We’ve collected the golden rules of bearing fitting that sometimes even the “old pro”-s overlook. The result is premature bearing failure.
1. Choosing the right lubricant – not all grease is good for everything
Many people think that if the cartridge is already full of grease, it will be fine. Then you get a surprise: the grease is too thick, too thin, can’t take the heat or even leaches out. The best part is when they mix two different types of lubricant and start a chemical war inside the bearing.
Always check the machine manufacturer’s recommendation and the type of bearing. If you have high speeds, you need thinner grease, if you have a lot of load, you need heavy duty grease. And don’t mix lithium with calcium, it will turn into lube, not lubrication.
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2. Axis and back tolerances – the hidden culprits
If the shaft is too small, the bearing will rotate loosely on it and micro-motion will start. This stresses the bore or shaft, which can then be re-grooved and repositioned. At the other extreme, it’s so tight that the mechanic almost calls the fire department because the assembly is smoking.
Measure, document, don’t guess. A tenth of a millimetre can make the difference. And if a bearing repeatedly “goes back to the same place”, check to see if the housing or shaft has been damaged in the process. That’s the root of the problem.
3. Education – it’s not embarrassing to learn
Some people think that bearing fitting is the “bottom” of the trade, even though it’s the heartbeat of the machine. One wrong move, and tens of millions of dollars worth of machinery goes down the drain. If you do it smart, you are not just fitting, you are managing machine life.
A quick training, a professional day or a good video is worth more than ten new bearings. Plus, the transfer of experience always comes back – if not at other times, when you have to restart the machine at 2am.
4. Remember the bearing type, not just the part number
This is one of the most important golden rules of bearing fitting! Many people only look at the catalogue code (e.g. 6205-2RS) but don’t pay attention to the internal design, the welds, the material. If, for example, the factory bearing was fitted with C3 internal clearance and you put in a standard fit one, it will be over-tightened. Shorter life, more heat, more annoyance.
5. The logbook is not for show
Write down when, with what, how you fitted the bearing. What grease you used, how long you heated it, what torque you tightened it with. This note may later be the only record of why the machine did or did not hold up. A maintenance history is worth its weight in gold, especially if there is no machine book but there is a fault.
6. Always heat when you need to – but only where and as much as you need to
Anyone who’s worked in a workshop since the 1980’s knows that oil-bath heating and open flame were “high tech” back then. But time has moved on, and we now know that these methods often do more harm than good:
- Oil-bath heating: difficult to control temperatures, can contaminate bearings with lubricant, explosive and polluting.
- Hotplate: heats slowly, often unevenly. One side of the bearing overheats while the other remains cold – leading to internal stresses.
- Open flame (e.g. LPG): inaccurate, unsafe, can lead to overheating and material structural changes. Steel may lose its hardenability.
- Freezing cooling: good in principle, but if there is inadequate protection against condensation, moisture will condense on the cold bearing, accelerating corrosion.
In contrast, induction bearing heaters are accurate, fast, clean and do not expose the bearing to material stresses or contamination. Working with an induction heater is not a gentleman’s job, it’s a professional job that saves bearings. The superheated bearing comes straight from the polished grave into the machine.
We know this is a much debated golden rule of bearing mounting, as old foxes swear by “tried and tested” mounting techniques. However, if there is a safer, faster and more precise method, why not use it?
Simatherm and Simatool bearing fitting tools and instruments are designed to make the life of the maintenance technician easier and to make the tedious tasks clean, precise and quick.
For any questions, feel free to contact us or visit our webshop full of maintenance tools!
Adhering to the golden rules of bearing fitting will determine whether your bearing will make it through the schedule or give out halfway through. Did you know them all?
