Bitsetter visited 3 times

It seems unnecessary but every time I use my Shapeoko, the router goes to bitsetter 3 times

  1. I switch on and initialise
  2. I open a file and click LOAD NEW TOOL as instructed in another post
  3. I start the job

Assuming a single tool job, surely only a single visit should ever be needed right before the carving starts

visit #1 (after homing) is mandatory, to establish a tool length baseline. The next bitsetter probing computes tool length offset based on this initial value

visit #2 is not necessary. The reason why we keep giving the advice to use the UI button to change the tool, is to cover the case of someone changing the tool WITHOUT using the button, and before starting a job: this messes up the tool length offset. The actual recommandation is “IF you ever need to swap the tool without being prompted to do so, do use the change tool button”.

So a normal workflow normally has two visits to the BitSetter.


The tool needs to be measured each time the machine has not had control over things.

As @Julien noted, it is not necessary to use the load tool button if one loads the desired tool either before powering up, or when prompted before the automatic measurement.

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The BitSetter is measuring any bit in the router and comparing it to the last time you set z zero. That last setting of z may have been the last time you used your machine last weekend. The x y & z settings are persistent over power cycles. If you manually change a router bit you break the calibration of the BitSetter. You recalibrate the BitSetter by setting the Z zero again. Then only change a bit when prompted or changing bit through software interface.

As Julien pointed out initialization is a set routine and will measure the bit automatically because the routine is hard coded in the controller firmware. When started by a job the gcode has the the commands embedded on it to ask for a tool and controller measure the bit relative to last z zero. This is baked into the gcode by the Shapeoko/Nomad post processor on CC.

Some small jobs with a single bit I just uncheck the BitSetter in config so I dont have to deal with BitSetter.


I think the BitZero V2 calculates the center of the spindle by touching off on two parallel end mill edges and this is inherently more accurate than BitZero V1, is that correct @WillAdams?

What I’m getting at is if one wanted to reduce the amount of BitSetting operations that are performed, you could…

  • Have your first cutter installed prior to initialization and home, BitSet, and zero with it (doing so with BitZero V2 versus V1 might be more accurate).
  • *Edit the gcode by removing the M6Txx command so the prompt for tool length measuring doesn’t occur.

…This would effectively remove BitSetter ops #2 and #3; but if you wanted the utmost accuracy then you’d want to probe zero X and Y with a gage pin and you’d have to use op #2.

Which CAD/CAM program are you using? @neilferreri has a wonderful F360 post processor that turns your project into an awesome one and allows toggling the first M6 command on/off. *I haven’t edited my non-F360 files to remove the M6 commands, but I think that’s all it takes to avoid the BitSetting at the start of a job, is that correct, Neil?


Whether or no the v2 is more accurate depends on:

  • whether on uses a probing pin or no (they help)
  • endmill geometry (the angle/arc at which flutes move around the endmill determines how close to the ideal perimeter)
  • depth relative to the BitZero the probing is done at (the v1 actually has an advantage here w/ its height)

They both work fine, and v1 can be nicer for folks who don’t want to use probing pins/don’t have a BitSetter, or who do jobs w/ a single compatible endmill, v2 is better for folks w/ a BitSetter, or who want to use arbitrary endmills.


Another difference is that the V2 triggers when a moving circular pin touches the inside of another bigger circle, which probably isn’t as reliable for large pin sizes as a circular pin touching a plane on edge of the V1.

V2 also requires the probe to push the BitZero in X and Y directions away from the corner overhang right angle, dislodging it, where as the V1 only pushes the BitZero body towards the ‘blocked’ path.

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