For those that read my long diatribe about making collection plates, there was a sidebar comment about my making a vacuum pump. Here it is. It is about 98% complete. I'm missing a cable protector for the power cord that is rubbing against the knock out hole on the switch box. I also have a leak most likely in the headstock vacuum adapter. I applied several coats of sanding sealer to the outside but probably should have done the inside, too. Not a big problem. I still get 20-21in/hg through the entire system which is enough to collapse a thin bowl. The pump draws 25-26in/hg until it hits the headstock vacuum adapter.
At last month's woodturning club meeting, some guys did a demonstration on vacuum pumps. They bought several kits comprised of the pump, inline filter, muffler, some pipe fittings, gauge and double-sealed bearings. For a $100 I bought a kit and with another $37 you see the end result. My $37 included the valves, some additional pipe fittings, tubing, power cord and threaded brass lamp rod.
Here is the recylced piston pump setup mounted to a board and wired to a simple switchbox with a 9' extension cord. Wish I had gotten a longer one. The muffler is the small brass piece protruding from the back top left corner of the pump. Much needed.
Here is the inline filter and large gauge. From a distance, my 50 yr old eyes can see the pressure just fine. The valve at the junction allows me to vary the pressure going into the headstock by diverting air down. I am missing another muffler on the downspout but the noise isn't that bad when being used.
This pic is showing the headstock vacuum adapter I turned for my Powermatic 3520B. This adapter mounts in the hole on the handwheel with a friction fit. The core of the adapter is 2 double-sealed bearings (epoxied) and a pipe-fitting also epoxied. The brass lamp rod which runs through the headstock and out the spindle is also epoxied into the adapter. The bearings allow the headstock to spin freely. The valve at this end allows me to turn the pressure off and remove or re-situate a piece...without having to walk over to turn the vacuum pump off/on.
This pic shows the spindle-side adapter. Instead of turning one to fit the #2 morse taper, I re-used the one from my Holdfast setup; however, I did add the nut on the end to securely clamp the setup to the headstock spindle.
This pic shows the 3 different sizes of vacuum chuck I made. I used PVC couplings not pipe. Couplings are thicker. Each chuck is mounted onto the spindle with a tapped & threaded block of maple (and walnut). I had a supply of maple that I had threaded a year or so ago. I used them for jam chucks for various pieces. Two of them weren't really long enough and hit the brass rod/nut. So I laminated some walnut to the maple chuck and cut out the recess. I still get maximum holding on the threads. Then it was simple to size the chuck to fit the inside diameter of the couplings. Generous epoxy and clamping, profiled the PVC edge then I CA glued some orange Funky Foam to the rim. Funky Foam will hold a vacuum and still protect the piece.
I'm hoping you can see the threads in this pic.
There are tons of folks who have posted how-to's online. I have zero electrical/mechanical background.