One hand is holding your old broken bearing; the other clutches a new replacement. Over time friction and grease have eroded the part number and you’re looking at something you don’t recognize. You are in a hurry to get back on the water, facing a wall full of numbers that was each stamped by different companies and seem unintelligible.
Time for a bearing crossover chart. It turns the confusing industrial standards into terms you understand.
How to Pick the Right Bearing
Bearings aren’t complicated. Bearings ARE complicated because every manufacturer name them differently. For example, NSK labels bearings with one set of suffixes for shields and seals; SKF does it another way. Timken labels them yet a third way. So a basic open bearing will become shielded or sealed etc., as different manufacturers uses different letters for the same thing. As the chart demonstrates, one company’s double rubber seal may be called something else by another company. And you’re going to guess what they mean without knowing?
Guessing is expensive when it comes to mechanical part. It doesn’t always come down to part numbers. That’s what so many folks miss. I’ve seen people look at two parts from different brands that has the same number and assume they are identical. It won’t because the cage material may be different or the internal clearance may differ between brands even if the part number is identical.
The visual guide breaks out the codes for the suffix, bore, and series code. You have to go beyond the label. Look at the width of the part, the inner diameter, and the outer diameter. Match up the three physical dimensions and you’re good to go. Those three dimensions don’t line up? It is a coincidence that you got the same part number.
Brand selection matter more than most people admit, and it does make a difference. Tighter tolerances and greater precision are found in premium brands such as FAG or SKF. Yes, they’ll cost more but they’ll outlast the cheaper economy brands by far when loaded heavy. Economy brands will save you money initially but may lack the ability to run at speeds or carry heavier load. The chart comparisons indicates some brands are better in terms of precision where others is suited for high-load industrial applications.
It’s up to you to determine the need for your application. Is this for a high-speed spindle? Or something turning slowly on an agricultural piece of equipment? That makes all the difference.
Keep in mind how to install them. You can mess up even the most expensive bearing you purchase by using a hammer. For those unfamiliar with this: always push the appropriate ring when installing bearings. If it’s for a shaft fit then push inward on the inner ring. If it’s for a housing fit then push outward on the outer ring.
If it’s an interference fit, heating the bearing to roughly eighty degrees Celsius will also aid with installation. Don’t use an open flame. That destroys the heat treatment.
And don’t over grease the bearing. Filling it just about halfway (thirty to fifty percent) will be enough. Too much grease increase friction and thus heat which will damage the bearing.
In terms of functionality, shields aren’t equivalent to their suffix counterparts. A shield will provide minimal seal from contaminants and low friction. A seal provides more friction but prevents dirt infiltration. Select the appropriate component for your application. If it’s a dirty work environment, use seals. If you’re in an indoor clean environment, shields may help maintain lower temps and low friction.
You don’t go back to stock because of one part; the whole machine needs to perform as it was originally made. If you put in a mismatched bearing, it will fail too soon. It will also be noisy and vibrate.
Take out the guess work and cross reference the right bearing by checking the numbers and measuring physically for the correct dimension. Now you know the machine will run smooth again. Sounds like a small thing, but it makes a difference.
So take your chart and use it to read the codes, check your metal and put the bearing on the right way. That’s how you get things to keep turning.
