This is not a "how to make" post but a "how not to build stuff" warning.
The following pix. are pretty self explanatory. The Tee slot grooves on a rotary table were machined too thin at the top. In this case it only took very light force to break.
I fixed the table by machining it flat and drilling and tapping to bolt on a 12mm thick piece of steel plate, which I then machined flat and cut grooves for the Tee nuts.
The moral of the story is to always look for the probable failure areas of any new tools. Especially those from the east.