Advanced newbie question

Brand new user. Just got my machine up and running and cut my wasteboard.

However, subsequent cuts set to material thickness are cutting into my wasteboard. I think my Z axis travel is off.

I got a dial indicator like the one Winston Moy talks about in:

…and I’m trying to learn how to set it up and use it.

At about the 8 minute mark he talks about making an adjustment to the Z axis, but does not say HOW.

I’ve also seen:

Which talks about the math required, and says “…enter (it) into Grbl…”
So I get we need to make the changes in Grbl once we figure out how much things need changed…

But is there a Shapeoko “how to” article somewhere on how to update the settings on Grbl? Because if there is one I haven’t found it yet.

I found one for X-Carve, but I don’t know if the steps would be the same.

Thanks for the help!

Looks like you’re all over it with the guides and information, nice work on hunting it down (far better than I did when mine was new)

A common reason for cutting into the wasteboard is innacuracy in measuring your material thickness, or when you set your Z-Zero, it is too low/digging into the material.

If I were you, my way forward would be:

  • set your dial indicator up so you have the base sitting on your wasteboard, very securely, with the measuring point sitting on top of your router/spindle mount (remove your router/spindle to make it easy) then in the jogging selection set your increments to any number you can measure on your dial indicator (I use 0.1mm, then 0.5mm, then 1mm) then jog the Z up and down one increment at a time to confirm the axis is moving the correct amount.
    You can adjust your $100, $101, $102 figures to change how far the stepper moves per commanded measurement. - Check here for a guide


  • Try a few jobs setting your Z zero to the wasteboard (in Carbide Create/Vcarve), this way your material thickness measurement can be off by a little and you won’t cut into your wasteboard

In addition to @stutaylo’s answer, my take on the belt stretch calibration thing is here, but if I understand correctly one of your questions is more around how to change a parameter in GRBL ?

You can modify GRBL parameters using the MDI console in Carbide Motion:

go to the “Settings” page, click “Open Log”
then go to the “MDI” page, and you have a prompt there where you can type in $ commands, for example to type in the calibrated Z steps per mm you derived from the dial indicator test, for example


then click Send. Then send “$$” command and check in the log window that your new $102 value has been taken into account. Things scroll by continuously in that windows, it’s a major pain in the neck. Later you can use another G-code sender that makes this much easier :slight_smile:

But as @stutaylo also said, it may not be a problem with the Z calibration, which is typically more than good enough by default at 40 steps/mm, more likely an issue in setting zero or uneven stock thickness. Definitely never trust the rated thickness for any material, use a caliper to double-check it yourself. By how much do you cut in the wasteboard ? If it’s by more than say 0.02", probably not a Z calibration problem.


I think that before you start playing with the GRBL settings, I would check your work setup. Is the wasteboard flat? Is the workpiece sitting flat on the wasteboard? Is the workpiece flat?

An easy way to check overall flatness is by setting zero on your work piece using a feeler gauge then move the spindle to another location on some kind of a grid using the jog command let’s say 100mm then move the Z to Z+6 in rapid and move down from there to Z 0 with the last portion using .1mm steps. You can see if you get to 0 value at that location. Mark your findings on a graph paper then move to the next location.

You may find right away that the workpiece is not flat or sitting flat on the wasteboard.

also personally I rather cut a little bit (0.01" or so) into the wasteboard than 0.01" too little and having to clean up the work piece with a saw and sanding etc

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Thanks for all the replies!

And Julien, that’s a great page on dimensional accuracy you linked. I’ll dig into that.

Fortunately I think I have I found my problem before going down the rabbit hole of Grbl settings. I was gathering info to clarify my post…

I’m using MDF (standard .750 thickness) and the touch probe for probing x/y/z. I’m using a file pulled off the internet to create clamps, so I figured all settings should be right.

The cutting depth in the file off the internet is 0.760.

ugh… newbie mistake. I should have checked the file settings before running the job.

I’m making sure I post this as a follow-up so that others will see it and learn from my mistake. Always double-check parameters on files you download… especially when you are new at this. I was about to spend hours chasing Grbl settings, when it looks like it was just cutting parameters.

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I think that .760 was deliberate by the designer in order to ensure that it cuts through and you ensure that don’t have to go to the bandsaw to finish the job. It is always a good idea that you go through the settings on a project that was designed by someone else or even a project that you may have done some time ago to ensure you have no surprises.


Definitely deliberate (was it the Myers wasterboard maybe ? I seem to remember this 0.760 value from somewhere).

There are two kinds of people: those who use their wasteboard as a wasteboard (i.e. overcut on purpose for the reason you mention Luc) and those who feel good when they have set they cut parameters (and squared/trammed their machine) JUST right so that the cut ends up barely scratching the top of the wasteboard, while still cutting completely through the piece. To each their own :slight_smile:

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lol… you all are exactly right. And I guess I’m looking at it like: “why spend all this time getting things straight and flat just to cut into them and make the surface uneven?”

That being said, I just did my depth settings to “stock bottom” on MDF and it still cut a small amount into the wasteboard.

I’m going to try and run an initial flattening on the wasteboard later today and then run another job and see how it goes.


Are you using a supplemental wasteboard on top of the structural one?

You can also set your zero based on your wasteboard rather than the top of your stock. Let’s say your cuts are to go 15.2mm deep (stock thickness =15.2mm). You could jog to your newly surfaced wasteboard, or a couple 10ths of a mm above, and send G10L20P1Z-15.2. That sets your wasteboard surface as the maximum depth of cut. If you cut beyond that, your problem is mechanical.



Yes, I’m using a supplemental wasteboard on top of the structural.

That sounds interesting… could I z-probe the wasteboard to somehow set that bottom limit? I’m going to be cutting stuff with lots of different thicknesses.

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Only if you’re using CAM software that allows you to zero at the bottom of the stock.
I don’t use Create or Motion regularly. Whenever I’m doing a cut all the way through, I always use my wasteboard as the reference. A piece of 3/4" maple will vary in thickness and flatness, but the bottom of it is always on my wasteboard. If I set the thickness in my CAD/CAM as 20mm, and I set my wasteboard at Z-20mm, I always cut through. I usually use tape and superglue, and the tape thickness is plenty to protect the wasteboard from scarring. That said, cutting through and into the wasteboard is actually usefull sometimes. Just deal with it and resurface / replace the sac board as needed.
Like I said above , though, if you tell the machine that the wasteboard surface is -15.2mm and your max depth is 15.2mm, but you’re still cutting into the wasteboard, you have a mechanical problem with your Z.


I searched for a list of g-codes. I found a list. But the list does not show the G10. In fact it has several code missing. Where can one find a complete list of code that the Shapeoko 3D excepts?
Speaking of waste boards. Has any body thought of putting the thread inserts in the main board. That way you only need holes in the real waste board. When it is time to replace the waste board just cut new holes. No need to remove all of the threaded inserts and move them. Or would this damage the Shapeoko 3D?

The G-Codes which are supported by Grbl are listed at:

(incl. G10)

Note that some of those will be disallowed by Carbide Motion and in order to send them you will have to preface them with a slash — please use caution using such commands — in particular, some work coordinates are used by CM to track machine positions.

Best practice is to use such commands with a 3rd party tool, and to resend the machine defaults again before using CM:

You may find and

of interest.

Ok, I figured out my Z axis was not traveling far enough per movement.

For example, I pulled the Myers XXL fence file off the internet, loaded up some ¾ MDF, set the cutting depth to Stock, and used the probe to find X, Y, and Z.
The parts ended up not being cut out at the bottom. Measuring with calipers showed a remaining thickness of .040 inches.

I’ve done the math and set the Grbl settings. I think I have everything set right, but I went to test it with the dial indicator and I seem to be getting different spacing in my steps.

My dial indicator is in inches. My Carbide Motion is set to inches, and .01 per step.

My dial indicator is touching the router mount, so it’s not on something that would flex.

Take a look at the following video. Sometimes my steps are exactly 1/10th, and sometimes more or less. It averages out, but on some rotations of the dial up or down, some of steps seem way off to me.

Is this normal and my measuring method is off? Or do I have some other problem going on here?

did you check if the tiny m3 set screws that secure the sprocket onto the motor axis for your Z are tight? I’ve had those come lose a bit after a crash and then they slip very very occasionally

That happens due to 1/40th of a mm (the smallest step which the machine can make unadjusted) not evenly dividing into 1/10th of an inch once one adjusts this.

Measure over the largest distance possible to reduce that affect, or pick a number which does match some number of whole steps on the part of the machine, or just calibrate each piece you cut with a test cut each time, or work up a spreadsheet which measures every possible step position and the actual movement of the machine.

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