Since we previously established that ball valves aren’t the best both at keeping high vacuum AND letting small gas quantities into our devices, it was clear that one more suitable (and affordable) had to be made.
Temporary plans (changed it whilist machining):
Designing process done, it’s time to machine. Everything is stainless steel 304 (except the bearings, I know).
UP: heavy turning (for my lathe), that’s 2mm chips. DOWN: some more machining.
Unfortunately, I didn’t catch all the machining process, I got very busy with it. Here’s the final product (minus the o-rings):
Fitting is not critical, but making it a good one, is best practice:
That’s some small axial bearings! (3x6x3mm). The knob is smooth because since the plunger rides on bearings, nothing should ever be stiff enough to require knurling. (also, I don’t have a knurler :P ) As you can see from the timelapse, I changed the screw design into a prong extension, easier to machine and allows for simpler play adjustment.
The ball bearings allow the actuation of the plunger without o-ring twist, both up and down. (the up might be a bit overkill, but hey, I already got the bearings, you know).
And most importantly, the gas connection:
It accepts 2mm RC compressed air tubing.
Also, do you need one? They’re for sale!