Dumb zero question

Ok, so I get that I can set my zero to my work piece. That its arbitrary etc.

My question is, where on the bit is it zeroing to. Is it the center of the bit? Should I be zeroing to the tip or should I put the edges on the edges of the x and y axis?

This makes a difference when doing a 1/4 to 1/8 bit change. Would mean I can’t use the “use last home” button. And might explain an issue I foresee before it happens. Lol

Thanks all

Should be center.

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Yes as TonyNo said, zeroing always happens to the center of the bit. It doesnt matter the size of the bit when setting zero as the gcode program will take into account the bit size and adjust moves accordingly. Always set zero from a center point so that you can repeat it if you need to make a tool change. Also, if you have your steppers to stay locked all the time, you can simply change the bit out and then reset your z axis zero and continue on your merry way.

The problem i found, in my one attempt, was if the axis are locked is the bit wont come out… I guess i could always have a higher safe clearance right?

X 0 and Y 0 use the center of the bit. So if you were using a 1/4 bit to set you would just touch the material at X set 0 then move up and over 1/2 the diameter of the bit. In this case .125" and then set X 0 one more time. Next you move so you can put the edge of the bit up against the material in the Y axis and set Y 0 now raise the bit again and move 1/2 the bit diameter and set Y 0 again. Now if you move to X 0 and Y 0 the center of the bit will be at the exact corner of the material.

Now move the bit so it is over the material. Using a feeler gauge of a known thickness lower the bit slowly until you just feel pressure on the feeler gauge but can slide it back and forth under the bit. Set Z 0 now mover the bit off the material and lower the bit to 0. Then move the bit the thickness of the feeler gauge and set Z 0 one more time. the end of the bit is now at Z 0. If you now move to X 0 Y 0 Z 0 the bit will be centered on the corner of the material and will be just touching the material.

Normally you should be able to move your Z up for a tool change and if you have a way to set the tool to the same length as the tool before it then your Z 0 will not move.

In easel it locks that one as well.

Yes with the machine powered up and reset so steppers are powered you of course should not be able to move an axis manually. All axis moves should be done from your control program. If you get to a tool change in the Gcode you are running for a part and can not jog the Z axis up to give you enough clearance to make the tool change and if the control software does not return to where is should be after the tool change then the control software has a big problem.
Good control software such as LinuxCNC or Mach 3 or 4 has the ability to move to a tool change position when the Gcode calls for a tool change. It also has the ability to measure the tool length of the new tool on machines that do not have repeatable tool holder that you can set the tool length and when the control software calls for a tool change it will automaticly adjust for the new tool and when you hit go again it will move to where it needs to start the cut for that new tool and will not cut deeper or shallow.

If the control program you are using does not do this and you need to make parts that require multi tools to complete then it may be time to investigate new control software.


It would be nice if Easel could unlock Z for this. :wink:

I don’t understand what you mean. “It would be nice if Easel could unlock Z for this.” Are you saying that during a tool change that you are not able to use the jog controls of the software to move the Z axis up.

If this is the case then the developers of Easel need to address this problem and fix it. If you can not move the spindle where you need it for a tool change this is a big problem.


Tony, is there a reason you don’t want to use the jog controls to move the Z up for the tool change?

Yes, seems easier to do it by hand, especially since my x-carve is “around the corner” from my PC. Mainly the first bit. Note that I added a crank handle to my Z.

Does the turn crank help if the motors are locked?

Sure, just as much as the gas pedal in your car when you have the brakes on. :wink: That’s why I’d like to see the option of disabling Z (or any other axis, selectively).

The alternative is support for Z probing. :smiley: That should come when they let us send G-code from Easel, if not before.

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If you do what you are thinking you will loose your reference and the software no longer knows where the machine is at. It is the same as loosing steps when the machine is running and something causes an axis to bind and the steppers loose steps.

CNC machines are not meant to have an axis moved by hand once the machine has been homed or referenced.


Currently, I turn off power and try not to move X and Y, just redo Z zero. No real issues so far. Killing Z alone would be better.

Sorry for this question, but: Is there a tutorial on how to Zero the machine propertly, inventables way? (the default way, no mods or things like that). I’ve been looking for info but didn’t found a lot.
You should just push the spindle in X, Y, Z manually? Does the machine have to be on or off when doing it… basic stuff like that. All the dos and don’ts.