CNC Services Northwest

Method 2: Use imaginary reference tool, use length offsets to locate part

Use this method if you have several tools you wish to set up, keep, and reuse; and you choose to set Z0 to a permanently fixed position (e.g. the face of the chuck or collet, or a headstock-mounted cutoff slide).



Preparation (one-time)

  1. Press TOOL CHECK to send the carriage to home.
  2. Go to the Part Setup screen (F1/Setup, F1/Part).
  3. Press F10 to set the Z axis part zero at home. Leave the tool number zero.
  4. Press F8 to select the X axis.
  5. Enter a Part Position of 4" (100mm) or more. Leave the tool number zero.
  6. Press F10 to set the X position (at home, with no tool offset) to the entered position. This will prevent the spindle from accelerating when going to tool changes with constant surface speed enabled.

Operation (for each job)

  1. Load all of the tools for the job into their tool holders.
  2. Load the stock in the spindle.
  3. Go to the Offset Library.
  4. Load a suitable tool and use manual spindle and jog controls to turn a true-running diameter on the end of the stock.
  5. Measure the turned diameter.
  6. Press F1 to set the X reference.
  7. Enter the measured diameter and press F10.
  8. Press the Right Arrow to move to the Z Offset column.
  9. Press F1 to set the Z Reference.
  10. Enter the Z coordinate of the end of the stock (usually zero).
  11. Press F10 to set Z reference to this coordinate.
  12. For each tool in the job:
    1. Load the tool.
    2. Highlight the tool's X Offset.
    3. Jog to touch off on the turned diameter.
    4. Press F2 to measure the X offset.
    5. Highlight the tool's Z Offset.
    6. Jog to touch off on the end of the stock.
    7. Press F2 to measure the Z offset.
  13. Press F10 to save the measured offsets.

If you have to replace one tool

  1. Go to the Offset Library
  2. Load and measure the new tool off the same surfaces you used before.
  3. If those surfaces are no longer available (e.g. have been machined away) then enter and set new Z and X References using surfaces with known dimensions; then measure the new tool off of these new Reference surfaces.


Rather than jogging until the tool actually touches the stock, you may want to use a spacer (e.g. feeler gage) as a go / no-go gage. In this case, simply add the thickness of the spacer to the Reference dimensions you enter. On the Z axis, simply add the thickness of the spacer. On the X axis, add twice the thickness of the spacer (because X dimensions represent part diameter, the spacer needs to be added to both sides).

For the most precise X offset measurements, you may want to turn a new, smaller reference diameter with every tool. If you do this, simply turn the diameter, then jog the Z axis until clear of the part. Do not move X yet. Measure the diameter; enter it as the X Reference diameter; highlight the tool's X offset; and press F2 to measure.

To measure the X offset of an ID tool or a tool mounted on the back side of the carriage (one which cuts from the X minus side of the part) you can either touch off or turn a diameter on the back of the stock, then enter the X Reference diameter as a negative diameter before measuring the tool; or you can hold a straight edge to the positive diameter (the surface you measured normal OD tools on), position the tool off the end of the stock, and jog to touch the back of the straight edge. This is less precise than turning a diameter on the minus side of the part, but is often quicker. A similar technique can be used to measure back facing tools off the front face of the stock.

Copyright © 2003 Marc Leonard
Last updated 31-Mar-2003 MBL