Newbie - Squaring issues

Came to the last step of the assembly which was squaring. Pulled the gantry to the front where the y-axis plates were touching the base plates, and tightened the screws on the base plates and y-axis rails. When I started the process of tightening the gantry to the y axis plates in an x-pattern, the gantry plate on the bottom left pulled away from the base frame by a little bit. When I pushed the gantry to the opposite end, there was a similar gap in the opposite corner.

This makes me think that the 2 y-axis rails are at least parallel, but that the overall shape is slightly parallelogram-ish. Is this a problem?

I watched one setup video where the guy actually clamped the y-axis plates to the base plate while tightening all the screws but didn’t know if that was advisable.

Any thoughts?

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The machine will run parallel to itself along the parallelogram, but if you want circles to be circles, and squares to be squares, you’ll want to do better.

There’s a bit on the wiki: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable including the official instructions which I’m pasting in below:

Squaring Gantry to Front/Rear Plates

  • Loosen all of the screws that hold the gantry together (4 on each side), these should still be loose from the initial assembly.
  • Loosen the screws that hold the Y axis rails in place (16 total). These should also still be loose from the initial assembly.
  • Slide the gantry to the front, so both Y plates are touching the front plate.
  • While holding the gantry against the front of the machine tighten the front of the Y rails (8 total)
  • Now - systematically begin tightening the 8 bolts on the gantry. Work your way from left to right, going back and forth in a X pattern (similar to tightening the wheel of a car).
  • After the gantry has been secured, slide the gantry to the rear of the machine and tighten the 8 screws while keeping the gantry pressed against the rear plate
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So step 5 is where the y plate on the left stopped touching the front plate. Do I just clamp the plates together while tightening the screws and repeat on the rear of the machine?

Sounds like a good technique to try! Let us know how it works out. Due to manufacturing tolerances it seems to be a bit different what’s involved in squaring up each machine (personal inclinations of the people doing the work may play a factor as well). My inclination is to just document everything everyone does successfully and people reading can make up their own mind on what’s appropriate for them to try.

So I had some time to start troubleshooting the square issue. I measured the distance between y-rails at both ends, and they were the same. But when I tried to determine if the x-rail was square to both y rails, it was square to the right y-rail, but very slightly off form the left y-rail.

Is that even possible if the y-rails are parallel to each other since the ends are equidistant? I know it’s not square because I ran a small test cutting out a circle (plug) and another circle (hole) and ended up with a slight ellipse.

Think I’ll try the clamping approach tonight to see if that works. Any other tips for making sure the x-rail is square to the y-rail. It’s harder than I thought because the plates get in the way.

Thanks for responding.

Also, I’m assuming I need to make sure the base plate screws are loose while I do my squaring?

Yes, loosen all the frame / structure screws, then tighten them so long as they don’t pull the frame out of square — if need be, secure it against that (clamps), or add shims if necessary.

Just as a note - there is an angular tolerance in how square the ends of the rails are cut.

My (and other people’s) rails have not been completely square on the ends. You can fix this with a good square and some careful filing.

Or if you have a friend with a mill they can mill the ends square for you.

You could also just put shims (cut up soda cans work well) between the end of the rail and the end plate to square things up.

If the ends of the rails are not square to the end plates then you will never get the machine 100% squared up.


I’m a newbie too. I had this exact same issue last week. Re-read the assembly instructions and noticed I had missed loosening the screws on the gantry (x-axis rail). Previous to fixing, I was just loosening one rail end at a time. I loosened all the screws on both ends of all 3 rails (24 screws in total). Then grabbed all the rails with both hands and rocked them back and forth several times. Tightened all screws slowly, and alternating like tightening tire lug nuts. Was much improved. I just did “hello world” last night, so I still have a ways to go, but this definitely improved my “squaring” issue dramatically and to the point where I felt like it was fixed.


Same Problem (kinda solved) (so far). Gantry had a 1/16" gap on one side. Fortunately the gap was on the left on the front (when gantry full forward), and on the right in the back (gantry full aft). So skewed like a parallelogram… Tried everything, until now… I think I got it.

Now… (Here is my approach)(worked so far)
Took most of the Shapeoko 3 apart.
Loosened “ALL BOLTS” (That’s the wasteboard, Y Rail, X Rail, all…)
-Found a large piece of glass for the Shapeoko 3 to rest on (level surface).
-Replaced all bolts with longer bolts, washers, spring washers, and nuts to allow easy tightening (I tighten nut, not bolt. Like a stud) (this is not necessary. But I do recommend the spring washers).

-Big step here… LOOSEN THE V PULLEYS! (8 V-pulleys allow the gantry to slide fwd and aft) (loosen them all) .

  • Slide the Gantry all the way forward.
    -Look for a gap
    -If there is a gap … Big step here… Pick up the front of the Shapeoko 3 by the frame :wink: twist the frame base left or right to fix the gap (imagine you are straightening a parallelogram). Check the gap. Continue to adjust the main frame left or right from the front lowest points.
    -Once gaps are resolved, tighten the front main rails only ( the 8 bolts facing you). While holding the gantry forward touching the forward frame - Tighten one bolt on the left, then the opposite one on the right. Then left, then right… Till all 8 are snug.
    -Tighten X-Rail bolts (left and right) (8 bolts) one on the left, then opposite one on the right, back and forth, while keeping the gantry tight against the forward frame.
    -Tighten the aft main rail bolts (8 bolts). left, right, one at a time swapping sides…
    -NOW tighten the V-pulleys…

Just to clarify - Tighten in this order (1 fwd Mains, then 2 Gantry, then 3 rear Mains):

3-------3 aft main rails 4 bolts a side (8 total).
2-------2 gantry, 4 each side (8 total).
1-------1 fwd main rails 4 bolts a side (8 total).

Slide gantry aft. Check for gap. I did not have a gap, so I don’t have any suggestions if you do.

Now, I am going to reassemble the Shapeoko 3. Once assembled, I will repeat these steps.

NOTE: If you cannot fix the gap with the above steps, try rotating the X-rail upside down (they are mirrored). look for the gap. If that doesn’t work, try flipping the main rails upside down, maybe swap sides… Look for gap.

I will post when complete with final results…


I have already solved this kind of problem once but I have it again. I made four “legs” for the Shapeoko with the Shapeoko to connect it to the extrusions that are also bolted together tightly from the bottom.

After assembling the parts I ended up having a nice parallelogram that looked like this.

Some measurements confirmed that at least it is consistently proportional throughout the whole work area :slight_smile:

I squared the machine the usual way but now the front left is not touching the new front plate as it should. I haven’t had this issue with the steel front plate.

I also noticed during the assembly that the end of the factory made rails are really poorly machined :face_with_raised_eyebrow:

I will continue with some further measurements to see the effect of this gap but until than I would appreciate any suggestions!

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I had a similar parallelogram situation while assembling my stock Shapeoko, I inserted shims (= aluminum foil folder over a few times) between the rails and the plates, on opposite edges of the rail on each side, and it worked like a charm to get things perfectly square after tightening all screws.

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