Libre parameteric chisel

This is a customizable symmetric chisel meant to be printed on a metal RepRap printer like this [one](http://www.appropedia.org/Open-source_metal_3-D_printer).

Open in customizer to change the geometry -- see orignal OpenSCAD code for starting sizes.

This is part of a project being carried out by members of the [Michigan Tech in Open Sustainability Technology Research Group](http://www.appropedia.org/Category:MOST). to make [open source appropriate technologies for sustainable development](https://www.academia.edu/1507915/3-D_Printing_of_Open_Source_Appropriate_Technologies_for_Self-Directed_Sustainable_Development).