As announced before, the next video of the machining is available. There, you see some drilling, chamfering and cutting of threads.
Drilling these small holes really f***ed me up. At the beginning I used cheap 0.214mm drills, until all of them had been broken. Thereafter, I bought not so cheap 0.2mm drills, which also broke. Finally, the 0.3mm drills worked. I could drill them all with the 4 drills, I had available. Now they are also broken. Thus, when drilling these small holes, it really depends on the speeds and feeds for the drills you use. For the latter ones, a guy I know from facebook sent me the drills for free. Furthermore, he supplied me with correct speeds and feeds. Or at least, the speeds and feeds he had been successful drilling holes. So, at this point, thank you very much for the drills and your knowledge!
After drilling the small holes, the remaining stuff was quite simple. Cutting the M6 threads into the holes that can be used for further clamping of work pieces had been done with a whirling thread cutter. Chamfering the outer boundary, and all the holes, a 8mm 45° chamfer mill had been used.. The vacuum holes had been chamfered just a little bit since the diameter should be about 5mm.
A few days ago I tested the 5mm holes with some dowel pins. They can be used to align work pieces. I was really surprised how precise the 5mm holes had been drilled. The dowel pins just have a very slight amount of play, so that it isn't too hard to remove them after aligning.
At the end of this project log I want to announce some good news. The bottom plate had been milled successfully. A video showing the machining process will be published in a few days or maybe at the end of next week.