Shop built sandblast gun

[OccupantRJ]

I needed a blast nozzle for one of my media blast cabinets, but the cost of the gun from Empire was $155, so I decided to build my own out of materials on hand. The ceramic nozzle is made by Empire, all the rest was shop made. Two inch aluminum round stock was used for the body of the gun, machined, coped, and welded together.

Finger grips were incorporated into the handle of the gun. The nozzle protector is nylon, and the compression ring is steel. An O ring is used in the **** end of the gun to attach the media hose in a compression fashion, by cinching up on the hose when the knurled ring is tightened. This provides a better flow of media from the hose to the inside of the gun. The media hose I use is 5/8 inside diameter automotive heater hose.

Inside the gun is a venturi nozzle that the incoming pressurized air passes through to create the vacuum to draw the media into the air stream inside the gun. This project was a good lathe, mill, and welding project all in one.

 

[bimmer1980]

nice work!!!

 

[zessin]

impressive

 

[jhn9840]

Great job. Beats paying out 155 bucks when yours is just as good if not better.

jhn9840
John

 

[e-tek]

Nice workmanship!

 

[AlchemyMetalworks]

I needed a blast nozzle for one of my media blast cabinets, but the cost of the gun from Empire was $155, so I decided to build my own out of materials on hand. The ceramic nozzle is made by Empire, all the rest was shop made. Two inch aluminum round stock was used for the body of the gun, machined, coped, and welded together. Finger grips were incorporated into the handle of the gun. The nozzle protector is nylon, and the compression ring is steel. An O ring is used in the **** end of the gun to attach the media hose in a compression fashion, by cinching up on the hose when the knurled ring is tightened. Inside the gun is a venturi nozzle that the incoming pressurized air passes through to create the vacuum to draw the media into the air stream inside the gun. This project was a good lathe, mill, and welding project all in one.

RJ...I like your style

I take it the handle started out as larger stock, turning it down between the rings to give you a "grip"...question is, did you offset-turn on the lathe after milling the rings flat on the sides (to get it smooth on the backside) or did you set it up on a rotab mounted vertical, offset the endmill from the small O.D. and mill off the remaining ring-stock while rotating through 180*?

 

[trexdoink]

Very nice.

 

[OccupantRJ]

RJ...I like your style

I take it the handle started out as larger stock, turning it down between the rings to give you a "grip"...question is, did you offset-turn on the lathe after milling the rings flat on the sides (to get it smooth on the backside) or did you set it up on a rotab mounted vertical, offset the endmill from the small O.D. and mill off the remaining ring-stock while rotating through 180*?

Even easier than that. I go straight for the throat, and try not to get too ******* in processes. The rings were simply rough milled off except where wanted, with the piece horizontal in the Bridgeport, then the ending profile was sanded on a 6 inch belt sander, by rotating the handle freehand, relative to the belt surface.

Thinking about that thing, weren't you?

 

[sberry]

Its nice, did something similar,

 

[OccupantRJ]

Its nice, did something similar,

sberry, if you were to change the T fitting to a wye fitting, it may suction media better, due to the more acute angle. Does it work pretty well as it is?

 

[zessin]

just curious could/does the sand/air going through the gun and hoses wear down everything eventualy pitting or making holes?

 

[sberry]

Yes, it works quite well, use it as an air vac too, have field made something similar with rubber hose and blow gun. It was a quick deal off the shelf parts, took about 20 minutes, I think I had some sears thing and it broke so I sling that together. Vacuumed some water from the bottom of a fuel tank the other day, I could see it in there with flashlight, was outdoors so blew it outside, could vac the drops of water right out of the bottom, saved removal and draining tank.

 

[sberry]

I could change nozzles depending on volume of air supply. The original poster's bas a lot more curb appeal though, same principle.

 

[OccupantRJ]

just curious could/does the sand/air going through the gun and hoses wear down everything eventualy pitting or making holes?

Yes, in theory it should wear out quickly, but I have a similar cast aluminum blast gun at work that has been in use with glass media for 30 years, so at my age of 58, maybe I'm good.

 

[OccupantRJ]

Yes, it works quite well, use it as an air vac too, have field made something similar with rubber hose and blow gun. It was a quick deal off the shelf parts, took about 20 minutes, I think I had some sears thing and it broke so I sling that together. Vacuumed some water from the bottom of a fuel tank the other day, I could see it in there with flashlight, was outdoors so blew it outside, could vac the drops of water right out of the bottom, saved removal and draining tank.

Good idea on using the device as a vacuum drain.

 

[cnc-me]

Very nice job.

 

[IndyGarage]

Very nice work.

I can appreciate fine craftsmanship, however I personally would have way more than $155 in labor ******* in making something that nice. The tig weld alone would make it cost prohibitive for a production shop.

Sberry's looks like the money saving design for me.

 

[sberry]

I can understand making one as nice as occupants is, had the ability/time/materials, a huge factor. Wouldn't be worth the effort to tool up to do it.
I don't have machine tools but my neighbor has a couple things for the crisis I really need to use them, most things in life I can work around anymore, having die grinders, etc and huge supply of material and I can find something that will do about 99% of the time. I can live without that stuff, just more tooling kicking around, if I needed it I would certainly have but MyGyver is an amateur compared to me. Supply chains are so good anymore too, not like back in the day when stock and procurement was difficult. Its hard for me to turn a bushing I can buy for 4$ that fits the app.
I probably wouldn't have a tig except I got it for 200 and I have about 10 miles of aluminum pipe, build custom fittings and repairs but lately the tig has taken a back seat to the HH210 and spool gun.

 

[sberry]

Sucked water out of a tire casing with that the other day, I have a couple of them. I don't always strictly copy the design of the factory when doing something like that, usually tend to follow the general principle.

 

[SBOhio]

New to media blasting and in a previous post RJ mentioned the gun was one of the keys to a good system. I had a chance to try a cabinet out for the 1st time yesterday and it was terribly slow. HF with glass beads and the gun kept quitting. Can you guys elaborate on what makes a good gun different from a poor one and what I should look for? Also can you elaborate on the venturi and its placement?

 

[OccupantRJ]

Any blast gun without a trigger is a good one to me! I hate holding the trigger while blasting. Foot pedal or foot switch solenoid is much better IMO. By not having to hold the trigger, the gun can be turned and twisted for weird angles more readily. My gun has the capability to change out air jet sizes, as well as the nozzle size, and the air jet can be adjusted back and forth relative to the nozzle to adjust venturi effect. I guess if a guy was creative, he could measure and adjust the suction of the gun while air was being applied, using a manometer or possibly a vacuum gauge. I might have to give this a try.

Edit: I have since used a vacuum gauge attached to the media port of the blast gun. The reading was 5 inches of vacuum initially. After a couple of fore/aft air jet adjustments, the vacuum went to 14 inches. Abrasive flow increased. A win!

A major factor is the introduction of inlet air mixed with media in the right proportions. The cabinet design has much to do with this. If a tube is extended down into a batch of media, it will tend to get an uneven flow of abrasive to the gun. The use of a hopper bottom with a media outlet underneath, along with an outside air inlet will tend to smooth things out.

There is usually a 90 degree pipe fitting with a hole drilled into the side of it under the cabinet hopper. The suction hose is inserted into this fitting and adjusted in or out to expose more or less inlet air, and held in place with a thumb screw tapped into the side of the fitting. This allows you to adjust the ratio of inlet air to media flow. All this applies only to suction type cabinets, pressure cabinets are a different animal.

Edit: Found an old picture of my media port. The suction hose slips inside this fitting, and is adjusted in or out to expose the hole to outside air, to adjust the air/media mix. A sand carburetor, if you will. The smaller fitting was where I experimented with an air jet inside the fitting to see if it helped the flow of media. That's been so long ago that I don't remember the results.

 

[KMinAF]

does the length of the pick up hose have any affect on the siphoning? I have the smaller HF cabinet that uses a short piece of tubing buried into the media.

 

[KerryH]

I have a home built blast cabinet and I'm very interested in ways to get better performance from it. It's using a syphon gun from tractor supply and I just have a typical 60 gal ~5hp compressor. Currently the performance is pretty dismal.

 

[OccupantRJ]

A gun cannot **** a hose full of grit. There is just not enough suction. The heavier and coarser the grit, the worse this situation is. Air must be flowing through the suction hose at all times that the gun is being used, with the grit (media) allowed to flow into the air stream in the right air/media proportions to be transported through the hose. Note: This is the major function missing from a lot of suction systems.

In a cabinet where the media is sucked out of the bottom of the cabinet, voids occur around the end of the suction hose, and the gun loses material. Opposingly, when the end of the hose is buried in media, there is no air flow to the gun, so grit movement stops.

The magic here is to dribble media into that air stream at a constant, regulated pace. That is where the feed fitting comes into play, accepting gravity fed media from the bottom of the cabinet or reclaimer, then allowing enough ambient air to enter to provide the proper mix to the gun. The sharp 90 degrees of the fitting stalls the media from free flowing too freely and clogging the suction hose.

A trick to try the next time your SUCTION media gun clogs is to stop blasting, place a gloved finger over the gun nozzle to seal it off, then give a short burst of air to the gun. This will backfeed air down the media hose to help clear it of grit and get the proportions of air to grit back in line. Also having a piece of metal tubing with a 45 degree cut end on the suction hose will hold the end in the media, and can also act as a metering device to help prevent clogging by allowing inlet air. Not foolproof, but can help in some situations.

 

[SBOhio]

Any blast gun without a trigger is a good one to me! I hate holding the trigger while blasting. Foot pedal or foot switch solenoid is much better IMO. My gun has the capability to change out air jet sizes, as well as the nozzle size, and the air jet can be adjusted back and forth relative to the nozzle to adjust venturi effect. I guess if a guy was creative, he could measure and adjust the suction of the gun while air was being applied, using a manometer or possibly a vacuum gauge. I might have to give this a try.

A major factor is the introduction of inlet air mixed with media in the right proportions. The cabinet design has much to do with this. If a tube is extended down into a batch of media, it will tend to get an uneven flow of abrasive to the gun. The use of a hopper bottom with a media outlet underneath, along with an outside air inlet will tend to smooth things out.

There is usually a 90 degree pipe fitting with a hole drilled into the side of it under the cabinet hopper. The suction hose is inserted into this fitting and adjusted in or out to expose more or less inlet air, and held in place with a thumb screw tapped into the side of the fitting. This allows you to adjust the ratio of inlet air to media flow. All this applies only to suction type cabinets, pressure cabinets are a different animal.

Edit: Found an old picture of my media port. The suction hose slips inside this fitting, and is adjusted in or out to expose the hole to outside air, to adjust the air/media mix. The smaller fitting was where I experimented with an air jet inside the fitting to see if it helped the flow of media. That's been so long ago that I don't remember the results.

Now we're getting to the nitty gritty of how these things work. What size pipe is your 90 fitting? Are you saying the small hole on the left is tapped for the set screw? What size pipe ****** did you use to go into the 90? Does the 45 degree cut on the ****** you refer to in a later post end up under the air hole or farther in 90? Or is it placed on the vertical leg of the 90 inside the hopper?

 

[OccupantRJ]

I think you may have confused two different methods of drawing media.
The first is simply a suction hose from the gun into media inside the lower part of the cabinet. Next possible refinement is a piece of metal tube with a slash cut end inserted into this same tube.

Next method is the 90 degree shop built fitting, which can be used under a cabinet to catch gravity flow of the media. This is also used underneath a reclaimer for the same purpose. The two methods are not used together. Either you **** media from inside the cabinet, or you catch it underneath the cabinet by gravity feed.

My fitting is a piece of 3/4" pipe ******, cut in half at a 45 and welded to form the 90. A setscrew threads into the small tapped hole to hold the hose in position. The hose can be adjusted in or out to open or close the larger hole on the upper side, which will determine your air/media mix. Close it off, no media flow to the gun because the media clogs the hose. Open it too far, less media to the gun, more air.

The pic in post 21 shows the fitting screwed into the bottom of my reclaimer hopper. If no reclaimer is used the fitting would attach to the bottom of the cabinet hopper itself.

Look at the following threads for more pics of my reclaimer and how the media is fed from it.

http://www.garagejournal.com/forum/showthread.php?t=121914

http://www.garagejournal.com/forum/showthread.php?t=124933

 

[OccupantRJ]

does the length of the pick up hose have any affect on the siphoning? I have the smaller HF cabinet that uses a short piece of tubing buried into the media.

I feel that the shorter the better, but you need enough to allow you to reach all areas during blasting without pulling the hose up out of the media.

 

[KerryH]

A gun cannot **** a hose full of grit. There is just not enough suction. The heavier and coarser the grit, the worse this situation is. Air must be flowing through the suction hose at all times that the gun is being used, with the grit (media) allowed to flow into the air stream in the right air/media proportions to be transported through the hose.

In a cabinet where the media is sucked out of the bottom of the cabinet, voids occur around the end of the suction hose, and the gun loses material. Opposingly, when the end of the hose is buried in media, there is no air flow to the gun, so grit movement stops.

The magic here is to dribble media into that air stream at a constant, regulated pace. That is where the feed fitting comes into play, accepting gravity fed media from the bottom of the cabinet or reclaimer, then allowing enough ambient air to enter to provide the proper mix to the gun. The sharp 90 degrees of the fitting stalls the media from free flowing too freely and clogging the suction hose.

A trick to try the next time your SUCTION media gun clogs is to stop blasting, place a gloved finger over the gun nozzle to seal it off, then give a short burst of air to the gun. This will backfeed air down the media hose to help clear it of grit and get the proportions of air to grit back in line. Also having a piece of metal tubing with a 45 degree cut end on the suction hose will hold the end in the media, and can also act as a metering device to help prevent clogging by allowing inlet air. Not foolproof, but can help in some situations.

Wow, seeing this put into words makes so much sense. I have the hose for my siphon gun just buried in the media, and I've noticed that it sort of "pulses" the media as it's fighting to get media and air. I've also noticed that sometimes if I let the media get low, the suction from the hose will form a crater and a void of media will be created, however the small amount of media that is being sucked in from the edges the gun works amazingly well at that time but not for long.

I think I need to try out a 90 degree fitting now.

 

[chris fresh]

Awesome amounts of info for all of us Occupant.Since i'm building from scratch at the moment,i'll be using the 90 degree trick.I'm guessing i'm gonna go with the pedal set up,the 90 fitting and draw off the bottom,and i haven't decided on gun yet.I care and don't care about the money for the gun because as soon as it works how it should,i don't care if the gun was 300.Lol

 

[OccupantRJ]

If you attach the media fitting to a small "trap door" that is easily removed from the bottom of the hopper, you can make media changes easily. Mine is held on with two suitcase latches, and feeds the large extraction hose. Also, if you want to experiment with other methods of media withdrawal, it is easliy changed. After thinking about it, on my fitting, I was going to insert a piece of steel tubing into the plugged opening on the right. This was going to protrude past the draft opening a few inches Into the grit suction hose to introduce low pressure air. This would theoretically induce a suction closer to the media drop to assist the existing suction at the gun.

About this time is when I found a better gun than the one I was attempting to use, so never pursued it further. The gun in this thread was made for my larger cabinet.

 

[OccupantRJ]

Awesome amounts of info for all of us Occupant.Since i'm building from scratch at the moment,i'll be using the 90 degree trick.I'm guessing i'm gonna go with the pedal set up,the 90 fitting and draw off the bottom,and i haven't decided on gun yet.I care and don't care about the money for the gun because as soon as it works how it should,i don't care if the gun was 300.Lol

The less media you can keep in the hopper bottom of the cabinet, the better, as long as there is enough to constantly keep the gun fed. Dumping large amounts in will just allow the weight of the media to compact the media at the bottom, possibly causing it not to run freely into the mixer 90. This is the main reason air going to a blast cabinet needs to be dry, to prevent clumping of the media, and of course, to prevent moisture being deposited on your part.

 

[chris fresh]

Funny you say this,i was just thinking about the gravity feed issue.I was thinking about your set up with the plug on the left,i was thinking,what if you were to introduce air tot hat side with a small valve to regulate flow.This would definitely assist in pushing media up to the gun.

Secondly,The trap door.I know in my current cabinet,i had an issue with paint chips getting sucked up and clogging the gun.So i ended up making a basket for the end of the pick up tube made out of vinyl window screen.This helped tremendously.

But for the new cabinet,i'm going a different way.I'm going to do the bottom gravity feed,copying your tube design.I will also build a square frame to sit in the bottom of the hopper.This frame will have screen across it to catch anything that could possibly make it to the pick up tube.There will be a trap door in the side of the hopper to be able to clean out the screen.

 

[chris fresh]

The less media you can keep in the hopper bottom of the cabinet, the better, as long as there is enough to constantly keep the gun fed. Dumping large amounts in will just allow the weight of the media to compact the media at the bottom, possibly causing it not to run freely into the mixer 90. This is the main reason air going to a blast cabinet needs to be dry, to prevent clumping of the media, and of course, to prevent moisture being deposited on your part.

Less media in the hopper is definitely the way to go,i recently cleaned mine out and just put in enough to supply the tube and it worked WAY better than a whole bag or two like i use to do.

Even though being in the south and the humidity is usually through the roof and my shop is not climate controlled,damp media has never been an issue.I use DuPont StarBlast media,maybe it's an issue with other blasting grits,but not mine.I have heard of guy's leaving their light on round the clock to keep a box warm/dry though.

 

[OccupantRJ]

Funny you say this,i was just thinking about the gravity feed issue.I was thinking about your set up with the plug on the left,i was thinking,what if you were to introduce air tot hat side with a small valve to regulate flow.This would definitely assist in pushing media up to the gun.

Secondly,The trap door.I know in my current cabinet,i had an issue with paint chips getting sucked up and clogging the gun.So i ended up making a basket for the end of the pick up tube made out of vinyl window screen.This helped tremendously.

But for the new cabinet,i'm going a different way.I'm going to do the bottom gravity feed,copying your tube design.I will also build a square frame to sit in the bottom of the hopper.This frame will have screen across it to catch anything that could possibly make it to the pick up tube.There will be a trap door in the side of the hopper to be able to clean out the screen.

I think the screen is an excellent idea! On the reclaimer/cyclone separator type system, the travel of the used media through the large draft hose into and around inside the cyclone seems to break up and discharge paint particles into the nuisance bag, and so far I have seen no need for a screen.

However, on my larger cabinet I may have to try one as that cabinet will be using a much more aggressive grit for cleaning rust and paint off objects. I have relegated the smaller cabinet to glass beads only, so any paint particles are likely relatively small.

 

[chris fresh]

Yeah at first i only had a piece of screen layed flat on the mesh,it helped but paint chips always got around the edges and managed to make it to the pick up tube.Then i dumped all the media and figured while it was empty,it was time to bag the pick up tube.It is the single best thing i've done since i've owned it.

But i think with the new design,and pulling off the bottom of the hopper,the screen will be more than fine and will constantly screen the media falling back to the pick up.It's weird,i never noticed what accumulates in the media until you screen a bucket of used material,some crazy stuff in there.

 

[chris fresh]

Now if i use your 90 fitting design and feed the back side with low volume air to "push"media toward the gun,then i technically don't need the air hole to draw in,correct?

I'm thinking of design,Meaning if i push media to the gun with air,then i might be pushing it out that hole if i kept that hole.

Or,keep that hole to draw in and still use air,but introduce the air after the hole.this way it's pushing and that hole is now vacuuming,if that makes sense.lol
Hard to explain exactly what i mean

 

[OccupantRJ]

Now if i use your 90 fitting design and feed the back side with low volume air to "push"media toward the gun,then i technically don't need the air hole to draw in,correct?

I'm thinking of design,Meaning if i push media to the gun with air,then i might be pushing it out that hole if i kept that hole.

Or,keep that hole to draw in and still use air,but introduce the air after the hole.this way it's pushing and that hole is now vacuuming,if that makes sense.lol
Hard to explain exactly what i mean

Not really, I got it fine. The last method was what I was thinking of trying so that a vacuum is pulled at the draft hole, as well as pulling on the media to assist it getting to the gun. It would need to be fed from the same valve as the gun to activate only when the gun activates, or you would get air out of the gun at all times. I think it would also need to regulated to a low psi, just enough to do the job.

This has been a "blast" discussing this today! Hopefully someone will get some good use out of the information presented, that will help them in their endeavors.

 

[chris fresh]

Not really, I got it fine. The last method was what I was thinking of trying so that a vacuum is pulled at the draft hole, as well as pulling on the media to assist it getting to the gun. It would need to be fed from the same valve as the gun to activate only when the gun activates, or you would get air out of the gun at all times. I think it would also need to regulated to a low psi, just enough to do the job.

This has been a "blast" discussing this today! Hopefully someone will get some good use out of the information presented, that will help them in their endeavors.

I'm going to try some different options,the gravity feed is definitely the way i'm gonna go.I see what your saying about the gun regulating air flow and being on all the time.I should of clarified,

I'm thinking this,

Bring the air supply into a pedal set up,come out of the pedal and split the line.One line runs to the gun as normal,the other line runs to the 90 fitting in front of the draw hole.This way the air is pulling through the draw hole,then pushing product to the gun.I realize it would be to much pressure to run wide open to the 90,so personally i make a fitting here also.The fitting would come out of the bottom of the 90,run straight to the feed hose just like yours,and the air inlet would be angled back at say a 45 degree angle to help promote air flow toward the needed direction.Lastly i would use a small (maybe 1/4 ) ball valve to control the flow rate of the introduced air.

Only thing I'm on the fence about is the hole for air in the 90 fitting.If you were feeding the "system" with air,would it really be needed?


Thanks for all your time on this man,I really appreciate the time and info and i agree,hopefully this will answer and help a lot of other guy's questions.I'm just trying to build the best box for me,and to save other people some leg work.

 

[OccupantRJ]

I think the hole would act as a modulator to equalize the air flow differences between the two air flows.

 

[Big_Ben]

I have purchased nozzles and media from IDS Blast. If you have questions or need OEM replacement parts look them up idsblast.com. I spent a hour just looking at all goodies they had. Just my $.02.