HF Sandblaster Metering Valve Build - Part 2

In this episode I finish the last few operations of the DIY metering valve and show the assembly. I also carry out some tests which show some improvement over the standard pickup tube supplied with the blast cabinet. If you want to go straight to the testing, go to 15:40 Still, it's not a total solution and I have started on a new blast gun design which might give me a continuous supply of media to the part.

[@mrdr9534]

@Mark Presling You might feel a bit "peeved" about missing the fact that You could have bought the parts instead, but for us who got to see Your videos it was "all win" :) Thanks for taking the effort of recording and sharing. Best regards

[@devonty3647]

I guess Im kinda off topic but does anybody know of a good site to stream new movies online?

[@abramkaysen4684]

@Devon Ty Flixportal :)

[@devonty3647]

@Abram Kaysen thank you, I signed up and it seems like a nice service =) I really appreciate it !

[@abramkaysen4684]

@Devon Ty Glad I could help =)

[@dimtt2]

I have made myself a metering valve out of 1'' pipe fittings(a tee fitting,a pipe plug, a straight pipe section, a 1''-1/2'' reducer and a nipple for the hose. The metering part is machined and welded to the straight pipe). It works well together with a Chinese gun I bought from Ebay (China). Added bonus is that the gun includes a boron carbide nozzle for ridiculously cheap money. And I can verify that the nozzle lasts. I have been using it for 2.5 years with glass beads and there is no perceptible wear on the nozzle. If anyone wants the link to the gun let me know, I don't want anybody to think I'm advertising for the seller. Anyway I have a tip for you since you are going to make your own gun. I bought the above gun which came with a boron nozzle and I bought an extra nozzle of a different size. The extra nozzle came with an extra air jet that has a different orifice size. The air jet is the machined steel part that fits inside the gun and spits the pressurised air right behind the nozzle creating the vacuum that sucks the media. In my case the air jet for a 5mm nozzle is 2.5mm. And the air jet for a 6mm nozzle is 3mm. I believe that the size of the orifice is significant compared to the nozzle size. I don't have a rule but the above work well for me ever since I added a dehumidifying filter to my air supply. (Before that the air jet rusted rather quickly so I made new air jets out of 303 stainless copying the original dimension,s most notably though the gun would clog full of ice after continuous use for more than 10minutes). Now with dry air the whole system works well.

[@jonknight9048]

link to the gun please

[@dimtt2]

@@jonknight9048 www.ebay.com/itm/C1-Spray-Gun-Kit-Sand-Blast-Gun-Kit-with-1-Boron-Carbide-Nozzle-L35mm-Free-Ship/332015218001?hash=item4d4da62d51:g:gBUAAOSwUYNaFrZK Like I said i got the 5 and 6mm nozzles. You need a big air compressor to go much above that. My 3kW-4hp unit barely keeps up with the 6mm nozzle-air jet setup at 6bar-87psi

[@jonknight9048]

@@dimtt2 Many thanks I have a 3kw 17cfm compressor

[@Preso58]

Wow, that's interesting. I would appreciate the link for the gun. I have the two ceramic nozzles that came with my stock gun but I don't like the fact that I can't really modify them. I have watched a guy from a channel called Arnold's Designs. He makes a living sandblasting and vapour blasting motorcycle parts and he uses tungsten carbide nozzles that he buys off the shelf from McMaster Carr. I don't have that option here in Australia but he has also made nozzles from hardenable steel and left them fully hard. It's interesting to hear about your experience with different mods and I am hoping to do some tests today with jet sizes similar to what you have used. I was going to start at 2mm and then gradually open it up 0.5mm at a time and measure the vacuum with a manometer. OK, scratch the request for the link, I just found it on your second post! I also found the link for the spare nozzles. $14.50 US. That's like $20 AU but at least it's free shipping. Regards, Mark

[@johngurney1069]

Hi Mark thanks for reply came across company that sells valve they recommenced a kit that has hoses gun and other parts needed for satisfactory results, yes maybe media is the problem. spent 2 days working on this , gave up put it back as it was , bought a new gun and happy with results ,very cheap but works better then expensive gun i purchased sometime ago, nice talking to you regards john

[@lv_woodturner3899]

A lot has been learned so far, some positive some not so positive, but all useful knowledge. Another cliff hanger. LOL Dave.

[@Preso58]

Dave, wait till you see the next one 😥 More bittersweet results....

[@mclem4u]

“ Keep on keepin on “ Mark. Can’t wait to see how the new gun works.

[@Preso58]

I am hoping to start doing some experiments with it today. I am going to do the full "Mythbusters" on it. I have a rig that can measure the amount of vacuum, sort of a crude manometer, but it should allow me to experiment with different jet designs to optimise the design. Regards, Mark

[@theonlybuzz1969]

Looking forward to seeing some of your results like everyone on here, I get what you mean over the whole idea of making something for you that you can be proud of, only to find after all the heartache, a shop near to you stocks this. Typical, just suck it up and put it down to experience, for if you hadn’t done that, then there could have been a lot of us doing the same problems, thanks again for your work on KZbin.......Phil

[@Mrelectric423]

I dont regret that you made the valve and great video, Thank you!

[@Preso58]

I found out later that you can buy that metering valve but I learned a lot from making my own. That's the added bonus of making your own tools and devices. Regards, Mark

[@theonlybuzz1969]

The tap wrench is sizeable, I have had to make ours and end to end 600mm long, we then ave another 300mm added to try to make the tapping easier, I was tapping 12 off x 1” BSP by 15mm wall thickness of aluminium. I started it off and had a lift from one of the lads to get through them. Keep up the great work....Phil

[@pgs8597]

G’day Presso, nothing like spending the money to find out it needs modifications, good luck with a fix. Cheers Peter

[@allengentz7572]

Keep at it Mark persistence will pay off,and besides I am interested in your platform as it contains material that I can use.

[@infoanorexic]

I had one, years ago, that used that aspiration tube. It worked just fine at 90 psi, so I think you could be right about the gun. It did give a heavier burst of media at the beginning of the blast, after that it delivered at a consistent rate, without the hiccups you demonstrated. The supplied gun will still be useful. I used mine for back flushing radiators and heater cores. Garden hose hooked up where the sand normally came in, nozzle hooked (adapted) to the lower or "out" hose of the unit. Let them fill, then give them a burst of air to shock the settled in crud loose. I've cleared out heater cores that had become clogged up from the use of Silver Seal or Barr's Leak that way.

[@Preso58]

I was doing some test with the original gun yesterday and I was really surprised at how high it could lift water. At just 20psi it lifted water from a bucket nearly two metres vertically. I then ramped up the pressure to 80psi and it was like a pressure washer. I am hoping to do some tests on my new gun using the same rig. It's technically a manometer but it's really just some plastic tube strapped to a piece of conduit. If I keep the pressure fixed I can measure how far the water column rises and then play around with different jet designs to see which works best. Stand by for some pseudo science. 😁

[@infoanorexic]

@@Preso58 I wasn't impressed with the result I got when I tried it for pressure washing. It did work great for spreading soapy water over the object, but it wasn't much for blasting the crud away. Still, if your cleaning agent is on the caustic side, that could help get it to where it would be difficult by other means, without the risk of getting it on your hands.

[@Steve_Just_Steve]

Hey Preso, another great build! On that stainless, prob 17-4PH, at any rate it's probably not more speed you need, but rather more feed. In my experience you've got to really give er' the feed (14-20 thou per rev) to break a chip on that stuff. ATB Steve edit: oh and coolant helps me a lot on SS =)

[@PeteBrubaker]

I must agree Steve, you're spot on. Feed is what's needed. Also the particular insert he was using isn't going to do the job. That's a high positive insert designed for aluminum - a CCMT insert designed for steel with a higher feed (like you suggested) will produce nice chips. Mist coolant helps a ton too!

[@Preso58]

Peter. You are correct, it was an insert I purchased for aluminium but my lathe is woefully underpowered. It originally came with a 7HP three phase motor and I don't have three phase so I replaced it with a 1.5HP single phase unit. At the time I had very little spare cash and it was all my budget could stand. I have run CCMT inserts at the speeds and feeds close to what they need and stalled out my motor. That aluminium insert was giving me a good finish at the speed my lathe could manage. Some time soon I will get a bigger three phase motor and run it from a VFD. I just have to convince my wife that it is a "necessary upgrade consistent with quality assurance" 😁

[@PeteBrubaker]

@@Preso58 I totally understand budget constraints Mark, good luck on that new motor and VFD! It'll be like a whole new lathe!

[@yvesdesrosiers2396]

G'day Mr P. You know it is not the size that matters but how you use it. The tap wrench of course.I have a small bench top model that does the same. That is why I want to build a new one. Looking forward to the next one. Thanks for sharing and nice job. Cheers.

[@Preso58]

Yes, my wife was always commenting about how small mine was so....😁

[@MusicalMikeTube]

It looks as though the bore of the tubing is too big, it's trying to pick up too much media for the air pressure to handle. You could try a smaller bore tube. Possible problem here is clogging of the tubing. Higher pressure to be able to pick up more media? How about 2 media hoppers, one underneath to collect used media and one higher up for the feed. Adjustable height might be a good idea for fine tuning.

[@Preso58]

Mike, since completing all the upgrades on the sandblaster I have come to the conclusion that my compressor really needs to be replaced. It is over 25 years old and it was only ever intended to run a nail gun. I am also considering fitting a pressure pot type blast unit mounted on the wall above the enclosure. Space is very limited in my shop so I can't really leave the pressure pot at ground level. The upgrades I have already done do improve the efficiency but there is still a lot of room for improvement. I am currently overseas on a holiday and when I return I still intend to make the clear blast gun so I can visualise what is happening inside the body of the blast gun itself. Regards, Mark

[@bobvines00]

Mark, Even though this wasn't a total "fail," you still learn a lot from failures, just like "wins." I'm really looking forward to the following video to see what you come up with (along with the new gun) to make the cabinet actually work. What kind of "ventilation" does the cabinet have? The big walk-in blast cabinets here at work have filters on the doors to let the cabinet suck air in. Maybe your cabinet is suffocating?

[@Preso58]

Bob, I left the big port on the left side of the cabinet open to atmosphere and the suction for the dust extractor comes from a slightly smaller port on the back wall. I am beginning to suspect that the metering valve could benefit from some forced air rather than just relying on natural aspiration. I am doing some experiments at the moment with the new gun and I am just off to the hardware store shortly to see if I can get a compact regulator to run a second low pressure air line to the metering valve. The video of the gun casting is going up today. Spoiler alert.... it didn't go as planned. 😥

[@_bodgie]

I wonder if a smaller diameter media delivery hose would help?

[@The_fappening]

Same, small diameter high velocity

[@kenny5174]

Great video!

[@michaelcook3542]

i have the tacoma gun makes a big difference i have the pedal assembly really nice option

[@Preso58]

Most people who have purchased the Tacoma kit seem to be very happy with it. My compressor is getting a bit tired in it's old age and I am keen to see if the new gun design can reduce the air consumption. I am starting some tests on it today to try to optimise the jet design. Regards, Mark

[@1957kwick]

The media may be damp as well.🛠

[@TheDgdimick]

I would have drilled the hole first, then sized and threaded it, there has to be a GOOD reason he didn't do it that way. Wonder what it is.

[@user-A-A-RON]

You want to almost have the air intake on the metering valve closed instead of wide opened.

[@Preso58]

In reality, it doesn't seem to have a great deal of influence over how the media is drawn up into the gun cavity. It still surges but the media is delivered from the nozzle at almost a constant rate. Regards, Mark

[@HavaCrack]

Good video and build. I have the same hafco sandblaster and they are rubbish in the condition they are sold. Mick

[@Preso58]

Sad but true! I have mine working OK-ish now but what you start out with is really just a sheet metal kit. Regards, Mark

[@HavaCrack]

Mark Presling Based on your info and you making your own metering valve, I machined a metering valve from aluminum with an internal taper and a length of about 90mm (not sure if measurements makes a difference). Then bought the mod-u-blast gun from hafco and dropped my psi from 90psi to around 45-50 psi, aside from a biit of moisture in the line it works great now or how I would expect it should have worked. Maybe I should have tried the original siphon tube at 45psi and not thinking more psi was better. Yes hafco should just sell the cabinet as a cabinet and market that they have thrown in a free gun that may not work. I would recommed that anyone in Australia who buys the hafco cabinet to buy the metering valve and gun and not waste time with the supplied siphon gun/tube. Regards Mick

[@sys2]

Hmm, how about the tube being to big for the amount of air the gun is pulling? looks like when it creates a "plug" then it shoots up the tube .. tried with a smaller pickup tube? =)

[@Preso58]

I have not tried a smaller pickup tube. However, I have found that even though the delivery of the media from the hopper to the gun is not continuous, it still seems to eject the media from the nozzle in the gun in a continuous stream. I think the internal cavity inside the gun is able to hold sufficient reserve to allow it to be ejected from the gun at a steady rate. Regards, Mark

[@sys2]

@@Preso58 aight, having big problems with my cabinet so yesterday i inserted a 4mm tube like 1 or 2 inches up the suction hose at the metering valve and put a small pressure there to help the flow, worked like a charm .. geting good consistent flow now :) drilled from the back and just let it lay in the hose :)

[@crazyfeller5704]

I have a portable blaster that works tremendously better with very dry sand. Wondering if the moisture content is as much problem as the mechanics? Wonder if installing a small vibratory motor on the valve would assist with keeping the sand and air mixture agitated? My kid plays too much Xbox, and goes through controllers frequently as they are crap. Had them apart several times for repairs, each has two small vibrating units for that actual “combat feel”. I would imagine you know someone that has a youngster with a few broken units you could salvage parts- free stuff to give it a try. As always, really enjoy the content. Thanks for sharing.

[@crazyfeller5704]

I was thinking of adding something to the outside of the valve, just clamp it on. No doubt it would suffer a quick death inside the chamber. Perhaps holding a palm sander against the valve would see if it is even viable.

[@Preso58]

Adding vibration would be a good way of fluidizing the grit. I would love to experiment with adding low pressure but high volume air from the bottom of the hopper to double the volume and halve the density of the grit. We had a fluidizing tank at school for hot dip coating steel. We used a vacuum cleaner in reverse to create the air supply and you could literally see the powder double in height when you turned the blower on. If you put your hand in the powder it felt like water!

[@bobengelhardt856]

@@Preso58 Or, how about adding pressurized air at the back of the metering valve? I.e., shooting air down the taper. Not only fluidize the media, but give it some velocity too.

[@metalworksmachineshop]

Impressive,

[@MrFlashx1]

Maybe that delivery pipe is a bit large

[@Preso58]

It's all a mystery! I am still struggling with trying to understand the physics or what is going on. I am starting to run some tests today using a DIY manometer to measure the vacuum. However sand and grit behaves quite differently to liquids like water.

[@jamest.5001]

Instead of allowing air in, why not supply compressed air , like about 30 psi with maybe a foot pedal to introduce air,

[@Preso58]

I really wanted to avoid using compressed air. Generally you won't get enough volume of air to support full combustion of the fuel using compressed air. You get lots of velocity but not volume. A lot of furnace burners use compressed air to atomise the fuel, especially if it's waste motor oil but you still need a blower as well. Regards, Mark

[@stevecallachor]

To make chips you need feed not speed!! Stavros

[@stank9203]

Have you sorted the blast media flow problem I’ve encountered the exact same and am left scratching my head

[@Preso58]

I will be doing some serious testing of the gun and the metering valve tomorrow. I intend to tabulate all the results and put it up on the next video. I have made a sort of crude manometer so I can measure the suction created by the gun compared to the original one supplied with the blast cabinet. If I can get say, a 75% increase in efficiency I will be happy but I doubt that I am ever going to get a fully continuous supply of garnet. I think my compressor is getting to old and it already struggles to keep up with the demand of the gun.

[@CapeCodCNC]

cool!

[@bainmeister1]

Do you have to switch to a pedal activated blasting gun when you use a metering valve?

[@Preso58]

No, you can still use a trigger on the blasting gun. The metering valve is just an attempt to make the blasting media a little less dense so it gets drawn up towards the blast gun more easily, Regards, Mark

[@HTHCLLC]

Funny, what you call a spanner we call a Arkansas socket set.

[@PeterFeltersnatch852]

Now if I only had a probe and a lathe I'd be all right I guess? 🤔

[@dan5her]

Hey Mark, out of curiosity, what do you think of a gravity feed system? larger hopper on top of the unit filled with garnet? I have a similar unit that i got from super cheap, when i try run it on 30/60 garnet it gets clogged up easily, but also has the fits and starts like your having cheers

[@Preso58]

DSRmoto, I am thinking about buying a pressure pot and just using the blast cabinet as an enclosure to capture and recycle the grit. Trade tools sells a fairly compact one and I am thinking I will mount it on the wall above the blast cabinet. It just means that you have to physically transfer the grit every now and then. www.tradetools.com/product-range/machinery-and-workshop/sandblasters/renegade-industrial-10-gallon-pressurised-sand-blasting-tank

[@dan5her]

@@Preso58 If you end up doing that, please post a video, id be keen to see how it works out for you! also, enjoy your holiday, i spent 4 months in europe last year, was a great experience

[@dan5her]

actually, you should make one, out of a 45kg gas bottle! could make an interesting video?

[@scummyinoz]

Gday not bad i got the same blaster but my pickup tube has 2 and bolted on the side of the box1 is a breather the sand comes out in glugs thats what i call it. on the 2nd tube i put a air line and tap of the air line to the gun to whats the name for it mmm to fluff up the sand (grit) to try and make it feed better and it did help to the point that it was more usable then in the stock form but always looking for improvements i looked at the tacoma stuff nothing on his web site or his ebay so to hard thanks and cheers

[@Preso58]

Well, great minds think alike and all that. I was thinking along the same lines with regard to introducing pressurised air into the pickup. I am thinking I could run a second regulator with a relay operated air valve so that I could inject some low pressure air into the metering valve directly. I wonder why some people end up with different patterns of pickup tubes? I had seen the pickup tube that you are describing and I assumed that was what I would get from Hare and Forbes. The one that you have would certainly be less obtrusive inside the cabinet.

[@EDesigns_FL]

@@Preso58 You can add a port to your gun to get the air you need for pressure assist feed. The only down side to this method is that you will have an extra air line running to your gun. You don't that much air flow; a 6mm air line should be sufficient.

[@scummyinoz]

is there a way to send u a pic?

[@johngurney1069]

hi i made a valve also had same problems tried 3 different guns still no improvement going back to original set up wasted time and money for no improvement

[@Preso58]

John, I was expecting much better results after making and fitting my metering valve but the improvement was marginal. I am wondering if the media that I am using has anything to do with it. Some videos that I have seen (like Keith Rucker's) show that he is using very fine media like beach sand. My garnet is more like coarse river sand. Keith showed that adjusting the air inlet on the metering valve made a difference in flow. However, I am still happy with the overall performance of the blast cabinet, the metering valve and the new gun that I made. I don't do a great deal of blasting so it's OK for occasional use.

[@sparkyinanissan]

It's all about the journey, as they say. If your not going to make it yourself, or at least try, why bother having all the tools?

[@Preso58]

That's what I keep telling my wife! 😁

[@tantrinh4754]

You do a fine job, you don't need to tell what you'r doing, you wast a lot of time on you video. Next you will do better.

[@joerogi8401]

I'm first woo hoo!

[@dalescribner3070]

Too much talking.