I found this interesting instructable about making a postal scale from old CDs. The completed scale seems accurate enough for most peoples needs. Check out the link for more information about the build, including how to accurately calibrate the final scale using quarters.
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More contributors: Mark Frauenfelder (Editor-in-Chief, MAKE magazine), Kipp Bradford (Technical Consultant/Writer), Chris Connors (Education), Diana Eng (Guest Author), Peter Horvath (Intern), Brian Jepson (O'Reilly Media), Robert Bruce Thompson (Science Room)
Behind the Scenes at MAKE and CRAFT
In January, many of the remote MAKE/CRAFT team members (myself included) convened at the Maker Media headquarters at O'Reilly Media in Sebastopol, California. Take a look behind the scenes of your favorite DIY publications as Goli Mohammadi gives us...
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