Bore Size
Outside Size
Width Size

604 Miniature Ball Bearing 4x12x4 Open MR604

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604 Miniature Ball Bearing

Key Features

604 is an ABEC1 Radial Precision Miniature Ball Bearing manufactured to have both sides open and is pre-lubricated with light oil to allow it to be ready for use upon delivery. Our 600 Series Bearings have a larger OD which can assist in high speed applications as well as facilitate Larger Loads.

Match Numbers / Interchange Numbers

MR604, 604, 7804K102, L-1240, R-1240, DDR1240

Applications / Industries

604 Miniature Ball bearings are used in a range of applications from Robotics to Dental Equipment, Lab Equipment, RC Cars, RC Trucks, RC Helicopters, Electric Motors, High Speed Applications, Automation Control Components, Chemical Lab Equipment, Jewelry and many more

What are Ball Bearings?

A ball bearing is a type of rolling-element bearing that uses roller balls to separate two “races,” or bearing rings. The combination of the roller balls and bearing rings help to reduce surface contact and rotational friction across moving planes to accommodate axial loads.

Ball bearings help to facilitate motion by distributing loads and reducing friction for applications that have a high-speed requirement, ultimately aiding in extending the working life of your equipment.

What are Rolling-Element Bearings?

Rolling-element bearings, commonly called rolling bearings, are bearings that carry a load by utilizing “rolling elements” between two concentric, grooved rings called races. The motion of the bearing races allows for the rolling elements to move with very little resistance and with little slide variance.

Some common types of rolling elements include ball, cylindrical, spherical, barrel, needle, spindle, or tapered.

What is the Difference Between Open, Shielded, and Sealed Rolling Bearings? 

The main difference between open and sealed/ shielded bearings is the application of lubrication. The main difference between sealed and shielded bearings is the presence of a protective enclosure.

  • Sealed and shielded bearings are both lubricated with oil or grease in the bearing factory. However, a rubber sealed bearing protects the bearing by using a seal that contacts the inner and outer race. This provides superior protection at the cost of operating speed and temperature.
  • Open bearings are meant to be lubricated in place, with periodic reapplication of lubrication, based on use.
  • Shielded rolling bearings contain an enclosure that helps to protect the working parts of the bearing from environmental debris that may be introduced and would otherwise reduce the ball bearing speed and lifespan. This metal shield is stamped onto the bearing and only contacts the outer ring, this allows for protection without sacrificing operating speed or temperature.
Online Catalog:
Dimensions & Material
Inner Diameter:
Outer Diameter:
Chrome Steel SAE-52100
Light Oil
ID: 4mm x OD: 12mm x W: 4mm
Product Details
Closure Type:
Grease RPM Limit:
48,000 RPM
Oil RPM Limit :
56,000 RPM
Static Load Rating:
79 lbf
Dynamic Load Rating:
216 lbf
Interchange Numbers:
MR604 , 604 , 7804K102, L-1240, R-1240, DDR1240

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604 ball bearing L1240
604 Miniature Ball Bearing 4x12x4 Open MR604

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