Now for the fun part. In this step, you'll be drilling a hole in your nice shiny new pressure cooker. I know, it's tough, but it's for a good cause.
You're going to need:
- A metalworking drill press
- The pressure cooker
- A 3/4" drill bit
- Several smaller drill bits
- Various clamps and bits of wood
- A deburring tool
Because all of my other fittings are 1/4" NPT, I chose to use a 1/4" NPT bulkhead fitting for the vacuum port into the pressure cooker. Of course, the fitting itself is much larger than 1/4", so we'll need to drill a bigger hole, namely a 3/4" hole. To do this you'll need a drill press big enough to handle your pressure cooker. You might be able to use a hand drill, but with a 3/4" bit, I wouldn't recommend it.
Start by removing the lid from your pressure cooker (mine came with the lid attached), and notice that there's a rubber gasket inside the lid. Don't damage the gasket; we'll be using it later. We won't be using the lid, but it's protecting the gasket, so for now just set them aside so we can come back to them later.
Next, set up your drill press in whatever manner is appropriate for your equipment, shop rules, etc. If you're at a shared workspace, make sure you don't use the drill press that's set aside for woodworking. You'll get in trouble, and you'll probably ruin it.
We're going to be making several cuts because you can't just go straight for a 3/4" inch hole. Not easily anyway. Pick out several smaller bits that you can use to work up to the final size. I started with a 1/4" bit, and a few others that I found in a drawer of old bits. But don't use overly dull bits, or you'll have a bad day.
With that in mind, lower the table until the pressure cooker fits beneath your first drill bit, and then find some wood and clamps to clamp everything to the table. Get everything lined up so that your final hole will be an inch or two above the bottom of the pressure cooker. If yours has a rounded bottom, like mine, then move the hole an inch or two above the top of the rounded part. Once you get everything lined up, tighten the clamps and lock the table in place.
At this point you should have everything lined up, clamped down, and locked in place. Load up your smallest drill bit and set the drill press to a speed that's appropriate for whatever bit size you're starting with. Now, drill your first hole. If you're using a huge pressure cooker, it will probably vibrate and chatter a lot. Just go slow, and back off if things get too crazy.
Once your first hole is finished, admire your handiwork for a minute, then move up to a larger bit. Keep going until you have a 3/4" hole. Don't forget to lower the drill speed as the bits get bigger.
When you're finished, find a deburring tool and clean up the edges. That last bit probably made a mess.
Congrats! That was the hardest part. It's all Easy St. after this.