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Tuesday, June 08, 2010

Ruler Off Target

I bought a wooden 12" ruler from Target.


I like rulers for drawing straight edges on paper.

Does this ruler look like you can use it to draw straight edges?



This pen has some straight edges. Does this ruler look like it draws straight edges?



I made some ad-hoc graph paper against which I could mark the path of the ruler's edges. (I couldn't use standard rectangular graph paper on an 8.5x11" sheet since the ruler was 12", so I made one this using GIMP.)


My measurements were made by placing the corners of the ruler edges along the center long line and drawing the path. The short lines help identify the degree of error.

A good ruler would not deviate from the center long line.


Let's see what path the inches edge makes.


Can you see? Perhaps a close-up would help:


Here's the path of the centimeter edge.



Here's a closer look:


Looks like the centimeter side goes about an eighth of an inch off target. Well, I can't be certain - I measured that with my arc-y ruler.

Where did it come from?


Too bad. I don't blame the Chinese manufacturer for this crappy construction. I blame Target for accepting it.

And to be clear, the reason I dislike this so much is that people buy their school supplies from Target. How many students have rulers that just suck? A student can't understand geometry when their tool is this bad. Will a poor student have the money to replace it?

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