2020 extrusion tapping guide

I have just started to build a Core-XY printer (http://www.thingiverse.com/thing:1003119) and one of the jobs I need to do is tap a 6mm thread into the end of a number of the 2020 extrusion pieces. Tapping is an easy task - as long as the thread is started straight and true.

To help with this task I designed this little guide. Just slip it over the end of the extrusion and use the guide hole to keep the tap upright and on-centre.

It was designed in OpenSCAD: the source file has various parameters that can be changed according to the exact dimensions of your 2020 extrusion and the hole you wish to tap. The design can easily be changed for other sizes of extrusion, but you will have to work out the position of the hole for yourself!

Apologies for not including a picture of the finished tapping guide - I made one in black PLA, and it's impossible to take a useful picture of it! The Thingiview viewer will give a very clear idea of its shape.