Expanding bench dog

I have a Bosch PWB600, and it's dog holes are a bit variable. I designed these bench dogs so you can twist to expand them, giving a tight fit.

Print with PETG - the flexibility is required.
WARNING: don't tighten when it's not in a hole: it may break.

There are several different upper parts with different heights

You need an M5x30 socket cap screw, and 3 M5 nuts to assemble. Put the nut into the capture in the upper part first, then screw the socket cap through it until it's tight. Place the other two nuts into the captures on either side if the inner part of the expander. Place that into the outer, and then screw the whole expander onto the upper part.

There's a knurled bit of the expander that stays above the bench, in case you can't get the explander to bite and tighten - just hold it to stop it turning. You can usually avoid using it, as long as the it's expanded enough before you insert it.