Compression Fitting Assembled with BA Gauge
The BA gauge which I want to use to measure the ultimate vacuum level is a glass tube type and lacks a flange. The solution is either to torch a metal fitting out of kovar (expensive) or to use a simple viton O-ring compression fitting. Since the latter isn’t destructive and I don’t yet trust my glassblowing skills, I went with the compression fitting.
Instead of buying a compression fitting from a vacuum supplier, I decided to go ahead and turn one on the lathe for practice. The combination of threading, tight tolerances, dissimilar materials and knurling made this the most advanced lathe project I have yet taken on.
An exploded view of the pieces is shown below
In order to prevent any burrs in the threads of the steel nut, a thread form was turned and is shown below. Made from the same steel, the threads were worked against the nut threads under force for multiple mate demate cycles until the motion was smooth.
And finally a photo of the gauge connected to the chamber. Just one step closer :)
Edit: If I made this piece again I would have added a small internal shoulder for the neck of the gauge to sit on so that it couldn’t be pushed all the way into the flange and potentially hit things inside the chamber.