How to Build Things Square. (It Can Be Easier Than You Think.)

Building something correctly can be weirdly subjective. It all depends on what your building and what you are building it for. Assuming you need something an exact shape it can be amazingly challenging. You quickly realize most materials are nominal dims and can vary allot. On top of this most work surfaces are not actually square.

The steps will be each type of measuring square.

For checking the square of most things you will need a minimal list of tools. Any other tools that can make things easier I'll discuss in the each step but aren't required.

• tape measure
• string
• clamps
• some sort of work surface

Yep that is it for a bare minimum setup.

Measure across the square item in a few points.

This is how most people measure to see if something is square. They continue building and then notice hey, this isn't actually square. Measuring like this measures to check if something is parallel. Not actually 90 degrees.

I'm using CAD to show my example. In the first square you measure across in several locations and get 1'-0" all around. Square, or is it actually like the left example actually out of square by 1".

You need to add the second step to see if something is truly square. The measuring the diagonals, if the item you are building is truly square the diagonals will be the same. The right example you can see where they both are 1'-5" but the left one that isn't square is 1'-5 11/16" and 1' 4 1/2".

This tells you something is off and it requires adjustment.

This is where the string and clamps come in. You can have accurate measurements across your square and accurate dims along the diagonals but you object could still be shaped like a potato chip aka twisted. Now to check this you can clamp a string along the diagonals. These strings should naturally want to take up the same space. If you move either string away from other the other string shouldn't move. (I guess technically it would want to move about half the thickness of the string.) If the either string moves or they never even touch the item is not square.

Photo 1: Use a square, or square clamp. This will work provided your material is true otherwise the corner might be square but if your part has a twist to it your out of luck. Also if you clamp a square to something with not a clean side it will still be crooked.

Photo 2: Shift your part. This can be done a bunch of different ways. The easiest way is if you can take your measurements before you assembly you can just move the the parts. Commonly though after you start building you need to keep taking measurements because things shift. I have found an effective method is to use a ratchet strap and compress the larger of the two diagonals this will cause the other diagonal to increase in size making the part square.

Photo 3: (yes I am re-using the photo) Shim your supports. If you know you have a twist to your part before its assembled its easy enough to shim. I have some shim stock but you can use washers or coins to get you close. If its already assembled often its just brute strength to twist it back.

The best way to do this is get a fairly nice welding table that is milled and have a true flat spot to do your work. I have only recently got this and it does help it doesn't remove all the issues you still need to check to make square just makes life a bit a lot easier. Most of my building of smaller projects was on my original welding table which consist mostly of a 3/8" thick chunk of steel that anything but straight.

If your work surface isn't straight minimize how much you contact it. It is easier to level out 3-4 locations opposed to leveling out essentially an infinite amount of points. When you lay a part down on a table you get essentially 100% contact area. You can check the corners and say yep is square but be off in the center due to a rise or dip in your work surface. This exact thing happened to me when I built my trailer. I built the base on the floor and there were dips and rises in the concrete thought it was flat until I took measurements and it was awful. I had to take it apart and put it on jack stands. Once it was on jack stands I did not have the floor inputting its out of square into the part.

So what tool mitigates the problem? The answer is your tape measure, check square often and this helps you fix your issue when its not hard to fix. I can move 4 pieces of steel or wood very easy when I have it laying on the table. It takes a bit of effort if the part when its tacked or screwed together. But once that part is fully welded or glued together and I find out its out of square its time to cut apart or toss.

Its that simple right just design it to be square so it is square.

Well no.

Oh well design it with such loose tolerances it doesn't matter.

Yes but also no.

Just because you say its square its obviously not. Take a look at nearly any wood at home depot and you can see that. Likewise if you make everything with insanely loose tolerances you items will have a sloppy build that has no precision.

Option 1: For tables and such add adjustable legs. A 5 dollar screw in adjustable foot allows adjustment between your build and the floor.

Option 2: This is more for welded assemblies, cut your part short. Leave about 1/16" gap between your two parts then tack weld it it. This allows the tack weld to act as pivot in multiple directions. If the part is in contact you can only pivot in one direction. Once the assembly is tacked together tack in another location and check and repeat. Once the assembly is locked in you can weld out.

For bolted or screwed assemblies this the equivalent to a tack weld would be do not fully tighten down your part. Glued assemblies commonly have a few seconds to minutes of open time where you can make adjustments.