Coolant-Seals

High-pressure coolant seals are the weak link in every deep hole drilling machine. They operate at the boundary between rotating and stationary components, exposed to abrasive coolant, high pressure, and continuous wear. I have seen seal failures cause coolant leaks that damaged spindle bearings, contaminated gearboxes, and flooded machine enclosures. A single seal failure at the wrong time can cost $15,000 in repairs and three days of downtime. Where Seals Are Used The primary seal locations in a deep hole drilling machine are the rotating union (coolant inducer), the spindle draw tube connections, the coolant pump shaft seal, and the high-pressure hose fittings. Each location has different operating conditions and requires a different seal type. ...

Seals in a deep hole drilling machine don’t get much attention — until they start leaking. Then they stop production and cost time and money to replace. I’ve dealt with seal failures on both gun drilling and BTA machines. The symptoms range from annoying drips to complete coolant system failure. Where Seals Are Used Deep hole drilling machines have seals at several points: Rotating coolant union. Where the coolant transfers from the stationary supply line to the rotating spindle. This is the most common seal failure point. Drill tube connection. Where the drill tube connects to the spindle. The seal here prevents high-pressure coolant from leaking around the connection. Pressure head. Where the coolant enters the bore at the workpiece entry. The pressure head seal contains the coolant and directs it into the bore. Cylinder seals. On machines with hydraulic feed systems, the cylinder seals keep the hydraulic fluid contained. Each of these seals operates under different conditions — pressure, speed, and temperature vary depending on the location. ...