MALE/FEMALE THREADED KNOBS

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Thanks for comment, Ed Weldon. Indeed, by laminating several layers of solid wood you can obtain a block of the desired dimensions. In addition, it is one of the techniques for bending wood, like this hold down clamp:

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Thank you, Camstand.
For those of us who do not have a heat press like that, one way to recycle HDPE, is to melt it in a convection oven and make blanks, from which you can make these knobs or many other of objects.

How to Recycle HDPE Plastic the Easy Way (with Pictures)

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.... There is also the option, easily available today, to make them through 3-D printing.

These are some examples of 3D printed knobs:

https://www.thingiverse.com/thing:904784
https://www.thingiverse.com/thing:1051825
https://www.thingiverse.com/thing:2451628
https://www.thingiverse.com/thing:2352177
https://www.thingiverse.com/thing:2121898