Media Blasting

Discussion in 'Gunsmithing' started by Forester, Jan 5, 2011.

  1. Forester

    Forester Well-Known Member

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    I am thinking about getting into doing a little bit of refinishing work on my own guns...just something new to tinker with really.

    What material and grit is a good choice for these applications?


    • Preparation before spraying Duracoat- I see 120grit Aluminum oxide recommended?


    • Just knocking the shine off of a brushed stainless finish?


    How difficult is it to get a nice even looking finish if the blasted stainless is to be the final finish?

    How do you protect the muzzle crown when blasting?


    What else should I know and probably don't? Pictures of different finishes would be great too if possible!
     
    Last edited: Jan 5, 2011
  2. J E Custom

    J E Custom Well-Known Member

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    I like to use sugar sand (very fine) because it is not very aggressive and makes it easy to make
    the finish very uniform.

    To protect the muzzle I use a ear plug in the bore and direct the blast away from the crown,
    and tape the tenon and chamber to prevent any sand from entering.

    I also totally blast the action before assembly using a turned wooden dowel that fits in the
    receiver snug to protect the internal surfaces, and throughly clean before assembly.

    The sugar sand does a nice job that is non-reflective.

    I hope this helps.

    J E CUSTOM
     

  3. Forester

    Forester Well-Known Member

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    Is that like the "play sand" at Lowes? If so that certainly has the benefit of being cheap and easy to find locally.

    Another question. I'm not going into business doing this so I don't need the biggest and best equipment, but I hate to buy junk too. There are several setups available at Harbor Freight and Northern Hydraulic but they all seem to need a pretty big compressor to operate.

    I have a 5HP 17gallon tank compressor rated at 6.5CFM @ 40PSI and 5.1CFM at 90PSI 150PSI Max

    Are there any decent media blast setups out there for gun work and other light utility type work for ~$150.00 or so?

    The one I was considering is here: Portable Abrasive Blaster Kit

    Air consumption seems to easily fit my compressor, and it is certainly cheap enough.
     
  4. shortgrass

    shortgrass Well-Known Member

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    "Play sand" and media used for finishing are two different things. Media used for finishing is glass beads, sometimes aluminum oxide. Most blast cabinets, that are worth while, require a pretty fair amount of air volume.
     
  5. Forester

    Forester Well-Known Member

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    I understand what glass beads and aluminum oxide are. What I was trying to understand is exactly what JE Custom way referring too as "Sugar Sand"

    I am not looking for a cabinet, I don't want to take up the shop space. I am fine with losing the blasting material so a small portable unit is more in line with what I am looking for.
     
  6. Forester

    Forester Well-Known Member

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    What media was used on the barrel for the rifle on your home page?
     
  7. shortgrass

    shortgrass Well-Known Member

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    80-100 mesh glass beads.
     
  8. J E Custom

    J E Custom Well-Known Member

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    Sugar Sand is very fine Silica Sand and runs about $8.00 a 100 lb bag. It is white and will work in small portable blasters.

    It puts a fine mat finish on stainless and should only be used once(Don't try to save the used sand)
    because it may discolor the finish and will not be uniform.

    Sometimes I use a small hand held blaster that resembles a paint gun for small jobs (It has it's
    sand hopper on the blast head).

    Glass beads and other blasting media work well in larger blasting cabinet's that recycle the media
    because of expense. But if blasting/removing paint or other finishes it will become contaminated
    and needs to be replaced periodically.

    J E CUSTOM
     
  9. specweldtom

    specweldtom Well-Known Member

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    Forester, I believe that sugar sand is also called #5 blasting sand. I used it in my small cabinet and also in a total-loss outdoor pot and a couple of the 1 quart hand held guns. It breaks up in a cabinet and creates a lot of dust, so I switched to 70 grit aluminum oxide media from Harbor Freight. Works good, and doesn't fracture and create a lot of dust. If you are careful about not putting painted, excessively rusty, or oily parts in the cabinet, it'll last a long time. I've been using about 50 lbs of it for over a year. I also use glass beads and walnut hulls in the hand-helds for aluminum parts and for a prettier satin finish than the media or the sugar sand. I have a 15 cfm 60 gal. compressor, and it can't maintain but about 90 psi in my cabinet gun or the pressure pot. Tank size doesn't help if you blast more than about 2-3 minutes. After that it's up to the compressor to keep up. I paid $1000 for an Ingersoll-Rand 2 stage compressor, and if I could have a do-over, I'd cough up the extra $400 for the 24 cfm version. The 5 hp motor fried itself after 3 years, and I replaced it with a 7 1/2 hp motor (same frame). That motor cost me about what the difference was for the bigger compressor. I have never regretted the decision to bite the bullet and get a heavy duty compressor though. Other than the first motor, this one takes a licking and keeps on ticking. I can live with it.

    You're on the right track getting set up to blast. No matter what setup you end up with, you'll use it for all kinds of stuff.
     
  10. Forester

    Forester Well-Known Member

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    Thanks for the detailed info. I would love to buy a big compressor, but with a very large tax bill looming it is not in the cards. I am willing to live with blasting slowly and waiting on my smaller compressor as long as the finished product is good.

    I picked up a small portable blaster and gave it a try this week...initial results were promising. The duracoat will be here next week. I think I am going to put a nice finish on an ammo can for practice before I go anywhere near the gun cabinet.:D
     
  11. specweldtom

    specweldtom Well-Known Member

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    I forgot to mention that I have moisture knockout pots everywhere in the system. One right off the compressor, another where the lines branch out, a third one on the air inlet to the cabinet, and one on every portable pot or gun. The climate where I live is usually humid, and if you don't knock the condensate out of the air, it will entrain and slobber on the piece you're trying to prep. Nothing good comes of oily, wet air getting into your media, or on a workpiece. If I blast for 2 -3 hours, the compressor runs almost all that time, and I will drain about a cupfull of water (with a little oil sheen) out of the knockouts. In that same time frame, I'll blow a quart or more out of the tank drain, so it's catching most of it, but not enough.

    I also burn a 25 -40 watt light bulb 24/7 in my cabinet to keep the media dry. Works.

    Tom
     
    Last edited: Jan 8, 2011
  12. julietvictor

    julietvictor Active Member

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    I use Aluminum Oxide for surface prep before duracoating. Works great, nice rough uniform finish, duracoat adheres well. I usually use glass media for stainless steel parts. It creates a nice semi-matte sheen. Very uniform. I have been lazy once or twice a did a quick blast job with glass beads then followed woth a duracoat finish. Does NOT adhere well at all. If your media gets dirty or stops cutting, replace it. It is a whole lot easier to replace it when it gets "worn out" than standing there hunched over for twice as long trying to do the same job.

    One time I forgot to plug the muzzle end of a Stainless varmint barrel before glass bead blasting. Big mistake. Had to have the Muzzle cut down and recrowned. The "gunsmith" (what do you call an incompetent gunsmith?) that did the crown- I wanted an 11 degree target crown- cut the crown at, around 30 degrees with a 45-60 degree chamfer. None of it was concentric- not even close. Had him redo it, same thing. I had to buy a PTG 11 degree crown tool, came out perfect, but wasn't cheap. It now shoots again, actually better than before. Lesson learned- plug the muzzle and chamber, protect your threads.
     
  13. specweldtom

    specweldtom Well-Known Member

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    julietvictor, I used to plug bores with the silicon rubber tapered plugs from Brownell's, and just blast down along the barrel without ever aiming across or back toward the muzzle. Recently, I started doing what JE does, using foam ear plugs shoved into the muzzle, but I trim them flush and stick a piece of duct tape on the face and trim it to the O.D. of the muzzle. It is real sticky and won't come off. I still don't aim across or at the crown though. Crowns come out as bright as when they were turned.

    Tom
     
  14. julietvictor

    julietvictor Active Member

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    specweldtom, I learned the hard way on that one. I do the same to the crowns now as well, for the most part. I have a large supply of the silicone earplugs and they work great. I never feel good about blasting the crown, the only times I have done it were on the stainless steel barrel, previously mentioned, which now has a beautifully turned crown with a glass beaded barrel and for Duracoat jobs. I found with the Duracoat, in the past, if I don't blast the crown I have problems with the Duracoat chipping at the crown. Attributed to prep?, probably, maybe other factors, but I just hit it enough to get a light texture for the Duracoat to grab.

    I have also used clay, the stuff I use when bedding, for plugging the barrel. Obviously it is sticky and attracts the media. Kind of works, kind of doesn't. But, definitely plugging, masking and not blasting is THE best, unless you are looking for a specific finish.