Al, 100lbs of pressure is what I use in my blaster. The one I use is much like the Harbor Freight jobs, both styles, the cabinet and the "outside" model. I had a Harbor Freight cabinet job, but gave it away eventually.. The "glass" window was actually plexi-glass, and with the sand particles flying all over inside of the cabinet, it scratched the bee-jeepers out of the window so bad, it was next to use-less..Also the rubber gloves wore out.. I've used "Black Diamond" blasting media as well as regular old play sand. I like the play sand as it's CHEAP, like me..The blasting material must be completely dry or it will clog up your lines. Also, I use a strainer to sift out larger particles of media that would other-wise clog up the lines. Be careful with the glass beads, as I've heard the glass bead dust is bad for your lungs. If I'm going to do alot of blasting such as wheels or parts from cars, I use a respirator.
Flyernut I have never seen a Harbor Freight blasting cabinet so I don't know about their construction. My Snap-On cabinet has a real glass window, not plexiglass, an exhaust fan, and catch bag so no breathing dust. I had several extra glasses cut from the original which are easily changed out when, just like plexiglass, they get cloudy from use. Just not as often. Two 60 watt lights in side the cabinet provide lighting. Never had one break in all my 20+ years, more like 30 as I think about it. Glass beads do not clog if you have a humid day. If you get a diminished amount of blasting media coming out because of blasted off paint chips or rust chips, simply put a gloved finger or similar solid object tightly over the nozzle and pull the trigger for a couple of short bursts which back flushes and clears the line. Yes a plain old house hold strainer also helps to run through the glass beads to collect foreign material once in a.
The original rubber gloves did wear out in about 2 years of constant daily use when I was into the car restoration business. Snap-On has replacements but I found a better pair at NAPA, cheaper and made heavier. Haven't changed them in I don't know how many years. Granted now days I don't do as much blasting as in the past but still at least once a week.
Maybe all the added features I mentioned, the exhaust fan, catch bag, and glass instead of plexiglass is part of the reason my Snap-On cost more compared to Harbor Freight.
Not to mention probably paying extra for the name. I know that Snap-On does have other models since I bought mine lo those many years ago.
I have used the Black Diamond as well in my cabinet with good results on cylinder heads, exhaust and intake manifolds.
All in all with all the thousands of dollars I have invested in tools, that cabinet is one of my better investments.
Now out door actual sandblasting does indeed require a respirator not to mention a head covering hood, coat and gloves. I spent may hours doing that to car bodies and even a couple of farm tractors.
So there you go mopac Al. More information on your choice.
Kenny