Common types of bearings used in machine tool spindles include:

1. Deep groove ball bearings: This type of bearing is mainly used to bear radial loads. Since their clearance is adjusted before leaving the factory and the clearance is not adjustable, they are often used in places where precision is not required and preload is not required, such as ordinary drilling machine spindles.

2. Angular contact ball bearings: This type of bearing can bear radial and axial loads at the same time. They need to be installed in pairs and can increase the stiffness of the spindle by preloading. There are many contact angles of angular contact ball bearings, such as 15°, 25°, 40°, etc., and each angle of bearing has its specific application scenario.

3. Double-direction thrust angular contact ball bearings: This type of bearing usually has a contact angle of 60° and is suitable for situations where bidirectional axial loads need to be borne. They are often used in combination with double-row cylindrical roller bearings and are used on the spindles of machine tools such as lathes, grinders, drilling machines, milling machines, and boring machines.

4. Double-row cylindrical roller bearings: This type of bearing can bear large radial loads and allow for higher speeds. They are often used on high-speed rotating machine tool spindles.

5. Tapered roller bearings: Tapered roller bearings also have high speed and load capacity, and can withstand radial and axial loads at the same time. If it is a double-row tapered roller bearing, it can also withstand bidirectional axial loads.

These bearing types have their own characteristics. According to the specific needs and performance requirements of the machine tool, you can choose the appropriate bearing type for use.