Welcome to the BugShop FAQ

Intro

First of all, some of the governing rules in my garage.  The larger something is, the more useful, and often used it must be.  When I first started the resto on my '57, I built a sandblasting cabinet out of plywood.  It had the rubber gloves, the window, the light inside and eventually it had the shop vac/dust collection system.  But I actually used the thing to blast something maybe 3 times in 3 + years.  It took up WAY too much space and once I decided to farm out all my larger scale sandblasting jobs (Beetle body included), I dismantled it.  In the years since, I found that I could buy good silicon carbide abrasive for dirt cheap in a neighboring town, and have found many more instances to use my "blast out of a bucket" gun, mostly smaller part restos.  I would typically just go out to the middle of the driveway with the airline, bucket and gun, and blast away.  Then sweep the abrasive up, usually throwing it out in the woods, and then spending the rest of the day picking the black grit out of my ears.

Recently a fellow enthusiast who I was regularly trading e-mails with (he is restoring a '50 sunroof) suggested making a blasting cabinet out of an old Rubbermaid storage tub.  It hit a nerve with me because a) I had been doing a bit more blasting in recent weeks, b) had a part project that needed blasting in the coming week, but the driveway was coverd with snow, and c) had bought two big Rubbermaid bins with covers at Home Depot a year or two ago just because they were cheap and only found a real use for one of them.  On a Saturday morning with virtually nothing on the family calendar, I decided to give it a shot.

But before we get to the pics and details, let me cover a few things about sandblasting in general.
 

Air Requirements

Sandblasting is one of two things in autobody work that requires large amounts of air (high volume, low pressure, or HVLP, paint spraying is the other), and large amounts of air mean large compressors.  See my "DIY Paint Job" article for more info on compressors and their capacities.  Also see Page 9 of the '57 resto series for details on just what a "high volume" compressor setup is.  What this probably all means is that unless you already have a very large compressor (notably a 2 stage 220 volt or greater unit), you won't be doing any large scale sandblasting.  But if you have, or are going to buy, a single stage, 120 volt unit, you can do some sandblasting.  So just how much of a sandblaster will your compressor operate?  Well as I detailed in the Paint article, compressor output is rated at cubic feet per minute (CFM) at a given pressure.  And since you will be sandblasting with the maximum pressure (or near to it) that you compressor can put out, you should concern yourself with the 90psi CFM rating of your compressor when sizing up its capacity for sandblasting.  My 3.5hp Sears compressor rates at 6.8 CFM at 90 psi.  And most single stage, 120 volt units are going to top out at 5-6hp and around 7 CFM at 90psi.  Smaller compressors, like 1.5 hp will probably do the 3-5 CFM range.  Keep in mind also that sandblasting is a continuous air flow operation.  Unlike some air tools, like impact wrenches, that are intermittent use devices, the sandblaster is going to tax you compressor continuously.  That means that you don't want to try to operate a sandblaster that requires more air than your compressor is rated for.  If you do, your compressor will kick on a few seconds after you start blasting and if you keep going, it will run and run, but never be able to keep up and the pressure will fall off.  A bigger tank comressor may help a bit (retard that pressure decline somewhat), but for continuous use, if the compressor pump can't meet the needs of the blaster, it will just make you frustrated.
 

Abrasive

I find it pretty amazing that Eastwood sells silicon carbide for $160/110lbs (plus shipping!), JC Whitney (at least used to sell it) for $160/100lbs, and just up the street from me, next town north, I can buy it for $9/100lb.  A fellow enthusiast named Larry Ditizio years ago did this investigation (Robinsons is the hardware sotre near me that sells it).
 
 

John,

I made some calls and here is the Scoop... Robinson's hardware stills sells the Black Beauty silicon carbide for $7.98 per 100 lb. bag. In
fact they have three grits to choose from: MEDIUM, FINE, and EXTRA FINE, which all cost the same.

They get the stuff from Reed Minerals, owned by Harsco Inc. which has plants in New Hampshire, New Jersey and West Virginia. The
plants also sell the stuff retail at each site. The one closest to me is in Kearny, New Jersey (about 2 1/2 hr. drive). I have relatives that
live about 30 min. from there. I will probably make a family visit and take the sport utility and pick up about 400 lbs. since the plant sells
the the stuff retail for $5.30 per 100 lb. bag.

This is truely a well kept secret if the stuff works like you say it does. I use one of those inexpensive "blast out of the bucket" units to
work on my stuff, but have only used kids play sand which does not work very well.

Anyway, thanks for the info.

Take care,

Larry

For this small scale stuff and the guns you will use for it, get the extra fine grit.  I tried the "fine" and it was too heavy for my gun.

Can you use plain old "play sand"? Yes, but be warned; 1) it is very inconsitent grit size, even filtering with a window screen doesn't help much, 2) it won't "cut" nearly as good at the silicon carbide and 3) DUST!  Tons of it, will go everywhere.  There is lots of dust sized particles in playsand.  There isn't in the silicon carbide.
 
 

Tools and Nozzles

Ok, so back to "How much of a blaster will my compressor run?".  Well, the air passage of a gun is determined by the inside diameter of the nozzle on the gun.  Also note, the suction feed guns (like the blast out of a bucket kind shown below) have air jets behind the abrasive port, and nozzles.  Nevertheless, the air draw is determined by the nozzle, not the air jet.  And note that pressure feed units will draw considerably more air for the same sized nozzle.
 
 

Pressure blasters are the big tank kind where the air supply is used to push the abrasive through (tank is pressurized) as well as expel it out the nozzle.  Suction units are the bucket kind that suck the abrasive up the tube to the gun.  So you can see above that with our single stage, 120 volt compressors, we are relegated to the very lowest end of the nozzle phylum.
 

Safety

Common sense folks.  Use full eye protection (goggles, not glasses) and heavy leather or blasting gloves.  If you think silicon carbide can strip paint off metal easily, wait until you see (and feel) what it can do to skin.

No, don't.
 

So, let's see how to make the "Sand Tub"............
 
 
 
 

Here ya go.  The $7.67 special at Home Depot.  Rubbermaid.

Step one.  Cut a large rectangle hole in the top.  Silicone and rivet a Plexiglas window in.  Tub plastic cuts with a razor knife, 1/8" plexi can be scored and snapped.  If you rivet, do not make the rivets too tight, the Plexiglas will crack very easy, especially at the corners.  I used blind pop rivets, but didn't actually "pop" them.  Just tightened them until snug, released the pin from the tool and tapped the pins out gently.  Plexiglas is very brittle and will crack very easily, especially if point-stressed near an edge.  I put a thin bead of silicone along the Plexiglas edge before fitting it up. I used a 4.25" hole saw (you have one of those, don't you??) to cut access holes on either end, and a 1.25" one to cut an air line hole.  I had just set a gallon bucket of abrasive in there to see how much working room I would have with it in there.

This task was to make a new, shorter suction tube for my blasting gun.  I studied the one that came with the gun and it was clear that the coaxial design allowed an air "let in" at the draw point so it could such media and air to get a flow going.  I scared up some 1/2 and 3/4 copper pipe in the basement and cut it to length with a tubing cutter.  The 3/4" piece is about an inch longer than the other...

I placed the 1/2" tube in the 3/4" tube and with a body hammer, "peened" the tube in two places, to crush it down, and crush the inner tuber slightly, just like the suction tube that came with the gun was made (shown)

Here you can see how the co-axial design allows an air path down into the bucket to where the media is drawn in.

And at the bottom end the 1/2" tube stops a bit short and the outer tube is notched to keep it from "suction cupping" on the bottom of the bucket and stopping flow.

I was testing out how I might use this thing.  Now its first job was going to be blasting parts of a split Beetle "T" air cleaner, a fairly large object.  Trying it out, with my arms in each hole, it became clear that with the whole gun in the tub, I would not have the room I needed to do this piece.  I would need to keep the body of the gun, and the air line outside the tub and "window shoot" the part.  The tub was plenty deep enough though, the 1 gallon bucket at the bottom left lots of room to work.

Ok, we're in business!  No, that is not a small rocket motor, that is the intake end of a split Beetle ""T" air cleaner that is plugged with 10 short pieces of rubber tubing with red Romex wire nuts shoved into the ends of them to make them stopper tight (and keep blasting media out of the filter).  Didn't work by the way, quite a bit of media still got into the filter.  Lots of effort with shop vac and compressed air blow gun to clean it out... The first problem that became evident was that the suction tube in the bucket kept working its way out and "floating up" and out of the abrasive as the tubing was pretty stiff.

You can see here that I cut another access hole in the front.  I found it was easier (at least for this job) to go in through two adjacent sides than opposite ones.  You can also see how much media got blown out through the holes around my hands.  I'm going to get some blasting cabinet gloves for this thing.  Harbor Freight sells these for cheap.

Progressive refinements.  Duct taped my fluorescent drop light to the top (I plan on putting some good bright lights inside under the lid).

Another refinement.  To keep the suction tube from floating out and up, I bolted a couple pinch type clamps to the inside of the bucket.

Copyright© 2002; John S. Henry