Sandblasting cabinets

[Jens]

I have a 36" wide Princess Auto floor standing sandblasting cabinet. It is frustrating the hell out of me. First, the internal (optional) light died within an hour or two so I improvised with a regular 100W lightbulb stuck through one of the vent ports. Now I can see the inside as long as the outside isn't bright (think dusk). Now I am struggling with the sandblasting gun. First it was clogging with water which I fixed and now it feeds very poorly. Sometimes nothing comes out, sometimes only a few grains and sometimes a good supply of sand. It actually works ok when a good amount of sand flows but that seems to only happen once in a blue moon.
Here comes the question part ..... are any members here doing some substantial amount of sandblasting in a cabinet? If so, can you recommend the actual gun you are using ? More important, can you recommend someplace to get a proper sand metering valve ?
The PA cabinet, like so many lower end units, uses a tube stuck into the sand as the sand pickup device and apparently this is a source of trouble. I can't speak to the difference between a tube stuck into the sand and a metering valve but I would love to hear comments from anybody who actually uses a sand metering valve.
What seems to happen in my setup is that the sand fills the supply tube to the gun but the sand doesn't feed reliably into the gun itself. I am assuming (!!!!) that the metering valve only lets a small amount of sand and lots of air into the pickup tube so the blasting gun receives a proper supply and air to draw the sand into the gun.

Has anybody improvised a sand metering valve, maybe with two ball valves where one adjusts the air flow and the other adjusts the sand flow (I have no idea what all is in a proper metering valve).

As things sit now, I am tempted to just trade $700 for the 48" Grizzly sandblasting cabinet (which seems to have a metering valve) and call it done ......

[Ronmar]

How did you fix your water problem, or more exactly are you sure you have?  It dosn't take much moisture to disrupt the sand flow to a venturi/vacume type sand blaster. If you are using the same media as when you had the water problem, you were blowing moist air into the cabinet with the sand, so all your sand may be damp.  What are you using for media?  The non pressure fed guns are also sensitive to the type media.  Sandbox sand is too course, and does not flow well.  Add even the slightest moisture, and it will actually clump guite easilly.  The media you want is fine like sugar or salt.  You can buy it in bag form specifically labeled as blast media.  If you grab a handfull in your hand, it is actually difficult to hold as it tries to flow out of your hand.  Kind of like trying to hold a handfull of water.  I have used a simple sears suction type blaster for years now.  The only flow problems I have ever had were from using too course of sand, or from too much debris in the sand(rust chips, paint chips ect) or the media or air supply had too high a moisture content.  The little sears hopper(about 5 gallon) has a fine mesh strainer in the filler hole so you can filter out the debris when you recycle the blast media.

[vdubnut62]

My Harbor Freight pressure fed blaster uses a ball valve arrangement to meter the sand, I could post pics if you wish.
Ronmar is right on target, ANY moisture will gum up the works and ditto on the trash in the sand.
Ron

[vdubnut62]

Over the years I have used several different (and also VERY cheap) vacuum pickup type blasters, and they were all a PITA without exception.  But the Sears one Dad had when I was a boy was the least problem of the lot. I just assumed that it was a quality issue.
Maybe Sears is on to something? The worst one had a pickup made with a tube inside another tube, I guess it was theoretically supposed to pick up sand , but it rarely did.
Ron

[mike90045]

Somewhere, it should say what grade/screen size of sand the system is designed for. I don't think you can just throw any sand in.

[TimSR2]

Take it back to Princess Auto and tell them it is a piece of junk and get your money back.

In Langley (my hometown) there is a business that rents sandblasting time... they have glass beads , walnut shells, everything! You could rent their machines for many hours for the cost of what you have now. No maintenance and no shop space required. Some stuff is just better rented than owned. IMHO a sandblaster is one of them.

[NoSpark]

I've been thinking about building my own blasting cabinet for a year now, it really makes a mess of the yard and me( and the shower). I have a Sears Craftsman 50lb suction type blaster that works great. I would just use this in the cabinet. The only problem is when using Black Beauty a cavity forms at the bottom of the sand tank at the hose inlet. I just give the tank a little kick and away she goes again. Also if a plug forms in the hose or at the nozzle or hose inlet I just put a finger over the nozzle and blow back through the line.

[Ronmar]

Also if a plug forms in the hose or at the nozzle or hose inlet I just put a finger over the nozzle and blow back through the line.

That is an excellent hint.  I forgot all about that one.  Putting your finger over the nozzle and pulling the trigger works very well to clear out a clog in a suction fed gun. 

That sounds about like the same hopper I have.  It has a flat bottom and the sand feed is on one side.  As it gets low, it finds it's angle of repose and the media cant flow to the port.  A kick every now and then keeps it flowing.  A funnel bottom blast cabinet should feed well with the pickup right down near the bottom...

[Ronmar]

The 50# hopper we were refering to is basically a tall narrow 5 gallon bucket with a hose barb fitting down on the bottom edge.  No dump mechanism, so all a kick or a shake does is settle the sand toward that hose fitting.  Inadvertently dumping the sand from a cabinet hopper might be funny once, as long as it was happening to someone else:)

[elnav]

I have one of the Princess Auto sand blasting cabinets Jens is talking about. Got it cheap from a welder who discovered it  was too small for the work he was doing. I plan to use it outdoors and am wondering what grit  to use. A local place in Quesnel sells 'enviro grit'  (basically crushed glass)  and it is  incidentally sold by Princess Auto in addition to the regular sand grits .  I saw a mention about not using silica.  Pardon my ignorance but what's bad about silica and is crushed glass  in the same catagory?
 

[quinnf]

Quartz sand, silica sand, crushed glass, they're all silicon dioxide or silica.  Some forms of silica are crystalline, some amorphous, but all are dangerous to your lungs.  Unlike environmental dust, the above materials break into fine particles with sharp edges that lodge in the alveolar sacs where oxygen and carbon dioxide are exchanged from the blood.  They aren't easily removed by mucous, to be coughed out.  Every time your lungs inflate and deflate, the sharp edges work against the delicate tissues, causing scar tissue to build up.  The damage is not reversible. 

Whatever you use for blasting grit, even steel shot or crushed walnut shell, always wear a respirator.  Not a cheap dust mask, a real respirator with replaceable cartridges.  You'll protect your lungs and you'll be more comfortable. 

Quinn

[elnav]

Okay I get  the idea. However since we are talking about  an enclosed cabinet  How much does this apply?  Yes I do have  industrial respirators, those with replaceable filter packs  but if the  cabinet is enclosed  and  none of the air gets outside is this a major concern.
My buddy has one of those face masks that actually blow filtered air into the helmet and across the face mask  to prevent fogging.  Maybe I need to use one of those as well.  I can't imagine anyone in their right mind breathing  dust of any description.  Thanks

[rcavictim]

I have one of the Princess Auto sand blasting cabinets Jens is talking about. Got it cheap from a welder who discovered it  was too small for the work he was doing. I plan to use it outdoors and am wondering what grit  to use. A local place in Quesnel sells 'enviro grit'  (basically crushed glass)  and it is  incidentally sold by Princess Auto in addition to the regular sand grits .  I saw a mention about not using silica.  Pardon my ignorance but what's bad about silica and is crushed glass  in the same catagory?
 

I recently got some of that crushed recycled glass at Princess because it went on sale cheap and I had never tried it before. I don't mind a bit if it gets mixed with the gravel in my work yard.  I find it nowhere near as aggressive derusting steel than the silica blasting sand.  It depends on what you want it to do.  The silica has razor sharp surface contours that can cause damage if inhaled in the lungs.  The condition this leads to is called silicosis.  It can cause early death.  The crushed glass does not have the same health danger as far as I know but it is still a good idea to always wear a respirator, hearing protectors and a full face shield when sandblasting with any media.

edit: Quinn,  Thanx for that excellent explanation of the injury mechanism.  I stand educated and corrected on my uncertainty about crushed glass being harmful to the lungs.

[quinnf]

Since you're blowing large volumes of compressed air to suspend the blasting sand, that air has to go somewhere.  Some cabinets have an exhaust filter, some just have a screened port on the back that a ShopVac can be plugged into.  And the cabinet isn't airtight, so dust can escape.  Unless you're doing an awful lot of blasting, it's probably no huhu.  But with all the stuff we breathe these days, and the surprising numbers of people I know of, most of whom have never smoked, who contract lung cancer, it's enough to make you a little paranoid. 

Then again, it's not just the grit.  The stuff you're removing can be bad for you, too.

FWIW, I have a powered air-purifying respirator (3M Air-Mate) http://www.envirosafetyproducts.com/air-mate-12-system-assembly.htmlthat I use for woodworking, sanding, grinding welding slag, etc.  At the end of a particular task I no longer cough, wheeze, and blow stuff out my nose. 

Quinn



Quinn

[elnav]

FWIW, I have a powered air-purifying respirator (3M Air-Mate) http://www.envirosafetyproducts.com/air-mate-12-system-assembly.html that I use for woodworking, sanding, grinding welding slag, etc.  At the end of a particular task I no longer cough, wheeze, and blow stuff out my nose. 

That is the model my buddy has. I acquired by chance one of the PaP machines used by Sleep apnea sufferers  which pumps filtered ( HEPA filter)  air  to a face mask.  I was thinking it would be a suitable substitute if I added either the helmet or just the normal face shield I normally  use  grinding or rust removing. 
Right now $500+ simply isn't in the budget.