I was doing an epoxy and wood project and needed to surface off the epoxy so I created a square and setup a surfacing operation to clean off the epoxy.
What I didn’t notice is that the surface job went a full bits with outside of the square I had defined for the operations, the bit was a 25mm surfacing bit.
Is this expected?
Below I have setup two operations, a Pocket at a 4mm depth with a 1/4” endmill, then I setup a surface operation with a 1mm depth using a 1” surfacing bit.
You can see the Surfacing operations goes far outside of the square I have defined.
I would have expected at least half the bit width for a full sweep. In your preview window, it sort of looks like this is what you would get. However, I cannot be sure. Can you add that .mage file to your Reply so we can investigate?
Did you actually run the file or was this based on the Preview window? Seeing that you did the Preview is a very good thing.
So here this was a bit more of a test below, I made the Surface and Pocket Square 100mmx100mm and then created a vbit Profile on the line going 1 mm deep for each ring out to 150mm.
You can see the 150, 140, and 130 lines but not the 110 or 120 so it would look like its doing a full bit width outside the surfacing box.
The reason I noticed is not on this included sample file but on a production file where are used the surfacing feature and ran right over my hold down, luckily for me they were 3D Printed so there was no issue.
I can see going over the bounding box slightly but a full bit width without a warning or option to reduce that might get people into trouble.
Surface Test.mage (9.5 KB)
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Re the step over yes this is normal with the surfacing operation
Yes I got caught out the 1st time I surfaced also, my own fault for not reading all of the docs thoroughly, who needs a manual right we know what we are doing 
Maybe this is something that could be looked at being added or changed at some stage
Thank you for highlighting that and I admit that I had missed or didn’t read that part in the manual about that toolpath.
But as you can see from the preview the bit was fully outside the box that defined the surface operation. The bit is 25mm wide and based on my real world use by accident and the preview I created it looks to be taking a full width pass outside of the desired box. So if the manual is saying half the width it’s not correct as far as I can tell.
@MillMage I can understand going over the bounding box but maybe similar to the profile operation it could be an option, inside box, half bit width over the line and full bit width over the line.
Something along those lines.
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Yes i see that , Im prob wrong but im picking it is becausse your project size is bigger than your design it will be something in the sufrace setup to cut past , one of the gurus will need to explain better than me
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I believe you may have to do an Inward Offset (half the surface bit diameter), of your Pocket shape.
That will correct for the pattern, but not correct the issue. If the Docs say centerline, then the path or the Docs need to be fixed. My money is on fixing the path. It appears to be a simple math error with the calculated path.
The Surfacing operation is intended for preparing the surface of your machine, and will run the center of the bit up to the line of your shape. You can draw a shape the whole size of your ‘accessible coordinate space’ and it will run the tool right up to that line.
The Pocket operation is intended to empty out a shape, and stay within the lines of that shape.
I just made one quickly, and you can see it doing what it’s supposed to. I used a 30 degree V bit to score the shape boundary first, then ran a Surfacing op, and you can see the bit clearly riding exactly along the shape boundary:
For contrast, here’s the Face op, the full bit diameter outside the boundary:
I loaded your file into my current development version and it looks like it’s doing exactly what it’s supposed to:
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The bit would go exactly half the diameter outside the shape, and you can see that’s exactly what it did.
This is your project, and this is half an inch from that corner:
Notice where the shape runs to (about halfway past the 3rd outer line):
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I should have waited for an answer.
So it is working as everyone thought it should. Next time, I will just mind my own business. 
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I edited that about half a dozen times - initial reply, then mocked up a file, then looked at his file, …
You’re good - you’re usually pretty accurate. 
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So correct me if I am wrong but my bit is 25.4mm wide and its going over 2.5 lines bacailly and each line is 10mm from the surface object shape. So it looks to be going outside the box by 25ish mm in this case and that is further than it should be going, correct?
I would have expected it to go about 13mm past the shape line.
Yes I used the Surfacing toolpath for this. I re-arranged the operations and added some more detail but the preview at least how I see it is going the full width of the bit outside.
Also how do you get the bit outline to show up? I also added the latest test file.
The reason I am asking is that I ran into my hold down clamps on a recent job and thought I had enough buffer on the stock.
Surface Test.mage (11.2 KB)
You’re wrong.
Your rectangles are 100, 110, 120, 130, and 140 mm wide. That means that the spacing on each side is 5mm, not 10mm.
The background grid squares at this zoom level are 10mm:
Your rectangles are spaced at exactly half that.
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LOL, wow yeah my bad for sure.
Maths, they be hard.
Thanks, sorry that took me so long.
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Coming from you, I am honored!!!
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