sandblasting question

[Guest Vuk]

Hello,

 

I would like to know what you guys think.

Will this compressor pump with 5.5HP motor and 71 Gallon tank be ok for sandblasting?

https://www.rolair.com/products/pumps/belt-drive-two-stage/pmp22k28ch

 

I know I have to use smaller nozzles.

 

I'm not going to use it as a professional. More like a hobby, sandblasting car wheels now and then.

 

[kgreen]

Yes, it will work.  It will obviously be slower than the mamouth blasters you see in commercial shops but should serve your needs well.  I have one of similar size, it is quicker and more effective than the wire wheel.  My work is limited to small parts in a blast cabinet though I can change it around and use it outside of the cabinet.

 

Don't forget your respiratory safety!  exhaust blast cabinet outside, when using without blast cabinet use a full face respirator.

[Joe in Canada]

It will depend on the size of the nozzle you will be using with the CFM the pump will put out and at what PSI your work pressure is set at. The larger the nozzle the more air it will use and the faster it will clean the work piece.

[jpage]

People are fooled by the motor size on air compressors.  5 hp sounds impressive when you could actually get more CFM from a 2 hp motor with the right compressor. When buying a compressor, you should always look for the CFM ratings at 90 PSI. Most air tools run at 90 PSI but you may want to sandblast at a higher pressure. Best if you can find a compressor that will give you at least 15 CFM at 90 PSI but I have sandblasted with small units but it takes forever and you won't get the best results. My suggestion, if you are going to do a whole car, is to take it to an experienced sandblaster. You'll get a better job done, especially on the chassis and running gear,and it might cost you just a bit more than a good compressor. You might also look into chemical stripping which is very effective on rust and paint, somewhat easier on the metal and costs about the same.

[Restorer32]

Yes you can sandblast with that compressor but you will find it incredibly frustrating. Anything other than a tiny nozzle will quickly drain your compressor tank. 

[Guest Vuk]

Compressor spec.

The tank is listed at 10 bars (145 PSI).

Siphon gun is listed at max 8 bars (116 PSI)

Tank size 71 Gallon

 

Pump:

CFM DISPLACED     20.35

CFM DELIVERED     15.87 @ 175 PSI

 

 

 

[Amphicar BUYER]

If you use a small nozzle and take your time, you may OK for a while. Be sure that you allow your compressor to cool (add a fan maybe). Blasters use a LOT of volume so be aware of the run time. The spec you need is the CFM or volume of air it can supply constantly not so much it's capacity. You will find it can deliver for a short time, but will soon be running constantly trying to keep up as your pressure drops. 

[Restorer32]

Back when we did 48 + hours sandblasting a week we would tell folks who asked about price that sandblasting is similar to painting. With our 175cfm diesel compressor and a 5/16 nozzle blasting was like painting with a 2" brush and took about the same amount of time. You will be painting with a 1/4" brush. You can do what you want to do with it but it will be slow. You can use relatively coarse blasting sand on wheels so that will help a bit. 

[Guest Vuk]

I just bought this thing and I have 0 experiance with air tools.

So when I'm blasting I'm blasting till compressor kicks in. Then I wait for the pump to fill up the tank and then I can continue blasting. Or should I continue blasting with the pump working (if pressure in the nozzle isn't changing). So the pump is filling the compressor with air faster than I can spend it.

I read somewhere I should wait after the pump fills the tank to let it cool about the same time it spent filling it.

 

[Rusty_OToole]

Most tire stores offer a service to bead blast and paint your wheels. I found the price very reasonable, even if the color selection was not great. But, I would rather have them do it and repaint when I got them home than do them myself. Sandblasting wheels is nasty. They only charged $20 a wheel but this was 15 years ago.

[Guest Vuk]

I'm more DIY type of guy. I like doing stuff. I just hope my compressor can handle it. I'm thinking of building a sandblasting cabin large enough to put a wheel in it.

[jpage]

I used to sandblast on a large tarp so that I could retain much of the sand. I used to buy silica sand at a local cement works for about 5 bucks a bag. Now some of that stuff is really expensive. Also, some monument companies will do small sandblast jobs but I wouldn't trust them with anything but wheels and frame parts. Our local industrial sandblast company will do it for $75 an hour. They can do a whole chassis and running gear in about 2 hrs.

Edited November 3, 2016 by jpage (see edit history)

[Amphicar BUYER]

I have yet to see any tire shop offer blast/paint services.

 

Keep an eye on your pressure, as it drops so will the effectiveness of the blast. I don't think your machine can keep up with constant blasting. Get a fan on the motor and compressor to help keep it as cool as possible. Take your time, do some once your pressure drops go have lunch while it builds and cools some. You may only get a few mins at a time. Wheels can be a pain depending on the paint and the media you are using.

[leon bee]

One thing I've gotten real fond of is my Speed Blaster. I think it's Zendex brand. Been using it on anything won't fit in my bead cabinet, using that coal slag stuff Tractor supply sells.........fine grit. Even with a decent compressor it's slow, but hey: it works!

[Amphicar BUYER]

I have one of those Speed Blasters, great for small spot blasting too. I also have a blaster with a vacuum brush head that recirculates the media. Love that mo-chine!

[Rusty_OToole]

1 hour ago, Amphicar BUYER said:

I have yet to see any tire shop offer blast/paint services.

 Northumberland Tire in Port Hope, Ontario, Canada did mine. I am sure there are others, some much closer to you. It is actually more popular for big truck wheels but they can do car wheels too. Try a local tire place that does a lot of  truck tires.

Edited November 3, 2016 by Rusty_OToole (see edit history)

[MochetVelo]

"...when I'm blasting I'm blasting till compressor kicks in. Then I wait for the pump to fill up the tank and then I can continue blasting. Or should I continue blasting with the pump working?"

 

 

I use a fairly small compressor, so it recycles frequently. I just keep blasting as the compressor runs and it works OK. 

 

Phil

[capngrog]

Although this thread has included several comments on what will not work for sandblasting, I haven't seen any comments on what is recommended for hobby use sandblasting.  How about some recommendations on cfm, tank volume, pressure and nozzle size for openers.  I know next to nothing about sand/media blasting and would appreciate some recommendations for a good hobby (not frequent service commercial use) sand blasting set up.

 

I need all the help I can get,

Grog

[Digger914]

3 hours ago, capngrog said:

Although this thread has included several comments on what will not work for sandblasting, I haven't seen any comments on what is recommended for hobby use sandblasting.  How about some recommendations on cfm, tank volume, pressure and nozzle size for openers.  I know next to nothing about sand/media blasting and would appreciate some recommendations for a good hobby (not frequent service commercial use) sand blasting set up.

 

I need all the help I can get,

Grog

 

I have a couple of different sandblasting setups and I have found that even a small compressor will eventually fill a large pressure tank and the more air available the longer you can work before you have to stop and wait.

 

The cheapest medium for sand blasting is good old sand, get some bags of play sand from the home store. Sand likes to absorb moisture and it takes a lot of air to move damp sand, so spread it thin on a tarp to dry in the sun then dump it in your hopper and have at it.

 

Syphon sand blasters suck, literally and figuratively. I have one for small jobs, a gravity feed for larger jobs and if I was serious about getting the job done as fast as possible I would have a pressurized gravity feed.

 

Different medium for different things, I live in rust country and I'm tooled up for rust. For least abrasive cleaning ground up peanut shells, for cleaning out small rust pits silica sand, smallest nozzle that will fit your gun and lowest pressure that will work. Not because that's the best way, just helps control the size of the mess to clean up after.

 

Small hikers instant set up camping tents are cheap and make excellent portable blast enclosures, they don't take up much space when not in use and depending on your blast medium you can get more than one use out of them.

 

Dressing for a car frame takes more than a blasting hood and thick leather gloves, whatever hits that solid steel straight on is coming right back at you, along with the powder fine sharp fragments of rust it knocked loose. 

 

Bigger jobs take more air than the average 120 psi 30 gal home compressor, three of those hooked to the same airline will keep up with any sand blaster you can buy at the home store. If your brother doesn't have a compressor you can use, buy him one for Christmas and borrow it from him when you need it.

 

Except for the abrasive factor requiring a more robust garment, personal safety with sand blasting isn't a whole lot different than spray painting. Protect your eyes, protect your lungs, protect your skin.

 

 

 

 

 

 

[capngrog]

Thanks, Digger.  That information is very helpful.

 

Cheers,

Grog

[39BuickEight]

We used the cheap Harbor Freight 5 gallon sand blaster, a big upright compressor, and Black Beauty (reused it 3-4 times, pour it back in, no need to buy more).  Worked great.  We have blasted the frame, body, fenders, suspension, etc.  Anything on the car that wouldn't fit in out blasting cabinet.   If you click on my build thread in my signature you will see we also made a temporary blasting "room" in the shop so we could work when the weather did not cooperate.

 

https://images-na.ssl-images-amazon.com/images/I/31a6739XESL.jpg

 

 

Edited November 4, 2016 by 39BuickEight (see edit history)

[stakeside]

1 hour ago, 39BuickEight said:

We used the cheap Harbor Freight 5 gallon sand blaster, a big upright compressor, and Black Beauty (reused it 3-4 times, pour it back in, no need to buy more).  Worked great.  We have blasted the frame, body, fenders, suspension, etc.  Anything on the car that wouldn't fit in out blasting cabinet.   If you click on my build thread in my signature you will see we also made a temporary blasting "room" in the shop so we could work when the weather did not cooperate.

 

https://images-na.ssl-images-amazon.com/images/I/31a6739XESL.jpg

 

 

This worked good for me. Used this system on my rims for my Dodge Bros truck. Only regret should have got larger tank. Small tank empties fast.

Edited November 4, 2016 by stakeside
Error (see edit history)

[Guest Vuk]

Awsome info guys, thanks alot.

 

39BuickEight, what is the CFM of that 60 gallon compressor?

 

So I've been looking at these two pumps.

They are almost the same. Both are K28 but from different manufacturers. One is from Rolair and other is Chinook.

Rolair is listed at 20.35 CFM (link is in the #1 post)

Chinook is listed at 23.4 CFM (http://www.fps-compressors.co.uk/k28_belt-driven_pump.html)

So what is the difference?

I was doing some reasearch and I think they share the same flywheel size and cylinder size.

Will I increase CFM to Rolair pump if I put stronger and a bit faster motor?

[39BuickEight]

I think it's around 10.  Just a single stage 60gal $500 compressor.  Nothing fancy.  We don't run it more than 30 minutes without letting it cool down-it keeps up fine, but it just seems like a good idea.  You can do a lot of blasting in 30 min though when you're just a DIYer.

[DavidAU]

One thing you should have when using a sandblaster (and a spray gun) with a compressor of any size is a good water trap just before the compressed air enters the sandblaster.  

When the air is compressed it heats up and the condensation in the air turns to water and will block the sand as it comes out of the sandblasting gun.  It can be most frustrating.

[Guest Vuk]

yeah

I saw people doing copper pipe water trap. Might be a good idea.

[R Walling]

 Quote,

 

 " So when I'm blasting I'm blasting till compressor kicks in. Then I wait for the pump to fill up the tank and then I can continue blasting"

 

 If you wait for the compressor to build up pressure, start sandblasting just before the compressor shuts off as it cost more to start the compressor than to keep it running.

 Just buy a small fan to keep it cool. (sandblasting below 80 lbs pressure is a waste of time and sand)

 

I feel that if you are having a problem with the sand clumping up in a pressure blaster from condensed water, it is better to use a siphon blaster connected to an overhead bucket with a fairly short 1/2' hose.The sand will flow down and the siphon will suck it into the gun.

 

 I find that using sand over takes twice as long and creates four times the dust.

(not to mention the clogs from large rust flakes)

[Guest Grumpy's Auto Shop]

Oh, boy.  Lots I can say on this and most of it I won't (because I didn't expect the pop-quiz...)

 

First off --not to be anal about this, but the needed figure is sCFM.  The consumption in sCFM needs to match the supply in sCFM, else the results may be frustrating.  The long and short of it is that you can run a half-inch Impact for a LOT longer than a die grinder.

 

The most significant area one will see this is when painting, but un-painting is a close second.

 

With that out of the way, I can say with the authority of years of painful research that an under-rated compressor CAN work by increasing the reserve available on-demand.  Buy cheap, large tanks on craigslist and plumb them together, then you can run longer before the compressor kicks on.  The only liability other than the real estate needed is that you have more 'break time' while the system recharges.  This slows the process and may get progressively worse, depending on how you spend your breaks,

 

This might be a good time though to bring up another aspect.

For years I have used and tested various products, each of which promised to make me forget I ever sliced my own bread and in most cases I wanted my $5 back, then resumed what I had been doing before.  One example would be using White Lithium on various parts of the car, such as hinges.  Recently however I disabused myself of this and now favor 'dry-lube', which is powdered teflon carried in a high-flash solvent.  It works great and is WAY less messy.  I also use 3 different types/brands of 'silly-spray', each for a different purpose.

 

I won't get into any product endorsements, partly because if I tell you, then I'll have to kill you, and I like you guys...  The point however is that there is a paradigm shift and some modern products are far superior to the old school stuff.

 

Same goes for media-blasting.  There are new methods and techniques, the results of which often blow all the crap off the way we have been doing it.  Maybe it's just me but I never liked sandblasting largely because of the mess.  My wife didn't like the laundry ramifications either.

 

I have played a but with electrolytic and it's pretty amazing what a 1952 'Boat Tender' can do, but it's difficult to set up for large parts. (a member here recently posted his write-up on the subject, which I still need to check out).

 

I have also tried 'soda' using both my top-loader and my siphon-feed with regular old Arm and Hammer from the grocery and it is equally impressive.  Definitely seems to want a small nozzle though. Since the media is so fine it can easily disappear before it does any good.

 

Next on my list to test is Dry Ice.

 

At then end of the day though I think that 'one size fits all' remains one of the three fundamental lies.  Each job has its own technique that will yield the best results and one should choose accordingly.  This is particularly true of antique cars and replacement parts that are made of unobtanium.  My bylaw is always start with the most benign method:  A bigger hammer begets bigger regrets.

One last thought: When it comes to wholesale paint stripping, chemical is the way to go. Do not pass Go, do not collect $200. (and do not ask me how I know this...)

 

 

 

 

 

[Guest Vuk]

I have a chance to get B5900B or K28

 

which pump is better.

 

this is what I found about both.

 

B5900B spins at higher rpm's so it gets hot quicker then k28

 

K28 has more intercoolers/aftercoolers

 

 

B5900B
Bore - Large Piston - 4.125"
Bore - Small Piston - 2.162"
Stroke - 2.190

K28

BORE LOW PRESSURE 3.74"

BORE HIGH PRESSURE 1.97"

STROKE 2.56"

 

K28 pump is heavier.

 

B5900B has 23.2 CFM DISPLACED

K28 has 20.35CFMDISPLACED

 

B5900B I found it has 17.7cfm delivered

K28 has 17 cfm @ 100 PSI, although I found on ebay listed as 18.11cfm delivered

 

whats your opinion? which one will deliver more cfm.

 

I personally think K28 is built better, although B5900B pump is also a good quality pump.

 

Or am I just overthinking too much because I wanna get better one but both are the same...

 

K28

 

B5900B

 

Edited November 11, 2016 by Vuk (see edit history)

[Friartuck]

Comments mentioned and not mentioned:

• Water separator just before blaster
• Force dry (heat) blasting media before pouring into hopper. I dry media in a stainless kitchen pan on the BBQ grill.
• Blast on tarp and can recover 90 percent of the blast media
• Use a strainer (screen) at all times (even media from the new bag may have debris). Nothing more frustrating that clearing a clog.
• Good canvas hood. Have a few glass window inserts to replace them quickly. You can cover the glass inserts with clear packing tape and replace tape.
• Good air respirator. A fresh air supply system is best if available.
• You can blast at pressures as little as 40 pounds to minimize/prevent panel warping. Blasting at lower pressures also eases air CFM. 

[kgreen]

This is a cool option (pun intended) for sandblasting autobody parts.  https://www.dustlessblasting.com/products.html

 

I can get a car blasted in half a day for about $1,800.  I'll have removed the glass, trim, chrome, etc and have body panels removed from the car to get the undersides of the fenders and greater access to the frame.  After the blast is complete there is a rinse that will hold flash rust for about 3 days.  The epoxy primer can be applied directly over the rinsed but dry surface.  The water keeps the temps down so the panels do not warp.  The blasting does not work well on soft materials like seam sealer and undercoating.  It does a thorough job removing rust.  I find these guys on Craigslist, then they come to your house.  The clean up in your driveway is EZ.

[Restorer32]

Once again, the warping problem when sandblasting has nothing to do with heat. It is the peening effect of the sand grains hitting the surface of the metal that  potentially  can cause warping. You can warp metal blasting it with dry ice same as with sand.

 

[kgreen]

1 hour ago, Restorer32 said:

Once again, the warping problem when sandblasting has nothing to do with heat. It is the peening effect of the sand grains hitting the surface of the metal that  potentially  can cause warping. You can warp metal blasting it with dry ice same as with sand.

 

As the heat from dry sand blasting expands the metal, the super cold from the dry ice blasting can contract the metal.  In both cases it is the significant temperature change on a portion of the panel relative to the unblasted portions of the panel that causes the panel to warp.

[Restorer32]

Good theory but not true. It is the peening effect just as hammering a piece of metal on one side causes it to warp. There is not nearly enough temperature change to cause heat distortion. Study the coefficient of expansion as related to heat rise and you will see that the rise in temp, if there is in fact any detectable, is nowhere near enough to cause warping.

[kgreen]

2 hours ago, Restorer32 said:

Good theory but not true. It is the peening effect just as hammering a piece of metal on one side causes it to warp. There is not nearly enough temperature change to cause heat distortion. Study the coefficient of expansion as related to heat rise and you will see that the rise in temp, if there is in fact any detectable, is nowhere near enough to cause warping.

Further research on my part substantiates your point above.  I appreciate your patience and clarity.

Old myth dispelled.  But how does the water blast method not warp metal? 

Edited November 11, 2016 by sixseven (see edit history)

[Restorer32]

I didn't mean to come off as a smart a**. We sandblasted 30+ hrs/wk for maybe 20 years, everything from dump truck beds to Stearman biplane air frames.to Duesenberg body panels. Sandblasting as a low angle to the metal is the best way to minimize the danger of warping but it is virtually impossible to blast a perfectly flat piece without warpage, just as you can't hammer a flat piece without warping it. I once pretty much destroyed an antique steel toy by blasting too aggressively in our glass bead cabinet. The lower the air pressure the lesser the chance of warpage just like heavy blows with a hammer are more damaging that softer blows. We are currently doing a frame up show restoration of a 1960 Cadillac Biarritz, very rusty. We blasted the body minus the doors, hood, fenders and trunk. Those we will chemically and mechanically strip then blast the formed edges only.

[kgreen]

2 hours ago, Restorer32 said:

I didn't mean to come off as a smart a**. 

We're good.  I can't believe all of my notions and stand ready to confirm myself.

[Guest Vuk]

I have 3/8" coupler on air compressor. Will 3/8" air hose feeding the pressurized blaster be enough?

Or should I upgrade to 1/2" that means changing the regulator water filter and hose?

Edited November 24, 2016 by Vuk (see edit history)

[Friartuck]

The 3/8 maybe enough, depending on the CFM contemplated. I personally use 1/2 inch coupler and 1/2 inch air hose for blasting even though I typically blast at low pressure, low CFM. I use 3/8 for all other types of shop equipment. Being as you've set up with 3/8 already, try 3/8 at low pressure and see your results. If the air pressure at the hopper drops after continuous use, you'll know the 3/8 is restricting the air. I suspect 3/8 running at 35-40 pounds will be enough.

[Guest Grumpy's Auto Shop]

On 11/24/2016 at 11:38 AM, Vuk said:

I have 3/8" coupler on air compressor. Will 3/8" air hose feeding the pressurized blaster be enough?

Or should I upgrade to 1/2" that means changing the regulator water filter and hose?

 

You should be fine with 3/8".  And, as a general rule, ALL your air tools will perform better and last longer on pressure that is LESS than the compressor's max (ie. 90psi with a 120max).  That is, unless you're trying to blow holes through something.