BitZero and Bit Changes

This has been asked before, but I can’t find a clear answer. After using BitZero with the dowel pin, you change the pin out for an actual fluted bit. How does that not screw up the z-index zero point? The bit is potentially a different length than the dowel pin and the tips of the bit and pin are at different distances from the collet. The answer is typically, ‘Trust the machine to know the tool has been changed.’ I’d like to understand how the Z-point doesn’t get screwed up when changing bits.

This only works if one has a BitSetter which is then used to measure the tool length offset of the new tool.

If you only have a BitZero, after changing a tool you must re-zero the Z-axis, see:

I have both BitZero and BitSetter. So is this workflow correct?

  1. Install dowel pin
  2. Ensure BitSetter in enabled in software
  3. Zero XYZ using BitZero
  4. Change tool/bit.
  5. Load program - BitSetter kicks in automatically and re-zeros Z and cutting starts
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Please instead use:

  • power up machine
  • begin initializing machine — it will home and move to the front center and request a tool
  • install probing pin
  • BitSetter will measure probing pin to determine initial offset
  • Zero XYZ using BitZero at a corner
  • load file
  • run file
  • program will prompt for a tool
  • change to correct tool
  • allow BitSetter to measure new tool

Only interact w/ the machine, changing tool when prompted.


Never change a tool manually without being prompted either by the gcode or using the “Change Tool” button in the CM interface. Manually changing a tool without being prompted to will cause the BitSetter and Z zero to be out of calibration with each other.

The BitSetter is only comparing the tool in the router with the last time the Z was manually set either with the paper method or the BitZero. Changing a tool without being prompted causes the Z zero to be lost. So when you power up and initialize the BitSetter is comparing the tool to the last time you set zero on Z which might have been the last time you used the Shapeoko.

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