CERAMIC DISC TYPE ROTARY UNIONS
Ceramic disc type rotary unions are used in machine tool spindle applications of various makes, models and applications. This is a typical set up where one end mounts to the drawbar and one end mounts to the machine.
During use without through tool coolant the two discs are separated. When the coolant is turned on the pressure pushes the machine mounted disk forward until it contacts the disk on the drawbar.
If you look closely you can see the wear on the disk surfaces. This causes coolant to leak and potentially enter the spindle. This causes the bearings to be contaminated and eventually fail.
Check these surfaces every time you replace a spindle. Always replace the disks as a set. They wear together during use. Unmatched sets will fail prematurely. Follow the OEM installation and break in procedures.