Every bearing has a number stamped on its side. Once you know how to read it, you can tell the type, the size and the sealing at a glance, and you can order a replacement without measuring anything.
The first digit or letters: the type
- 6 deep groove ball bearing (6203, 6309)
- 7 single row angular contact ball bearing (7205)
- 1 self-aligning ball bearing (1205, 1209)
- 2 spherical roller bearing (22205, 22318)
- 29 spherical roller thrust bearing (29412)
- 3 tapered roller bearing (30205, 32210)
- 5 thrust ball bearing (51105, 51109)
- NU, NJ, NUP cylindrical roller bearings (NU205, NU312)
- UC insert bearing for pillow blocks (UC205, UC210)
- HK drawn cup needle roller bearing (HK1512)
- GE spherical plain bearing (GE 60)
The middle digit: how heavy it is
In a ball bearing like 6203, the 2 is the size series. 60 is extra light, 62 is light and 63 is medium. A 6303 has the same bore as a 6203 but is bigger and stronger. Numbers starting 618 or 619 are thin section bearings.
The last two digits: the bore
- 00 = 10 mm
- 01 = 12 mm
- 02 = 15 mm
- 03 = 17 mm
- From 04 upwards, multiply by 5: 04 = 20 mm, 05 = 25 mm, 10 = 50 mm.
So a 6205 has a 25 mm bore and a UC210 has a 50 mm bore.
The letters after the number
- ZZ or 2Z : metal shields on both sides. Good for speed and heat in fairly clean places.
- 2RS or 2RS1 : rubber seals on both sides. Better against dust and water.
- Z or RS (one only): a shield or seal on one side.
- C3 : more internal clearance than normal, used on electric motors and hot-running machines.
- K : tapered bore, for mounting on an adapter sleeve.
- NR : a groove and snap ring on the outer ring.
- M : brass cage. TN : polyamide (fibre) cage.
- B on an angular contact bearing: 40 degree contact angle.
- E : a higher-capacity internal design.
Putting it together
A 6204-2RS C3 is a deep groove ball bearing, light series, 20 mm bore, rubber sealed on both sides, with extra clearance. A 22318 MB is a spherical roller bearing, 90 mm bore, with a brass cage.
When the number is worn off
Measure the bore, outside diameter and width in millimetres and send them to us with a photo. We will identify the bearing and tell you what we have in stock. WhatsApp 0321-2425966.
