The easiest way to transform a straight rack that it meshes with a helical gear, is to use a skew operation. Try the following code with rack() from your lib: > a = 30; // angle to skew > // ... > multmatrix([[ 1, 0, a/45, 0 ]]) // skew transformation > rack(mm_per_tooth,n5,thickness,height); -- View this message in context: http://forum.openscad.org/Changing-straight-gears-to-helical-tp21126p21127.html Sent from the OpenSCAD mailing list archive at Nabble.com.