"Clear all offsets" - do I need to?

I don’t understand what ‘clear all offsets’ does, even after reading what I could find about it here. Can someone clarify for me?

I have a Nomad 3 and I’m doing some prototyping now to set myself up for ongoing production of very small pieces. To save myself time and energy, I use the bottom left corner (the location the the machine rapid positions to) as my XY zero for everything, and just change the z-axis zero as needed. I’d never even noticed the ‘clear all offsets’ until I made a minor goof in my work today, but now I’m wondering if it’s something I need. I’m working on very small pieces with tight tolerances, so I want to make sure I’m doing everything I can to maintain the machine’s precision.

“Clear all offsets” just makes your work co-ordinates the same as the Machine co-ordinates.

When you set a zero, what’s happening internally is that GRBL records the machine co-ordinates for that location, then adds those values (the “offsets”) to the GCode co-ordinates to get the desired machine location. “Clear all offsets” just sets those values to zero.

The only time you would use it is if for some reason you had a GCode file that used machine co-ordinates. It’s likely not something you will ever run into.


or setting up a bit setter on a ShapeOko :slight_smile:

Does “Clear All Offsets” also clear the offsets for the bitsetter and tool length?
Or just the workpiece coordinates?

I will agree that this is a little confusing…well it STILL is for me.

At present I have 3 active setups on my Shapeoko 3. 1) Prep the bar stock for my 4th axis (Vise), 2) Mill the mini rods (for my 1/5 Scale Briggs and Straton Engine (4th Axis)), 3) Drill the end caps and rods for the 0-80 threads (back to the vise but in a different location IN the vise).

One would think you could just home the machine, clear offsets, and then jog over to your and set the next X0Y0. When you send the machine home again to check the XYZ locations,($h) you’ll notice that you are off on the X and Y by 0.118" (3mm) the “pull off” amount. So I need to: Home, Clear all Offsets, THEN click, Zero All (makes no sense), then jog to my preset coordinates. Then and only then are the settings correct. Odd fact, when I set my first setup, I didn’t need to Zero after homing, but I do need to clear them for the additional setups…things that make me go hmmm.

Mine is Not to reason why, but to do…

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You should not need to zero after homing. The home position is G53 X-0.118 Y-0.118 Z-0.118
This keeps it from bumping the limits when you go home.

The “Set Zero” sets the offset from machine zero to the work coordinate (G54)

If you zero at the home position, then zero at your workpiece you are overwriting the first zero.

If you’re using CM, the 9 preset positions, home position, toolchange position and bitsetter positions are stored in machine coordinates. I’m not sure why I would ever use “Clear Offsets” unless I’m
doing something new relative to machine coordinates. Moving the bitsetter. Maybe surfacing the spoilboard??

Yeah I know what I SHOULD need to DO but what I am telling you is what I HAVE to do to get the (multiple) coordinates to repeat. Like I said…seems wrong…but…

I miss the old days of using G54, G55, G56, etc…that made so much more sense.

giggle…my spoilboard is flat within 0.001" over a 14" x 14" work area.

To me honext, its not a spoilboard…but a metal work surface…machinist do NOT cut into the table, or work surface.


I read your explanation as expecting to see 0,0,0 when you went to home.
If I send the machine home & clear offsets, I expect to see X-0.118 Y-0.118 Z-0.118.

So you’re clearing offsets so you can move to the next preset coordinates relative to machine zero.
That makes sense. How are you setting & moving to the next preset coordinate?

If what I read is true, GRBL does support G54-G59. But the “Set Zero” buttons in CM only set them for G54. You would have to set them for G55-G59 manually. (G10 L2 or G10 L20)

Did you know that GRBL (ver 0.9) used to support G54-G59. Used it for years when I first bought my Shapeoko back in 2015.

Let’s stop killing a dead horse…Amost nobody uses multiple setups on the machine all the time, like me… Trust me, something is wrong, but I have a work around.

Move? MDI

I’m getting the sense from reading through this and other posts that there’s a difference between the shapeoko and the Nomad - the clear all offsets is irrelevant to me, but that shapeoko owners may need it. I still don’t understand why, nor do I understand what it means or how it differs from setting zero.

Here’s what I DO understand, and where it breaks down:
-GRBL is akin to an operating system for the machine(?). No idea what it is beyond that.
-No idea what G54-G59 means, except that I think G54 has something to do with the home position
-“Machine coordinates” means…where the machine actually is in physical space?
-Work coordinates/zero give the machine a point of reference, which allows you to put your stock wherever you want on the bed and still get an accurate cut. This is the part I understand best, at least from a practical “what does this mean for me, doing my work” standpoint
-How does the machine remain consistent in knowing exactly where it is in physical space and returning repeatedly to that point? How are there not mechanical/environmental issues that lead the machine to ‘drift’ away from where the computer thinks it is? My assumption going into this what that THIS is the issue that ‘clear all offsets’ resolves, but a) I’m not sure if that’s right and b) I still have no idea HOW it would do that.

At this point I’m clearly going well beyond what I actually need to do that jobs I need to do. I apparently don’t need to know what this button does, I don’t need to use it, and I could just leave it at that. Seems to be plenty accurate enough for my needs. But it bugs me that I don’t understand so much of what I see talked about in this forum, given that this machine is so vital to me right now.

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If you move to cncjs you can use g54-g59 work coordinate systems. I find them incredibly useful, but it annoys me that if I’m working in e.g. g59, sender automatically goes back to g54 after finished operation.

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I tried It. Hated it due to the lack of support (knowledge base) for installing a 4 axis. Now I use two OS. CM for my 3 axis. USB to index my 4th. Works well for me.

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