical mounting or dusty environments.
Stepper motor: the product page lists frame size 56.4 mm (written as NEMA 23 equivalent size), with lead wire connection.
Stage ④: Lubrication and life — to last long, watch the oil and the temperature rise
How to do it:
Grease or oil: grease for low speed and intermittent duty; oil bath splash for higher speeds; forced circulation for higher speeds still. The ranges listed in the sources overlap, and the actual boundaries follow the maker’s data.
Advantages of grease: synthetic grease stays distributed, needs no regreasing, and allows mounting in any orientation.
Viscosity and temperature: under heavy load, higher viscosity protects better; at high speed, higher viscosity adds drag. Mineral and synthetic oils each have a usable temperature range; where temperatures stay very high for long or the environment is very cold, consider synthetic oil.
Do not mix: mixing greases with different thickeners may make them liquefy or harden. To switch to a new lubricant, try it on one component first and watch temperature, vibration and leaks.
Quantity: too much and too little both cause problems.
Life: look at the rated bearing life (often given as L10 hours). Ask the supplier under what conditions the rated life was calculated (this sentence is this article’s own summary).
Oil changes and inspection: track the oil change interval with oil analysis rather than relying on fixed times; common causes of high temperature are wrong viscosity, too little oil or insufficient cooling, and the first item on the troubleshooting list is checking the oil level; also check leaks and temperature rise regularly.
Figure 3: Lubrication method and speed (schematic, not to scale; the pitch line velocity ranges of the three methods in the source overlap — figures in notes table 4). From low-speed intermittent duty to high speed: grease — synthetic grease stays distributed, no regreasing, any mounting orientation; oil bath splash — the gears throw up the oil, a common method, watch the oil level; forced circulation — oil fed by a pump, for higher speeds.
What public sources say: the 2002 journal article mentioned above says: the bearing life of a standard gearbox is 5,000 hours (L10), and some planetary servo gearheads offer 20,000 hours; synthetic grease stays distributed and needs no regreasing; using grease also allows the gearbox to be mounted in any orientation. The gearbox maker’s lubrication article mentioned above (maker-published, with product promotion, the page marks a modification on September 1, 2026) says: grease works well at pitch line velocities below 6 meters per second and intermittent duty, the fill is often 30% to 50% of the cavity, and the regreasing interval 500 to 5,000 hours; oil bath splash is the common method in industrial gearboxes, at 4 to 15 meters per second; high-speed gearboxes above 12 meters per second need forced circulation (these three ranges overlap, and the article does not explain how to choose between them); under heavy load, high viscosity protects better, but drag increases at high speed, and the article lists a viscosity grade comparison from VG 32 to 46 for high speed and light load to VG 220 to 320 for heavy load; mineral oil can be used from −10 to 90 °C, and synthetic oil from −46 to 125 °C; where temperatures stay above 90 °C or the environment is below −20 °C and similar, consider synthetic oil; oil change intervals should follow the trend from oil analysis, not fixed times; gearbox overheating points to the wrong viscosity, too little oil or insufficient cooling, and the first item on the checklist is checking the oil level (notes table 4). A 2013 lubrication article on an automation association website (the author is marked as a contributing editor) says: mixing greases with different thickeners may make them liquefy and accelerate wear, or solidify and possibly burn out a component — polyurea and lithium greases cannot be mixed; to switch to a new lubricant, try it on one component first and watch temperature, vibration and leaks in the first period; too much grease causes problems, and too little leaves some surfaces unprotected; bearings in high-speed applications may be filled to just 20% of the open volume (notes table 4).
What Jiahon Can Help With:
- Inline gearbox: the specification table lists operating temperature −10 to 90 °C (standard); lubrication: small sizes are sealed for life, and medium and large sizes are the type that needs oil maintenance, with ISO VG 220 to 320 gear oil. The product page also says: small planetary and harmonic types are mostly sealed for life, and the whole unit is replaced on failure; medium and large parallel shaft and worm types have the oil changed every 2,000 to 5,000 hours (the page marks this as a general rule of thumb, with the maker’s specification taking precedence); stop and inspect if any of these appear: housing above 85 °C, abnormal running noise, oil turning black or foaming, or oil leaking at the shaft end. Which lubrication this stock model uses, and its rated life, are not stated on the product page; please inquire.
When you need to match a type, please prepare six items first: the load speed and torque (including start-up and emergency-stop peaks); the load inertia; the positioning accuracy required; the mounting orientation and what is connected to the shaft end; the operating hours per day; and the ambient temperature. You are welcome to contact Jiahon.
Further reading
To go through the related process steps together, you can read these next:
- “How to Measure a V-Belt? When the Markings Are Worn Off, Follow These Four Steps to Order the Right Part“: how to measure the size and order the right part once the markings on the belt are worn off
Further reading: “Servo Motor vs Gearbox“, “VFD vs Gearbox“
Conveying and lifting: loaders/unloaders, rails and peripheral equipment
Where an SMT line needs something “slow but strong”, a motor plus gearbox is commonly used: magazine lifting in loaders/unloaders, rail width adjustment, conveyor drives, and the mesh belts of peripheral equipment such as washers and ovens. When choosing a gearbox, the SMT floor has two more things to think about:
Whether it stops accurately. Magazine lifting and rail width adjustment both have to stop at fixed positions; with too much backlash, the stopping position drifts, and boards cannot enter the rail or jam at the magazine mouth (for backlash, see Stage ② of this article).
Long periods of continuous running at low speed. Conveyors and mesh belts often run continuously at low speed all day, so lubrication and temperature rise should be checked regularly per the maker’s recommendations (see Stage ④); the belt speed of peripheral equipment is itself a process parameter — for example, an inline washer catalog in our engineering data lists an adjustable belt speed range — and the drive system has to run stably across the whole range.
For equipment maintenance, first list each machine’s gearbox model, ratio and lubrication interval in the spare parts list.
Notes: sources and exceptions
The following is for readers who need to check; skipping it does not affect the approach above. Where your machine specifications, the gearbox’s written specifications or safety standards differ from this article, follow them.
Where each stage comes from
| Source | Which stages and content | Source |
|---|---|---|
| Source 1 | Stages ① to ③: sizing by load, service factor and load types, inertia ratio for fine-tuned control, housing, motor shaft engagement, shaft loads | A selection article by a power transmission company (March 25, 2015; vendor-published, reprinted on an automation association website) |
| Source 2 | Stages ① to ②: three kinds of torque, emergency stop, traditional method, inertia reflection, reduction ratio, backlash and positioning | A journal article in an industry media outlet (July 12, 2001; the author works for a gearbox maker; older) |
| Source 3 | Stages ①, ③: start-up torque, efficiency, service factor table, thermal capacity, overhung load factors, mounting orientation, shaft misalignment | A selection article by a gearbox maker (the page marks a modification on September 1, 2026; maker-published, with product promotion) |
| Source 4 | Stages ② to ④: backlash and stiffness of planetary reducers, zero-backlash clamps, synthetic grease, bearing life | A journal article in an industry media outlet (March 1, 2002; no author named; older) |
| Source 5 | Stage ④: mixing greases, changing lubricants, quantity | A lubrication article on an automation association website (November 13, 2013; the author is marked as a contributing editor) |
| Source 6 | Stage ④: ranges for grease and oil, fill and regreasing, temperature, viscosity, oil changes, overheating | A lubrication article by the same maker (the page marks a modification on September 1, 2026; maker-published, with product promotion) |
| Jiahon data | “What Jiahon Can Help With”, and the formula and worked example in Stage ① | Jiahon product pages |
Table 1 | Ratio, torque and service factor
| Item | Content | Source |
|---|---|---|
| Basis of sizing | Sizing by load stays closer to the application than sizing by motor; sizing by motor may lead to buying a bigger gearbox than needed | Source 1 |
| Service factor | Ratio of the gearbox rating to the application’s requirement; 1.0 just enough, no margin; 1.4 enough for most industrial applications; example: needing 1,000 inch-pounds, choose one that can take 1,400 inch-pounds | Sources 1, 3 |
| Load types | Shock increases tooth and bearing wear, so raise the factor; uneven loads, even small ones, take a higher factor than even loads; cycling may be higher than continuous; cycling plus reversing higher still | Source 1 |
| Start-up and efficiency | Start-up needs 150% to 200% of running torque; each additional stage usually lowers output by 1% to 5%; single-stage worm falls from 90% at 5 to 1 to about 50% at 100 to 1 | Source 3 |
| Factor examples | Electric motor drive, helical reducers, less than 3 hours, 3 to 10 hours, more than 10 hours a day: belt conveyor (uniform load) 1.00, 1.25, 1.50; reciprocating pump 1.50, 1.75, 2.00; check against the maker’s catalog and gear industry standards | Source 3 |
| Thermal capacity | More than 10 hours a day or an ambient of 100 °F (about 38 °C) or above: compare separately with the continuous load; drops at low speed on a variable frequency drive (less fan air), confirm with the supplier how much | Source 3 |
| Three kinds of torque | Makers usually publish rated torque and acceleration torque, possibly emergency-stop torque; an emergency stop may create a large torque, ask how many times before teeth break; cyclic applications compare peak and rated torque with catalog values | Source 2 |
| Traditional method | The AGMA method applied to today’s servo applications gives a total safety factor of 3 to 5, making the system bigger, heavier and more expensive | Source 2 |
Table 2 | Inertia and backlash
| Item | Content | Source |
|---|---|---|
| Inertia reflection | The inertia ratio becomes one over the square of the reduction ratio; example: load 100, 5 to 1, motor 1 gives 4 to 1 | Source 2 |
| Inertia ratio | Motor and load inertia should be close; above 10 to 1 acceleration and deceleration may be hard to control. Another source says below 10 to 1 is preferable for fine-tuned control, and less may be required | Sources 1, 2 |
| Reduction ratio | To lower inertia choose a higher ratio, limited by the rated input speed; single-stage inline planetary tops out at 10 to 1, higher needs another stage and adds cost; right-angle types are harder to assemble and more expensive | Source 2 |
| Backlash | Left for thermal expansion and manufacturing error; ask whether maximum or average; makers may apply a small load before measuring, ask what percentage of rated or acceleration torque it is; affects the accuracy of the stopping position; no numerical upper limit given | Source 2 |
| Positioning and failure | Such applications use dual-loop feedback and low-backlash gearboxes; excessive backlash means high impact forces in cyclic motion and early tooth failure | Source 2 |
| Planetary reducers | Tight tolerances, low backlash; high torsional stiffness keeps lost motion minimal; servo gearheads are still often needed to match inertia, add torque and lower speed; no figures | Source 4 |
Table 3 | Mounting and connection
| Item | Content | Source |
|---|---|---|
| Housing | Foot, output flange, tapped holes on one or more faces; choosing correctly can avoid a special frame or bracket | Source 1 |
| Motor connection | Motor shaft long enough to fully engage the coupling, otherwise the input slips; planetary servo gearheads often connect directly to the servo motor with a zero-backlash clamp; follow the maker’s procedure and clamping torque, slipping damages shaft and gears | Sources 1, 4 |
| Shaft loads | Sprockets, pulleys and pinions mostly create high radial loads; helical gears may create axial loads; beyond the rating, the gearbox is damaged | Source 1 |
| Overhung load factors | Sprocket 1.0, spur or helical gear 1.25, V-belt 1.5, flat belt 2.5; radial and axial limits listed separately, check both; check again when acting together | Source 3 |
| Mounting orientation | IEC 60034-7 codes: B3 foot-mounted horizontal shaft, B5 flange horizontal shaft, B6 and B7 wall-mounted, B8 ceiling-mounted, V5 vertical shaft down, V6 vertical shaft up; hole positions designed by code; non-standard orientations may need the breather moved, the oil quantity changed or oil passages added | Source 3 |
| Shaft misalignment | General use at about 1,800 rpm: target at the coupling 0.002 to 0.005 inch; tighter at higher speeds | Source 3 |
Table 4 | Lubrication and life
| Item | Content | Source |
|---|---|---|
| Life | Standard gearbox bearing life 5,000 hours (L10); some planetary servo gearheads 20,000 hours | Source 4 |
| Synthetic grease | Stays distributed, no regreasing; also allows mounting in any orientation | Source 4 |
| Ranges for grease and oil | Grease: works well below 6 meters per second pitch line velocity and intermittent duty; oil bath splash: 4 to 15 meters per second; forced circulation: above 12 meters per second (the ranges overlap; the article does not explain how to choose) | Source 6 |
| Fill and regreasing | Grease fill often 30% to 50% of the cavity; regreasing interval 500 to 5,000 hours | Source 6 |
| Temperature | Mineral oil −10 to 90 °C; synthetic oil −46 to 125 °C; where it stays above 90 °C or the environment is below −20 °C and similar, synthetic oil is suggested | Source 6 |
| Viscosity | Under heavy load, high viscosity protects better; at high speed, drag increases; high speed light load VG 32 to 46, general industrial VG 68 to 150, heavy load VG 220 to 320, extreme or shock loads VG 460 and above | Source 6 |
| Oil changes and overheating | Use oil analysis trends instead of fixed times, starting from the maker’s recommendation and adjusting; overheating points to wrong viscosity, too little oil, insufficient cooling; the first item on the checklist is checking the oil level | Source 6 |
| Mixing and changing | Mixing different thickeners may liquefy (accelerating wear) or solidify (possibly burning out components); polyurea and lithium cannot be mixed; when switching to a new lubricant, try it on one component first and watch temperature, vibration and leaks | Source 5 |
| Quantity | Too much causes problems, too little leaves some surfaces unprotected; bearings in high-speed applications may be filled to just 20% of the open volume | Source 5 |
Standards referenced
For the standards cited in this article, please follow the current revision from each publishing body.
AGMA 6010 (the number is mentioned in source 3; this article did not read the full text)
Publisher: AGMA (American Gear Manufacturers Association)IEC 60034-7 mounting arrangement codes (source 3 lists the codes; this article did not read the full standard)
Publisher: IEC (International Electrotechnical Commission)
This is the general case and still depends on the individual case.
Exceptions and limits
What was seen and what was not: this article looked at 1 selection article by a power transmission company (2015), 2 journal articles in an industry media outlet (2001, 2002), 1 selection article and 1 lubrication article by the same gearbox maker (pages marked as modified on September 1, 2026), and 1 lubrication article on an automation association website (2013). The full texts of AGMA 6010 and IEC 60034-7 were not read, nor the specification sheet of the stock model of Jiahon’s inline gearbox.
Sources with a position: source 1 is vendor-published; sources 3 and 6 are maker-published with product promotion; the author of source 2 works for a gearbox maker. This article takes just general statements and the figures they themselves wrote.
The figures are examples: service factors, efficiency, the 10 to 1 inertia ratio, grease fill, regreasing intervals, temperature ranges, viscosity grades, overhung load factors and shaft misalignment are all examples or rules of thumb from the sources, not selection thresholds; they differ between makers and types. Sources 2 and 4 are articles from 2001 and 2002 and serve just as explanations of principle.
Conversions: the conversions of inch-pounds, inches and Fahrenheit were done by this article (1 inch-pound is about 0.113 N·m, 1 inch is about 25.4 mm, 100 °F is about 38 °C), rounded to whole numbers or two significant figures; the sources use imperial units.
This article’s own summary: in Stage ④, “ask the supplier under what conditions the rated life was calculated” is this article’s suggested practice, not directly written in the sources; in Figure 3, “from low to high speed: grease, oil bath splash, forced circulation” is a schematic drawn from the three speed ranges of source 6, without specific figures and without drawing the overlap; the output torque formula and worked example in Stage ① come from Jiahon’s own product page explanation, not from an outside source. The other sentences can be matched to statements in the sources.
Names of standards: AGMA 6010 and IEC 60034-7 are numbers mentioned in source 3; this article just writes the numbers without having read the full texts; the meanings of codes such as B3 and V5 follow source 3’s explanation.
Scope: this article discusses just the selection order common to gear reducers installed between a motor and a load; it does not discuss the details and selection of each type (planetary, harmonic, worm, right-angle and so on), nor prices and lead times.
Equipment and products: the figures and statements in “What Jiahon Can Help With” were read from the text of the product pages on October 13, 2026; the product images were not looked at and no specification sheets were read, so they were not verified by this article; the specification is as on the product page, and for what the product page does not state, please inquire. The model numbers, series codes and brands on the product pages are not written here; the product pages’ “also see”, “application scenes” and marketing explanations are the pages’ own and were not quoted. The specification table on the inline gearbox page says itself that it gives the “usual specification ranges” for this kind of reducer, and the stock item is the one model stated on the page; this is the one gearbox product page on the site. The short description field of the stepper motor page contains words such as “geared stepper motor”, “planetary gearbox” and “ratio 1 to 36”, but the specification table in the body does not explain the reduction part; this article follows the table in the body. The optical encoder page is a linear readhead, not a rotary type.
This article is a summary for the general case, not a restatement of standard clauses, and not an endorsement of any maker, equipment supplier or service provider, nor an assurance for your equipment and process. Please take your machine specifications, the gearbox’s written specifications and safety standards, and your own validation as the reference; this is the general case and still depends on the individual case.