M8 Knob for MFT with threaded insert and washer

Designed this knob to use on an MFT style tabletop, to hold things down.

I have tried iterations of this design using a simple threaded nut, but found that the knob would always break, even with solid wall thicknesses of 3 mm. In this version the contact area between the threaded insert and the knob is greater so it is more likely that the knob will slip in your hand than to break from the torque applied.

The washer is 30 x 8.4 x 2 mm and is a large standard for M8 screws, like this one:

https://www.bauhaus.info/unterlegscheiben-dichtungsringe/profi-depot-karosseriescheibe-vz/p/10826772

The threaded insert I used is 20 mm long and can be screwed using a hex key, like this one:

https://www.heimwerkertools.com/werkzeug/befestigungsmaterial/gewindemuffen/2994/haefele-eindrehmuffe-fast-aus-stahl-mit-abdeckrand-und-innensechskant?number=1003838&gclid=Cj0KCQjw06-oBhC6ARIsAGuzdw3zv-30x9l6FFAqQYOJsaat24nls3UpKbZWuDWYGty9LUqq7fo8MgwaAh1_EALw_wcB

You will need to turn on supports for this print.