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Media Blasting

 
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  #15  
Old 01-12-2011, 08:54 AM
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Re: Media Blasting

I haven't done any duracoating yet. When I do, I'll know how to prep for it. It obviously needs the anchor pattern to really adhere. The 70 grit Al Ox sounds like it's the way to go.

Thanks, Tom
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  #16  
Old 01-12-2011, 02:00 PM
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Re: Media Blasting

Quote:
Originally Posted by julietvictor View Post
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.
Do you have a pic of the bead blast finish you mentioned? I have 2 rifles I want to coat and one that I want something akin to a french grey on.
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  #17  
Old 01-12-2011, 03:04 PM
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Re: Media Blasting

I think you can mimic the French gray (darker matte gray, if I am correct?) by using aluminum oxide instead of bead blasting. But depending on the alloy it may make it more susceptible to rusting. I have had a couple Lothar Walthers and an ER shaw Stainless barrel(s) rust. Mind you, they were left in a HIGH humidity environment unprotected (we have evaportive (swamp) coolers instead of air conditioning) where I live. I can try to get a pic but it may be a little bit.
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  #18  
Old 01-17-2011, 12:54 PM
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Re: Media Blasting

Well I bit the bullet Saturday and after practicing on some scrap material I blasted my 7-300WSM with 120grit aluminum oxide. and then duracoated it.

Blasting went well, and I was able to get a very nice, consistent finish across the various parts. I did have to work very, very slow so that my air compressor could keep up. I did hit the internal temp shutoff on it once while blasting leading to an hour wait to start again. A bigger compressor is on the shopping list now, just need to liberate some funds from other priorities sometime.

For the duracoat part, I could not be more pleased. I rigged up a paint cabinet of sorts in my shop with a tarp and box fan. It worked well and kept the dust out and mess in.

I degreased with trustrip, blasted with Al. Oxide, and painted with an HVLP spray gun from Harbor Freight. The spray gun has a 1.0mm nozzle which is on the large end of what Lauer recommends but with the material adjustment knob turned down I had no problem avoiding runs and the over-spray was very minimal. I coated with combat black and then used the duraclear over top.

All in all things turned out as good or better than I hoped for. The parts are now in my safe curing as I will not need this rifle for awhile so I will let it set up for a week or two before I fool with it much. Actually I am waiting on a Manners stock that wont be here until March so the gun wont get any use until then.
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  #19  
Old 01-18-2011, 01:40 AM
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Re: Media Blasting

Once you have used your aluminum oxide on regular steel it will be contaminated and blow steel bits into your stainless and cause it to rust. If I have a steel receiver and a stainless barrel I will do them with the same media but do the stainless first and the steel parts last. Then that media gets pulled and saved for steel jobs. I run as little media as possible in the cabinet. Usually 4-5 pounds will feed it nicely.

The proper surface for most coatings is very specific 100-120 grit aluminum oxide. Too rough and it will scratch the coating off of the peaks. To fine and it will chip easily. I use rubber bottle stoppers to protect muzzles and chambers. They bulge over the edge slightly and protect the crown nicely even when directing the media directly at it. I never have trouble with chipping near a crown.
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Last edited by Hired Gun; 01-20-2011 at 11:33 PM.
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  #20  
Old 01-20-2011, 08:52 AM
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Re: Media Blasting

Quote:
Originally Posted by Hired Gun View Post
Once you have used your aluminum oxide on regular steel it will be contaminated and blow steel bits into your stainless and cause it to rust. If I have a steel receiver and a stainless barrel I will do them with the same media but do the stainless first and the steel parts last. Then that media get pulled and saved for steel jobs. I run as little amount of media as possible in the cabinet. Usually 4-5 pounds will feed it nicely.

The proper surface for most coatings is very specific 100-120 grit aluminum oxide. Too rough and it will scratch the coating off of the peaks. To fine and it will chip easily. I use rubber bottle stoppers to protect muzzles and chambers. They bulge over the edge slightly and protect the crown nicely even when directing the media directly at it. I never have trouble with chipping near a crown.

My blast cabinet was a cardboard box...so not much risk of me re-using blasting media. But good to know nonetheless.

SWMBO blessed a new air compressor without a blink so i will get that setup before I tackle the 3 other rifles I want to blast and or Duracoat.
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  #21  
Old 01-20-2011, 08:28 PM
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Re: Media Blasting

Have you found the compressor you want? My only recommendation is to stay away from the high rpm (direct drive) oil-less compressors. Some have rated outputs of 10 cfm or more, but I've never seen one hold together in hard use. They also have maximum pressures of around 125 psig. Fine for air tools, but my cabinet blaster likes 135-150 psig, and that pressure doesn't hurt any of the siphon blast guns. Might be too high for pressure pots though.

Good luck. Tom
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