Hey Bill,
one simple way to verify X/Y-squareness of the machine is taking a workpiece nearly as big as the workarea, fixing it at marked points to ensure repeatability, then program four holes that form an exact square to be milled in the outer corners of the workpiece, milling them, and then rotating the workpiece by 90° and repeat the program. Et voilà.
It simpler than the tiled cut example which also shows if the machine has un-squareness.
See also this for stitching instead of milling.
Yes, I did sin and mix the units. 
I have a 4" vise jaw and swept about 3" of it, but the indicator is in mm since I try to standardize on that unit.
I like the idea that homing is the culprit here, since that means I’ll have a much easier time fixing this.
That’s a great idea and should be relatively easy to setup. Thanks!
I’m still having a hard time picturing why measuring outer corners of the feet is better than say, mounting an indicator and sweeping a vise or fixture plate. Is there something I’m missing or is this a different measurement than squareness?
I’m ~80% sure this is out of square, though it could also still be a parallelogram. Here’s one example piece I tested yesterday where the tilt is most obvious visually. I did cut a square test pocket and visually it has a similar tilt to it. The pocket is roughly equal on the diagonals and flats according to my quick check with some calipers.
Are you talking about X/Y squareness or X/Z squareness?
Anyway if you want an angle to be 90° (=if you want your machine to be X/Y-squared), then you measure X and you measure Y and then, with knowing the angle you want (90°), you compute the diagonal that has to be there. Then you check by measuring the diagonal.
Remember that if one diagonal is shorter than the computed value, the other will necessarily be longer. So to ensure a 90° angle, it will be enough to shift one axes’ ends until the diagonals are identical.
One simple way to ensure squareness of X to Y on the machine is ensure by measuring that both diagonals are identical. It’s as simple than that.
At first sight, this looks as if the letters are rotated in comparison to the rectangle.
If we have rotation here, then it is not a X/Y out of square issue.
Do I understand it right, you milled the letters, or the shape of the rectangle or both or what?
I’m not sure if I get what you mean. Could you describe where you put the probe of your indicator and what is the reference point?
Here’s what I used on mine. Works great! At 20mm long, they are just about 1mm longer than the .750" bearing stick-out (look at me, mixing mm & inch in the same reference. 
)
All you need now is to replace the . with a , and it will be like every engineering project with a globally disperse team I’ve worked on 
I’m assuming you mill the text on an existing rectangle stock.
Could it be that the stock was not set square to the machine?
Hey eaststreetcarry,
if your machine is a parallelogram, i.e. if the angle between X and Y is no right angle, then the X axis will have a tendency to square itself during movement over the Y axes. But if Y steppers are stall homed and the machine has X and Y not in right angle, one of the Y gantry blocks will reach home before the other (remember, even if buildbotics controller is prepared for driving the two Y steppers with one single driver, on Onefinity CNC each Y stepper has its own driver and control). The question is, if one Y stepper reaches stall homing, will the controller stop the other Y stepper then or will it stall home independently, after the other? If yes, then Y stall homing will “twist” the X Axe then in order to reach stall home on both Y steppers.
In every case the first thing I would look at, is if your machine really has right angle between X and Y.
@eaststreetcarry
All is not lost, okay I went down this rabbit hole a months ago.
On side not, to me it looks like your stock was just not in squarely or your reference line was off. 
Doesn’t mean you don’t have a square ness issue. I recommend putting down a large test piece. Trace the boundary, carving a fine line, then put a large square to it.
That’s exactly what I had in mind with my previous pic.
X/Y squareness.
Ah, okay. I’m assuming the machine itself is square and the relation between the machine and the work is “out of square.” I’m also a n00b with this, so take whatever I say with a grain of salt.
The letters are not rotated, the entire toolpath is rotated. This is a pre-cut plaque and then I did the engraving for the letters.
The stock is in a vise on a fixture plate which also has the machine bolted on it, so the machine and the fixture plate are “out of square” I think. This is the same as the stock not being square to the machine.
How about some pictures of your setup?
You could draw a 3,4,5 triangle and check it for square and true to the bed of the machine? just a thought. or 6",8",10" or ratio there of.
Something like this…
Hey Tom, hey Steven (@sdramer),
sure, that’s what it is. Geometry, instead of Comparing to a Reference Body.
But I find that like many youtube videos, it could be much shorter and denser.
…And if you specifically take the onefinity cnc with its four feet that one wants to put on a table top (i.e. a flat surface), it is much simplier. You wouldn’t even need a meter, just a stick which, by putting marks on it, allows to compare two measures: The one diagonal and the other diagonal, measured like in picture above.(1) When the diagonals are equal, it’s “squared”. The diagonals in a parallelogram differ, the ones in a rectangle don’t.
1.) But you are right, if you measure at the feet, you must be sure that the rail above is at a defined position relative to the foot
If instead, like in the video, you measure at the points where your bit drills a hole or your needle stitches the cardboard, you are the safest. That’s what I’m taking into account with this other method.
I have the same suspicions about my setup as well. I just cut all the holes for my threaded wasteboard, marked reference lines on the table so i could reinstall the wasteboard in the exact position. When I reinstalled it, I moved the bit into a hole in one corner and ran the machine across X to the other side and the bit was about 1/4" off the opposite hole. Kind of of bummer I didn’t somehow check this before hand. I was able to line up my holes running along Y for now. I will try and post some pictures.
I did notice when the machine is homed that the right Y rail stops just a bit before the left side. Lots of good advice and content here for me to try and nail down the issue so I will run through some tests mentioned here. Thanks all for the help!
Many of of us have been there…
I hear you on this point, but consider this.
If the instruction is too drawn out for your level of knowledge you can fast forward and jump to the juicy parts. I have used the right arrow key to jump 5 seconds at a time and skim through sections that I think I know well enough to do so. But later occasionally found myself in full reverse because I missed some critical tidbit of info. DOH!
OTOH, if the video was only a highlight reel, then those who need a little more detail to grasp the information cannot hit the slo-mo button and get that extra detail they need.
Hey Bob,
I’m learning everyday, didn’t know that this is a new word in english. In Germany most movies and series are usually dubbed and here Homer says “Neinn!”
