At first I thought it wouldn't fit, too - but after removing some artifacts from the (although fine and well calibrated) printed parts - effectively making chamfers on all edges where the extrusion has to enter, and also on the extrusion itself - it *did* fit, however very tight. The extrusions had to be pushed in with quite some force (which I believe is a good thing for precise angles).
>> which PLA did you use? <<
Nuclear Green from reprapworld.com
>> I am fighting since one week <<
If chamfering doesn't help: maybe your printer calibration is off, at least for hole sizes.
>> which PLA did you use? <<
Nuclear Green from reprapworld.com
>> I am fighting since one week <<
If chamfering doesn't help: maybe your printer calibration is off, at least for hole sizes.