Chain lubrication: doing it properly
The cheapest reliability upgrade there is, and the one most drives get wrong. Where to put the oil, how much, and which grade.
Lubrication is not maintenance. It is the design.
Every joint in a roller chain is a plain bearing: a pin rotating inside a bush, under load, thousands of times an hour. Run a bearing dry and it destroys itself, and that is precisely what "chain stretch" is. The joints wear, each by a fraction of a millimetre, and the chain grows.
Oil in that joint forms a film that carries the load between pin and bush, cuts the wear rate dramatically, quietens the drive, and carries heat away at speed. No matter how well a transmission is designed, poor lubrication will shorten chain life. It is the cheapest reliability you will ever buy.
Where oiling isn't possible (over food, inside a guard, on a line that can't stop) the answer isn't to run dry. It's to change the chain: see self-lube chain, where the bush is oil-impregnated and lubricates the joint from the inside.
Get these right and most chains outlive their expectations
- Oil the slack side, into the joint. Aim at the gap between the pin link plate and the roller link plate while the chain runs. Oil on the outside of the plates does nothing. It has to reach the pin and bush.
- Use light oil, not grease. Heavy oils and greases can't penetrate the joint clearance. They sit on the surface, collect grit, and make things worse.
- Don't mix oils. Different grades and different makers' oils can react. Pick one and stay with it.
- Enough, and often enough. Under-lubricating is the commonest failure we see. Keep the joints wet and never let them run dry between visits.
Take a section of chain off the drive and look at the pin and bush. Flaking, or a red or dark-brown colour, means poor lubrication. The joint has been running dry and metal is being lost. Clean the chain periodically with a light oil to keep the joints clear.
How to lubricate, and how much
Chain speed decides the method. The faster the chain, the more oil it needs and the less you can rely on doing it by hand.
| Method | How it works | How much |
|---|---|---|
| Type A — manual | Brush or oil can, aimed at the gap between the pin link and roller link on the slack side while running | Top up often enough that the joints never dry, as a rule, roughly every 8 hours of running |
| Type A — drip feed | Drip cup feeding oil into a simple casing | 5–20 drops per minute per strand; the faster the chain, the more drops |
| Type B — oil bath | Chain runs through an oil reservoir in a leak-proof casing | Keep the oil depth (h) at about 6–12 mm. Too much oil overheats and degrades it |
| Type B — slinger disc | A disc on the lower sprocket picks oil from the reservoir and splashes it onto the chain | Disc rim speed above 200 m/min. Oil depth (h) about 12–25 mm. Chain wider than 125 mm needs a disc on both sides |
| Type C — forced (pump) | Oil pump sprays cooled oil continuously inside a leak-proof casing | Number of spray holes = N+1, where N is the number of chain strands |
Manual and drip suit slower drives; oil bath and slinger disc suit medium speeds; forced lubrication is for high-speed, high-load drives. If you are unsure which band your drive falls into, send us the chain size, speed and centre distance and we will advise.
Which grade, by chain size and temperature
Only good-quality oil should be used. Neither heavy oil nor grease is suitable. Viscosity depends on chain size, speed and ambient temperature.
| Chain No. | Types A & B (manual, drip, bath, slinger) | Type C (forced) | ||||||
|---|---|---|---|---|---|---|---|---|
| -10 to 0°C | 0 to 40°C | 40 to 50°C | 50 to 60°C | -10 to 0°C | 0 to 40°C | 40 to 50°C | 50 to 60°C | |
| 50 or less | SAE 10 | SAE 20 | SAE 30 | SAE 40 | SAE 10 | SAE 20 | SAE 30 | SAE 40 |
| 60 – 80 | SAE 20 | SAE 30 | SAE 40 | SAE 50 | SAE 10 | SAE 20 | SAE 30 | SAE 40 |
| 100 | SAE 20 | SAE 30 | SAE 40 | SAE 50 | SAE 20 | SAE 30 | SAE 40 | SAE 50 |
| 120 or more | SAE 30 | SAE 40 | SAE 50 | SAE 50 | SAE 20 | SAE 30 | SAE 40 | SAE 50 |
Chain numbers are ANSI sizes; BS equivalents follow the same bands by pitch (see the cross-reference chart). Outside these temperature ranges (ovens, freezers, chemical environments) talk to us. The answer is usually a different chain specification, not a different oil.
Three environments where oiling fails
- Over food or product. Oil drips. Use self-lube chain with an NSF H1 impregnated bush, or stainless steel with a food-grade regime.
- In dust, grit or bark. Surface oil becomes grinding paste. A dry-film or solid-lubricant treatment, or a sealed specification, will outlast an oiled chain in the same environment.
- Where nobody can reach it. A lubrication schedule that depends on someone remembering will eventually fail. Self-lube chain removes the schedule entirely.
If chains on a drive are wearing out fast, a stronger chain won't help, because the pins and bushes are the same. Lubrication, alignment or contamination is nearly always the real answer. See our fault finder.
Straight answers
Where should I apply chain oil?
Onto the slack side of the chain, aimed into the gap between the pin link plate and the roller link plate, while the chain is running. The oil needs to reach the pin and bush, the bearing surfaces. Oil on the outside of the plates achieves nothing but mess.
How often should I lubricate a roller chain?
Manual lubrication should keep the joints from ever drying, as a rule of thumb, roughly every 8 hours of running. Drip systems should deliver 5 to 20 drops per minute per strand, more at higher speeds. The real test is that the joints are never dry.
Can I use grease on roller chain?
No. Grease and heavy oils cannot penetrate the joint clearance, so they sit on the surface, collect grit and make wear worse. Use a good-quality light oil of the correct viscosity for the chain size and temperature.
How do I know if my chain has been badly lubricated?
Take a section off the drive and inspect the pin and bush. Flaking, or a red or dark-brown discolouration, indicates the joint has been running dry and material is being lost. Once that has happened the chain is on borrowed time.
What oil grade should I use?
It depends on chain size, temperature and lubrication method; see the table above. For most industrial drives at normal temperatures, SAE 20 to SAE 30 covers it. For anything outside the -10 to 60 degrees C range, the answer is usually a different chain, not a different oil.
Not sure what your drive needs?
Send us the chain size, speed and environment, and we will tell you the method, the grade, and whether a self-lube chain would save you the job entirely.