The outlined section at the lower left is at the bottom of the Sand Blaster cabinet. The sand gun is described in the rest of the picture.
Caution!
Using sand for blasting causes the particles to become airborne.
These silica particles can become lodged in your lungs and cause
silicosis of the lungs, which is not a good thing! In fact it is a
nasty thing, from what I've been reading. Make sure you have a good
ventilation system to carry away the particle laden air from inside
of the cabinet to some unpopulated location. My
system has two fans and really gets a vaccuum in the box even with
the sand gun running. So don't overlook this important part! Just use
common sense!
(There are other blasting mediums that you can use that are safer, glass beads, etc...)
The sand outlet at the bottom of the cabinet is nothing more than piece of 3/8" pipe glued into the wood bottom of the cabinet. It is stubbed into a 1/2" Tee, and adjusted via three set-screws (only two shown). The hosebarb on the right of the Tee is where the rubber hose from the suction line of the sand gun connects. The rubber hose is about 3/8 " to 1/2" inside diameter and about 3 feet long (1 meter) at the most. The third opening, on the left side of the Tee, is where the air enters when the suction from the sand gun begins. It is left open to the air. If sand leaks out of the opening when the sand gun is not being used, simply screw in a short 1/2" pipe nipple to cause the sand to pile up and stop the flow of sand.
How it works: The sand naturally falls through the pipe stub, just like sand in an hourglass. When the sand gun is not being used, the sand simply piles up within the Tee and stops the flow of sand. (I keep about 4" of sand in the bottom of the cabinet.) When the sand gun is being used, air rushes through the left opening of theTee, and brings sand up through the tube to the sand gun. The set screws are adjusted to control the amount of sand-to-air ratio. Sometimes the sand gun will "pulse" because it is picking up too much sand. The "fix" is to adjust the 3/8" pipe stub further down into the Tee to make less sand available for the amount of air flowing through. If there is too little sand coming out of the sand gun then the stub is lifted up a little to allow more sand to flow per air volume.
The sand gun is simply a venturi set-up. The air from the compressor tank is fed into the cheap air valve. That controls the on/off flow of the air. A foot controlled valve would be a lot handier, that way the gun is not so long! A piece of 1/8" automobile brake line is soldered, brazed or just jammed into the end of the valve. The other end of the brake line is hammered down to about 1/16" of an opening to form a nozzle. This brakeline is fitted through a 3/8"reducer to 1/8" compression fitting (Drilled out to allow the brakeline to go through it into the 3/8"Tee). This allows the position of the nozzle to be adjusted inside the 3/8" Tee for the best sand blasting effect. The setting is not very critical, 1/8" one way or another. Just adjust for best flow and tighten down the compression fitting.
The short 3/8" nipple is just added to the outlet of the sand gun (Open end of the Tee) to focus the sand blast. These have a very short life! The sand will eat away the thing after a few hours of operation. Be careful, the edges can get sharp! You can do A LOT of sand blasting in a couple of hours too! I have only replaced it three times since I've built it.
Disclaimer: I make no, none, not any ,never, anywhere, anytime ,any place, any dimension, whether by alien abduction or vast left wing conspiracy, any promises that this will work in your case. It works great for me though!!!!!!!!!!