Analog (mechanical) pressure gauge for a single cylinder filter

How can I put a pressure gauge on a metal cylinder while maintaining vacuum, using only a lathe and/or a bench drill?
These guys made a manual espresso machine and specify using 30 lb of pressure in the manual. In order to determine the correct pressure, they literally tell the user to push down on a kitchen scale. I'm considering a competing product, and that seemed like a rather obvious oversight. Surely there's an economical analog pressure gauge on the market that can be attached to the assembly? For instance, a cheap blood pressure monitor costs ~$35. Surely it's sufficiently accurate?

Now, the system I have in mind uses a cylinder that may or may not have pre-attached valves. Assuming even the predrilled valve is the right size, how do I attach such a gauge without compromising working pressure and volume? If there is no valve (a solid cylinder) do I have any way to attach one using only a lathe and/or drill press (ie no welding)?

Many thanks in advance



Science Advisor
Welcome to PF.

Gauges are usually threaded. Adaptors are available for any thread. You could drill the metal, then cut a thread into the hole, or connect the gauge to an existing port.

Rather than measuring the strain in the handle for display, you could make a flexible handle with a pointer, like an indicating torque wrench.

It takes about 14.5 pounds to pull a vacuum in a one square inch cylinder, (atmospheric pressure). If you came up with a two square inch sealed cylinder you could push it down once to create the vacuum, then relax while the fixed 29 lbs pressed the coffee through the filter.

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