You drill to the depth of your quill in your tailstock, then you stop the lathe, retract the quill, unlock the tailstock, move it forward into the hole, lock the tailstock down, then turn on the lathe and drill to the depth of the quill in the tailstock again.
Repeat till you are at the necessary depth. If you try and move the tailstock with the crossslide, you will have a very inaccurate and wobbly hole.
Wade |