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Part ? WTF Series on Ball Bearings

I am not sure what part in the WTF series this was going to be in
but I am providing now as I can only answer so many messages.

So, just to throw this out there since many have inquired.
Determining Max bearing RPM.
You need these calculation's below.
This is for single row deep groove ball bearings.
Speed limit factor = 500,000
Wide, single row bearings have a Width/Section Height ratio of 1.10 - 2.50. Section Height = (O.D. – Bore)/2

Calculate the bearing’s Pitch Diameter (dm) from this formula:

dm = (Bore + OD) ÷ 2 = mm

The limiting speed, Nlim, in RPM is simply calculated:

Nlim = Speed Limit Factor ÷ Dm

Example for a 5x16x5mm:

The bearing’s Pitch Diameter is:

dm = 5mm + 16mm = 21 ÷ 2 = 10.5mm

It's Width to Section Height ratio:

W ÷ SH = 5mm ÷ 16mm - 5mm ÷ 2 = 5.5mm 5mm ÷ 5.5mm = .91

Its limiting speed Nlim:

Speed limit factor is 500,000mm/min ÷ 10.5mm = 47,619 RPM

These factors are based on Oil lubrication, grease is typically 66% of oil limit.

Typically you would not exceed 80% of limit. You would look further into the actual demands on bearing.

A working max RPM for a 5x16x5mm bearing would be 38,095

Running it dry would give you some increase but also generate more heat.
Bearing load can also be a contributing factor.
Seal configuration can effect RPM.
Ball type has some determination BUT Ceramic balls can have a lower RPM the Chrome steel.
Ceramic has less friction but does not always equate to more RPM's
Stainless is also lower RPM.
Play can effect RPM as well as heat.

If you inquire to me for RPM's I will always provide the max working RPM.


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