I had a friend over last night and we managed to get the machine pretty square, so I thought I’d share some of the techniques we used last night.
Here’s the machine, with A-B being at the front, C-D at the back, and your Y rails running from A-C and B-D
C----D | | | | A----B
First, make sure that the A-B distance is the same as the C-D distance. Be as accurate as you can, it will pay off later. Once you have them the same distance apart, make note of the measurement.
Now measure your diagonals. Most likely, they’re not going to match up. Let’s focus on the shorter of the two measurements.
If A-D is shorter, you need to move A away from D, so what you need to do is move A and B to the left. And if B-C is shorter, you need to move A and B to the right.
Now that you know the direction you need to move, start by moving A in that direction. Then, using the A-B/C-D measurement you took note of earlier, adjust B accordingly.
Once you have A-B = C-D and A-D = B-C, you’re square!