Making a Self Tapping Fitting

File a notch across the threads of a brass hose fitting, as shown in the photo, and it will cut its own threads in the vacuum port. It will even cut threads into a wooden base.

Brass is soft, and the notch is easy to make. But once the fitting is installed, leave it in place. The notch will cut each time you turn it into the hole. Removing and reinstalling the fitting too many times will result in a loose fit (and a vacuum leak).

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Vacuum tape

Quick-disconnect rminci x-—Vacuum tape

The final step is to plumb the jig. so the vacuum valve can evacuate the air from the vacuum chamber. First, you have to drill a vacuum port, a hole that extends from the exterior of the jig into that vacuum chamber. The placement of the hole isn't critical; it just has to reach inside the chamber. Three alternatives spring to mind, and thev are shown in the drawing Vacuum Port Alternatives.

After boring the port that's appropriate for the jig, you install a fitting, usually a barbed hose connector. The plastic "quick-disconnect" fittings that typically come with the vacuum kits must be sealed into the port with a silicone

TYPICAL VACUUM-SYSTEM FITTINGS Quick-disconnect fittings Plastic T-connector male female

Press latch to release female connector from male.

Plastic pinch clamp

Multi-position

Plastic 4-way connector latch

Squeeze to close off vacuum in hose.

latch

Squeeze to close off vacuum in hose.

Pull tip ^ to release hose.

Hose

Pull tip ^ to release hose.

Hose

Brass barbed hose connector

Brass coupling, male/male

Brass nipple, male/male

Brass coupling, male/male

Brass tee, female

Brass 90 elbow, female

Brass 90 elbow, male/female

Brass stop cock (closed)

Brass stop cock (closed)

Brass stop cock (open)

caulk. I've also used threaded brass and nylon fittings. Use a tap of the appropriate thread to cut threads in the port, then install the fitting.

To carry the air from the jig to the vacuum valve (yoa remove the air from tlic chamber to create the vacuum, remember), use any rubber, vinyl, or plastic hose that's stout enough to withstand a vacuum without collapsing. The hose supplied with the system I use is ^6-inch-insido diameter, /i6-inch-outside-diamcter clear vinyl hose. It works perfectly with the quick-disconnect fittings, as well as with the brass and nylon fittings. And the local hardware store has yards of the same hose for half what the vac-pump maker charges.

If you choose to use the quick-disconnect fittings, you plug a male fitting into the jig and a female into the hose. Then you just disconnect the hose from one jig and reconnect it to another. What I've found is that the hose slides onto barbed fittings easily, and it can be removed from thera just as easily. So you can use the same length of hose with different jigs whether you use the quick-disconnect or the regular fittings.

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