I'd be careful and take a look at how far out the spindle moves out before it comes right off the thread. You don't really want it hanging out that far, and by the sound of your description, you may be doing just that.
Use a stubby spotting drill or a center drill to start the hole in the end of the workpiece. Don't expect to start a flimsy drillbit in the end of a piece without an accurately placed start mark.
The end of the part also needs to be faced square before you attempt to drill into the end of it, or it will force the drill to wander off. You might be surprised that even on a large lathe, relatively small details like this will flex a 3" diameter spindle.
Another thing to look at is the accuracy with which you are chucking the part. If the start dimple is off center because your chuck is no good, then the drill will wobble as it attempts to follow that dimple, and flexure of the tailstock will ensue.
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(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management) |