My Sl-10 tailstock on my haas has suddenly sprung a leak. It wasn't in use when I discovered this. I rarely use it. But today I went to use it, and when I step on the pedal to extend the quill, it moves for about 1.5 inches and then it suddenly stops movement. When the movement stops, that's when it also starts pouring hydraulic fluid out the back end of the cylinder. The back of this cylinder has a hole in it about 1/2 inch in diameter. I can't feel any threads in this hole, but it goes much deeper than the reach of my finger, so I don't know if I just lost a plug that goes in there or what. My knowledge of hydraulics is very limited.
The center (through) hole is for removing centers. On my SL-10, there is a hole through the sheet metal just above the chip auger that lines up with the tailstock. I use a rod to remove my live center.