I have modified my previous version (2) of the adapter. This one has a little tighter tolerances. It uses a 1/4-20 three-prong t-nut to mount the adapter, allowing the threads to be closer to the bottom of the base, for those tripods with a short mounting screw. The t-nut also provides for more threads of the 6-32 screw into the plastic of the base. The base has recesses for those plates that have stop-screws. The knob size is better. I have included a camera quick release plate with this design. I found that some of the plate designs didn't fit my standard Arca Swiss type adapters, so I decided to add one here.
As with the first version, I wanted the adapter to fit my existing plates and I wanted a single knob to tighten or release the clamping mechanism. I considered using springs to spread the jaws, but wanted to reduce the parts, so I flared the end of the knob to fit a dovetail-like slot in the sliding part of the jaw. The knob has a hex recess into which is pressed a 6-32 nut. I pressed the nut into position with a vise and a nylon bushing. After sliding the knob into position in the slider and placing the slider into the base, a 6-32 x 2" machine screw is screwed through the knob and into the base until it just pushes into the recess for the 1/4-20 t-nut and is then backed out a few turns. Then the t-nut is pressed into the recess. I just used a 1/4-20 machine screw to pull the nut into position. Then the jaws can be opened and closed by turning the knob, clamping on to a standard Arca Swiss plate or the plate included in this design. The commercial plates I have purchased that are Arca Swiss compatible fit this adapter.