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Thread: Sandblasting and Compressor CFM question

  1. #1
    pumaking is offline New User
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    Default Sandblasting and Compressor CFM question

    Im quite curious as I am looking into purchasing a Abrasive Blasting kit and I noticed in some of the descriptions things such as consumes CFM and so psi.

    I'm also looking into purchasing a compressor but I want something small like a pancake one. MY concerns are does it matter if the Sandblaster kit states it consumes 6 CFM @ 90psi but the compressor states .6 CFM @ 90 PSI; 1.0 CFM @ 40 PSI


    Heres the sandblaster kit and compressor Im looking to purchase.



    3 GALLON, 100 PSI OILLESS AIR COMPRESSOR, Low maintenance oilless design, 120V, 2.6 amps; Air outlet: 1/4" - 18 NPT female; 6 ft. long 18 gauge power cord; Brass valve tank drain




    20 LB. PRESSURIZED ABRASIVE BLASTER




    I'm not looking for something big as my projects are relativly small.

  2. #2
    chromo is offline Experienced Metal Finisher
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    Default Re: Sandblasting and Compressor CFM question

    It makes a tremendous difference and that plain will not work! Maybe after an hour run time you could blast like 5 seconds if lucky!

    CFM means Cubic Feet per Minute. This is how much air is moved though the device like compressor or tools per minute. The higher the pressure used for the tool the faster the stored air moves out of the tank. The compressor has to replace that air in the tank again.

    You need the tank to store the air for various reasons, one is it gives the compressor time to rest and cool off when the tank gets full until you use enough air it needs to pump back up again. The bigger the tank the better and the compressor has to run less often. Also if your using air faster than the compressor pumps it, the tank fills and stores extra air while your doing other stuff, like switching parts or cleaning fresh blasted parts before doing the next parts. CFM more than the Blaster uses plus a large tank is best, CFM pretty close and a large tank will work, but you have to stop to let the compressor catch up and rest sometimes, CFM FAR below the CFM for the blaster will not work!

    The compressor unit, that does the work, should be rated near the CFM or more than the tools you'll use. If the compressor CFM is less than your tools then when working the compressor will never shut off because you use more air than it compresses which also means you'll run out of air and have to stop and wait for the compressor to fill up.
    My compressor is less CFM than my blaster uses and has a large tank 20 or 30 gallon? I blast a few minutes then the compressor starts running and I slowly run out of air and have to stop to let the compressor catch up. I'm not sure the CFM of my compressor, it's close enough to the CFM of the blaster that I can work awhile before I have to stop and often works out about the time I get a couple parts done and I have to stop to remove done parts and load others, so the compressor catches up and rests while I do other stuff than blasting.
    This is maybe a 4-5CFM@90PSI for a 6CFM@90psi use so it's not too bad but still a pain at times.
    I'm fixing my old LARGE compressor to use for blasting, this one is ok for now for the smaller stuff, won't be big enough when I do large stuff like axles and I would have to stop too often to let the compressor catch up and cool. I bought this compressor I use now before I was blasting to use for air tools like impact wrenches, air drills, ect that don't use high volumes of air for very long at a time.

    This is ok for some tools to have a compressor with less CFM than the tools if the tank is large. Stuff where your doing allot of other things and not just using the tool constant. Like an impact wrench, use it a few minutes to remove the lugnuts, then not using it while you change the tire, gives the compressor time to catch up before you put the nuts back on. So the stored air in the tank is running the impact gunicon, compressor catches up while you rotate your tires.
    On the other hand, an air sander, sandblaster, etc.. you use for a long time all at once, there is no chance for the compressor to catch up while your working.

    If the CFM of the compressor is more than the tools that is fine, it just means the compressor will fill up the tank faster and shut off till it needs to fill tank again, this is good.

    That compressor you showed is not good for much. Maybe use it for an Airbrush, perhaps an air nailer, air your car tires. Probably would be to slow for me to air my truck tires though! Certainly will not work for that sandblaster!

    If your projects are relatively small. you probably don't need a big blaster like that either.
    Of course you know blast media makes a big mess and is very bad to breath. You may want a blast cabinet of some type. You can buy one or build one, if you buy one it should come with a blast gun.
    Some of those PRESSURIZED ABRASIVE BLASTERs are not too good, kinda dangerous even for some people. A Syphon gun is cheap and may work well for small projects. I just bought a small $99 blast cabinet for small parts. Building my own large one but I needed something portable and needed it fast so I bought this one. Other than being too small for me it works very good. I been blasting wiper arms, lug wrenches, and such in it.
    It was about ready to use other than a light and shop vac for dust. Syphon feed sucks up the media stored in bottom of cabinet, media falls back to bottom for re-use so only need to load it once till you wear out the media. Use a good water seperator on the airline near the cabinet to keep media dry, so far no clogs for me and working well for small stuff.

  3. #3
    nuttyman's Avatar
    nuttyman is offline Metal Finishing Guru
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    Default Re: Sandblasting and Compressor CFM question

    the more cfm output the better. my comp. puts out 35cfm @ 175psi. powered by a 10 horse. the kit you have pictured will never work.
    SouthWest Powderworx
    Tyler Nutter
    5054803934
    www.swpowder.com
    myspace/swpowder
    tyler@swpowder.com

  4. #4
    pumaking is offline New User
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    Default Re: Sandblasting and Compressor CFM question

    Yea I kinda figured that the the extremly low CFM on that pancake would hinder the blasters performance, Glad I asked you guys before I went and bought that stuff.

    As much as I would love to get a big 10hp compressor the 2 main problems are Space and money. I only have a limited amount of space and I'd like to keep it under $140. So I'm taking your guys advice and reconsidering some options. Please tell me if this would be a better alternative.


    4 HP, 10 GALLON COMPRESSOR, 120V, 4HP (peak), 3HP (rated,) 3400 RPM, Air delivery: 4.5 SCFM @ 115 PSI; 5.6 SCFM @ 90PSI; 6.25 SCFM @ 70 PSI; 7.2 SCFM @ 40 PSI; Auto shutoff @ 115 PSI; Restart @ 85 PSI




    I cant get the specs on the syphon blasters but I assume they are like the blast cabinets that use syphon guns and state they operate at 5cfm.

    So would that compressor with the syphon unit be plenty? And to answer your question yes I will be building my own cabinet. I get the steel sheets cheap and can MIG weld it together. I dont mind if I have to wait a little to let the compressor catch up as I can do other stuff. Plus my main projects are pretty much Valve covers with the occasional 17" wheels.



    Oh and 1 more thing I greatly appreciate your responses and opinions guys. Im new to this sandblasting and powder coatingicon stuff and trying to get all my research done before I dump money on worthless stuff.

  5. #5
    nuttyman's Avatar
    nuttyman is offline Metal Finishing Guru
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    Default Re: Sandblasting and Compressor CFM question

    i've tried using that same syphon style gunicon with 1 of my smaller 25 gallon comps. & it still doesn't work that well, hardly @ all actually. until I purchased my big unit I took all my stuff to a blaster. my big comp. was over $2k so it's an investment for sure.
    SouthWest Powderworx
    Tyler Nutter
    5054803934
    www.swpowder.com
    myspace/swpowder
    tyler@swpowder.com

  6. #6
    pumaking is offline New User
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    Default Re: Sandblasting and Compressor CFM question

    Quote Originally Posted by nuttyman View Post
    i've tried using that same syphon style gunicon with 1 of my smaller 25 gallon comps. & it still doesn't work that well, hardly @ all actually. until I purchased my big unit I took all my stuff to a blaster. my big comp. was over $2k so it's an investment for sure.

    thanks nutty I guess I'll go with getting it done at a local blaster? How much did they usually charge you for something the size of a 4cyl valve cover.

    Also I have a bench grinder with a Wire Brush wheel that I usually use to remove paint and surface rust off my intercooler piping. Any down side to use a bench grinder with Wire Brush Wheel?

  7. #7
    baz
    baz is offline Metal Finishing Guru
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    Default Re: Sandblasting and Compressor CFM question

    another option would be if available in your area , some do it yourself place where you rent the place and tools to do mecanic work, sometimes they have a glassbead macine you can use for an hourly rate .

  8. #8
    jrow is offline Experienced Metal Finisher
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    Default Re: Sandblasting and Compressor CFM question

    pumaking,

    Check this site out. http://www.pablaster.com/

    John

  9. #9
    nuttyman's Avatar
    nuttyman is offline Metal Finishing Guru
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    Default Re: Sandblasting and Compressor CFM question

    the guy I use is very inexpensive. for instance I took a chopper frame, swing-arm, struts, fenders, kickstand & a few other accessories & was charged $25. I've taken lots of things to him over the years & his prices are very good.
    SouthWest Powderworx
    Tyler Nutter
    5054803934
    www.swpowder.com
    myspace/swpowder
    tyler@swpowder.com

  10. #10
    chromo is offline Experienced Metal Finisher
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    Default Re: Sandblasting and Compressor CFM question

    WOW Nuttyman, all that for $25? I'd say your getting a GREAT deal! Even $25 for the frame only is a great deal I would think! I don't know what any normal price is for blasting cause I never asked around here, but heck any shop wants $25 just to tell me why my brakes squeal and that don't count any repairs, which I do myself anyways and don't need them to tell me in the first place LOL
    I just like to see what they ask for checking them out, laugh, then leave.

    Pa blaster is worth checking out, I bought in for the $10, looked at the info sent to me but not logged onto site yet or forums. Been busy and not online much since the day I paid up, like last week. Might be a great idea for you to look at, so far I see I built a similar type unit almost for a steam cleaner years ago. I been building my own tools and such for nearly 20years or so though, so I'm pretty up on lots of things already before I even look at them.

    "Any down side to use a bench grinder with Wire Brush Wheel?"

    Kinda yes. Depending the brush and the cover, you could scratch the tar out of it perhaps.
    If a steal part you can strip the paint with strippers, make your own stripper from LYE for steel parts NOT ALUMINUM PARTS though.
    A tank or 2 and some DC currant you can remove rust also. Look into Electrolosys rust removal, not sure spelling.
    I've seen Simple Green, full strength from a gallon jug, remove some paints over time. Experimenting with that now myself.

    Nothing beats a good compressor. FORGET those stupid OILLESS AIR COMPRESSORs!!
    Get a real compressor, ignore the HYPE on that other JUNK!!
    Oilless and maintanance free simply means when it breaks toss it and buy a new one for full price again, no easy repairs, no cheap parts!! Also means CHEAP JUNK based on the ones I actually looked at myself at times! EVEN SEARS sells JUNK!
    I just noticed today on one of my CRAFTSMAN wrenches, the ugly 12MM rusted one, it says BF JAPAN!!! A JAPAN CRAFTSMAN WRENCH?? Must be one I found laying in the road sometime, I would NEVER buy a Japan wrench with a CRAFTSMAN name!!!

    Get a REAL compressor, a tank, a belt drive compressor head, real motor, etc...
    If you take good care of it it will last many many years! Change the oil sometimes, maybe adjust the belt, pretty much all there is and no big deal!
    Mine is abused!!! Sits outside in sun and rain and snow, never changed oil since day I bought it, never adjusted the belt, pretty much in several years never did anything to it at all! Runs perfect, like new, many hours of heavy use!
    I did lay it over once, I slipped and fell loading it in my truck and most the oil spilled out, so I put in fresh oil then because it was very low of course. Otherwise nothing!
    I think I paid around $300 for this one. A new compressor head if ever needed might cost $100? Motors are everywhere cheap if I ever need one, I have about 10 now I don't need just sitting here for other projects, cost $5-$15 each LOL!

    That looks like a cheap $20 or so blaster gunicon, it will probably work ok if the compressor has a decent CFM, and keep your media dry! Moisture in media will cause it to clog, will any blaster gun really. Use a good air water seperator/filter, not oiler. Try to keep your media line as short as you can from the gun to media tank/bucket. If you can mount a bucket or tank above the gun then you kinda get both a gravity feed and syphon feed both.

    If your building your own cabinet and using the syphon gun.
    Make the bottom sort of funnel shaped so the media runs down to a low spot as you blast, fill this funnel with media, place syphon hose in bottom of funnel. So when you blast the media is sucked from the funnel, more media slips downward, as you blast the media blown out falls back to funnel in bottom. Depending on size of cabinet, load about 10-20lbs of media and you can blast till media is plain worn out. Make a capped drain, a simple pipe and cap works, so you can open drain and let worn media run out to a bucket or such to empty, close drain and refill with new media.
    Make a decent hole to let fresh air into cabinet, make a baffle cover to keep media from blowing out. Put a shop vac hose on other end of cabinet, a baffle would be good also to prevent sucking much flying media out of the cabinet, this sucks out the dust.
    Install a good light of some type so you can see well, preferably where media is not blown into it directly!
    Use tempered glass or plexy for window, cover inside of window with clear plastic, kitchen wrap should work well, this helps window avoid scratches. I have a heavy clear plastic I use allot that was factory scraps from out door table clothes of some type. Use it for green house, solar heat, and many other things.
    Remember of course, blasting removes paint right! So if your media will be hitting the back of the cabinet inside, like a small cabinet will, you may want the plastic wrap or such on the back wall also. This will prevent you from blasting the nice pretty paint right off your cabinet right away.
    Make sure you have good seals on all cabinet doors and a good vacume suction going, this will keep dust out of shop and in the shop vac where it belongs. Make sure your shop vac filter is secure! My new shop vac the cheap junk ring keeps falling off! I have it pressed on secure and tight and everything is fine for awhile, then I see dust blowing out the vac exhaust! I stop working and open the vac, and ring is laying in tank with filter loose! Lucky I am working outdoors!!!
    Wal-mart is getting this junky shop-vac back my next trip to town!! Other than the filter comming loose all the time it was a good vac with good suction.

    If you build the PA Blaster type unit the gun will probably work better than as plain syphon feed. You should be able to build a PA Blaster cheaper than buying a pressure pot like you first showed you were thinking about. A PA Blaster should also be far safer than any pressure pot.

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