Notebook paper is remarkably consistent in thickness. This method takes advantage of this for setting tools. With this method you will place a piece of scrap paper on the finished face of the part and then jog the tool while spinning until it just contacts the paper. Contact of the tool with the paper is indicated when the paper begins spinning. The tool length offset is set to at position.
Begin by installing an end mill or face mill in the spindle. Follow all safety precautions. Start the spindle, and manually jogging the tool close to the top of the rough stock. Reduce the job increment to .001 inches per pulse and slowly move the tool down until it just contacts the face of the part. Then move the tool off to the side of the part and then lower the tool by the amount of the face cut (usually .005-.02 inches). Increase the jog increment to .01inches per pulse and move the tool in XY as necessary to create a flat surface on the face of the part.
Stop the spindle before proceeding! Jog the tool well out of the way so you do not bump it with your hand or head.
Tear a piece of common notebook paper larger than the diameter of the tool. Place the paper so it lies flat on the face of the part.
Follow all safety precautions to restart the spindle.
Manually jog the machine until the spindle is centered over the piece of paper.
Jog the tool close to the paper, and then reduce the job amount to .001 per pulse. Slowly jog the tool down .001 at a time until the tool just contacts the paper. The paper will usually begin spinning with the tool.
Stop the spindle but do not yet jog the machine.
Set the Tool Length Offset register at this value. This is done on the Haas by pressing the TOOL OFFSET MESUR button (beneath F1). Other machines may require you write down the Z-value reading on the CNC control and then enter this value in the tool length register for this tool.
If exact tolerances are required then the tool must be lowered by the thickness of the paper. Do this by ADDING the thickness of the paper (.003-.004 typical) to the Tool Length register.