The positive cutter motion directions for a vertical spindle mill are to the right of the operator (X-axis), away from the operator (Y-axis), and up (Z-axis).

Horizontal spindle N/C mills are a little more confusing. For a sense of direction, one must be looking in the Z-minus direction, as if one's eye were stuck in the spindle and looking out at the workpiece. Then the positive cutting tool motion directions are to the right (X-axis), up (Y-axis), and toward the end of the spindle (Z-axis).

Paper method
Paper is cheap and easy to buy and are made very accurately to about .2 of a mm thick. There is more than one thickness available so check the thickness of the ones you are with a micrometer.

If a paper is wetted by placing it on the tongue it will stick to the side or top of a workpiece – if it is clean, that is, not oily. As the cutter approaches the paper it will suddenly snatch it. With care this can be done without marking the workpiece. But the cutter will then be within .2 mm thickness from the workpiece.

Of course, at this point, the axis of the spindle is half the width of the cutter away from the surface. (If edge finding)

If the (direction of rotation) DRO is set to zero and then moved in the right direction by half the width of the cutter and then set to zero again the reading on the DRO will be the distance of the reference edge from the axis of the spindle.

This method ca n be used to find all sides of the work, including the top of the workpiece.

An advantage of this method is that the cutter does not have to be removed from the spindle to do this

This is a superior form of sticky pin. It consists of a shaft with a ball joint at one end. It usually comes with several different arms that can be fitted to the ball joint. But the most commonly used end is another ball.

The wiggler will fit an ordinary collet chuck or drill chuck but it will not fit an Auto-lock chuck because it does not have the necessary screw thread on it.

The centre line of the shaft of the wiggler does not have to be very accurately aligned to the axis of the milling spindle to get good results. If the wiggler is rotating and the workpiece approaches it, the wiggler slowly straightens up. Then all of a sudden the wiggler flips completely out of line. The most reliable point that can be used for edge finding it just after it has flipped. Allowance has to be made for the diameter of the ball or whatever else is on the wiggler’s arm.

Once the wiggler flips it has actually gone past the edge. For the most accurate result, it is necessary to work out the position at which it starts to flip. This means making it flip a couple of times at least and noting the point just before the flip.

This is usually accurate enough for most work. however it is said that better accuracy can be achieved if instead of using fact that the tip flips at a certain point, this point is found by looking at the space between the surface and the wiggler with a bright light behind the gap.

This consists of two round parts held together by a spring. This is fitted in the spindle. The spindle rotates. If the two parts are offset as the workpiece approaches the bottom part, it tends to line up with the top. As soon as the workpiece goes beyond this point the bottom part jumps to one side.

One of easiest methods to find the centre of the shaft is to bring the cutter next to the shaft adjust make it touch the side of the shaft to find a reference face.  Adjust the table down so that the cutter clear the shaft.  Move the table on the Y axis by half the diameter of the shaft plus half the diameter (thickness) of the cutter