The Origami Forum

Hello,

Let's say, you have a paper roll, and you're not absolutely sure that the cut at the end of the roll is perfectly perpendicular to the 2 other edges.

Is it possible to ensure it by folding alone ?
If not, what is the most precise way the measure the error ?

Thanks in advance.

Anything with a perfect 90 degree angle. A carpenter's square. But even a picture frame or something with a corner (90 degree angle) just line up the long side of the paper with one of the picture frame's edges and cut along the edge to the right of that top edge. if this doesnt make sense, i'll post pics

It does, but I'm not sure this is a very precise solution, especially when you don't have a square long enough to trace through the whole width of the roll... (let's say I have a 1m wide roll)
You have to first use a square to trace partially through the paper's width, then take a ruler and trace along the line you started.
From my experience, whith this method, the wider the roll, the bigger the imprecision at the end of the traced line.

If the paper you are cutting from isn't a "perfect" rectangle (as in, straight edges, 90 degree corners) there is no way to get a perfect square from it by folding alone.
How I make squares from deckle edged paper, or from a rhomboid, is I use a carpenter square to trace over one corner. Then, depending on the length of paper, you can get a meter/yard stick and lay it above the line you drew from the carpenter square. This can extend the perfect right angle a bit, and helps you lay down your carpenter square in the right area. After you get three corners, use your meter/yard stick again to cut straight lines down all the edges. Once you have a rectangular shape, longer in height than width, fold the top corner down to the edge and line it up. Cut along the top edge of the paper, which now should be laying towards the bottom, and you have a perfect square

Well it's more like this :

But it gave me I idea... maybe if I did this:

to get 2 90° angles, and then I could use the standard method to make a square out of a rectangle...
That could make it.

Ok, I didn't understand what you meant.
In theory, yes, that would work. Only if you know the two edges are parallel to each other, though. Otherwise, you'll get a rhombus type shape, and be unable to do anything with it.

No, it should work because it is one straight edge and you are making a 90 degree angle by folding it onto itself. I'm pretty sure that the two sides are parallel to each other. Those rolls are usually machine cut and therefore very accurate regarding their width.
You see Phillip even if they are like that // you'll get a right angle that will further on allow you to get a nice square if you fold one of the sides onto itself.

Using large paper, there is still quite a large thing we like to call human-error. You will not get a perfect square, and you will live without ever making a perfect square. Everyone does.

Anna, I had meant more like: / |
but the slanted edge slightly less profound. I just don't know what that shape is named.

Phillip, thats still a trapezoid

yea i haven't slept in like 2 weeks due to being sick, so my brain isn't working on full caliber

I think one should conserve paper and make origami at home with used paper. One should use fresh origami paper for only professional purposes. GO GREEN

The long edges of a roll are always perfectly parallel, as long as the circles on the sides are (they always are). It has nothing to do with presicion of the machines. I use the method from the second drawing every time my mom steals paper off my roll and makes a jagged cut. it works great.

Well Malifold consider yourself lucky. The roll i have gives me so much trouble.Every square i cut ends up a trapezium. I am forced to use an L- Square.

I went to a plastics shop and invested about $10 for square templates. Haven't had a piece of paper out of true since.