This is a complete re-design of the three suspension ring mounting parts for a cheap Hobart welding helmet. I wanted to repair an old helmet that had lost the screw-pin piece and stripped the knobs. I tried NuRxG's parts ( https://www.thingiverse.com/thing:2839844 ), but the main part I needed was the screw-pin and his printed one didn't come out very well (and I don't expect would last very long, due to being a thin part printed on the Z-axis), so I decided to spend a bunch of time making my own parametric version.

A minimum of one 1-1/4" (or 30-35mm) long screw and either a matching nut or another short screw (~1/4" or 6mm long) are required for assembly of each side. The main screw should be a US #6-#10 or M3-M5 (#6 is what I'm using and what customizer defaults are set for). The set screw (if used) should be a #6 or M3.

There are three ways you can use these, depending on the hardware supplied:

1. Screw and nut. Friction with the plastic keeps the screw in place, but a nut is required to reduce friction on the knob. (Beware, the screw may start spinning over time.)
2. Screw and set-screw. File or grind a small flat next to the head of the screw (see picture) and hold in place with a set-screw. The knob does not need a nut, but will need to be tapped before use (using the screw or an actual tap and drill), and would probably benefit from a drop of grease. (Use this method if you want the knob to be extra-snug.)
3. Screw, set-screw, and nut (recommended). This combination will probably hold up the best over time.

If you get the hole sizes too small you can easily drill them out, just make sure to leave enough plastic for the screws to retain a firm grip where required.