I have 2 known R8 tools that for some reason were tapped about 0.1-0.2" shallow. Or perhaps the shank is a smidge too long. Either way its a potential headache. The draw bar bottoms out in the shank tool thread before the R8 taper is seated to the quill taper. This can actually become a real problem if you crank away on the drawbar without realizing whats going on. The guide pin in the spindle can get wedged in the R8 slot. So be aware of this with any new shanked new tool acquisition. Tighten it gently by hand the first time to ensure the tapered seat contacts the spindle seat properly. Pre-measuring the thread depth alone is not that meaningful because it could be the shank itself is a slightly incorrect length. While you are at it, check the thread condition or run a tap into it so it doesn't mess with your drawbar thread.
On to the fix. Not my idea, saw it on another forum. Choose an appropriate O-ring that is a snug-ish fit on the draw bar shank. Its job is to hold a steel spacer disc to the drawbar rod so it doesn't drop down into the bowels of the mill. The disc is turned to match OD of drawbar, ID drilled to clear the rod, counterbore recess the disc end so the O-ring fits inside. I made mine 0.275" thick but your mileage may vary.
On to the fix. Not my idea, saw it on another forum. Choose an appropriate O-ring that is a snug-ish fit on the draw bar shank. Its job is to hold a steel spacer disc to the drawbar rod so it doesn't drop down into the bowels of the mill. The disc is turned to match OD of drawbar, ID drilled to clear the rod, counterbore recess the disc end so the O-ring fits inside. I made mine 0.275" thick but your mileage may vary.
