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Posted: 7/26/2016 10:10:45 PM EDT
[#1]
Aluminum oxide. 90 grit or higher.
75 will work in a pinch. |
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Posted: 7/27/2016 10:00:10 PM EDT
[#2]
OK I'll give that a try.
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Posted: 7/30/2016 8:24:33 AM EDT
[#3]
You can use some emery cloth to knock down the the big burrs/scartches, then finish it off with bead blasting.
I use 120 grit aluminum oxide @ 45 PSI. |
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Posted: 8/12/2016 12:02:37 AM EDT
[#4]
I blast with AlO 120gr as well. I get closer to the material for more aggressive removal of machine marks. 45psi sounds about right. I've gone up to 60psi and move the gun back.
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Posted: 8/22/2016 11:51:24 AM EDT
[#5]
I've got some 120 grit coming in this week and I'm going to give it a try.
How careful do I need to be around pin holes, threads, etc... ? |
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Posted: 8/24/2016 11:51:41 PM EDT
[#6]
I've never been extra careful around holes or threads but it makes sense not to linger there too long or too close blasting.
I've had to blast Gunkote off 3 lowers and pushed the pressure up to 80lbs to get it done and the pins were still snug afterwards. The rear threads for the buffer tube were blasted to make sure the Gunkote had something to stick to. No problems there. If your coating with something afterwards, you might have a tight pin fit anyways. |
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Posted: 8/26/2016 9:29:08 AM EDT
[#7]
I can't imagine how long, and hard you would have to blast a lower with 120 AO to egg pin holes. Honestly, I don't think it's possible without actively trying to achieve that result.
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Posted: 8/31/2016 6:50:23 PM EDT
[#8]
I blasted a raw forged lower today for practice and then did my billet one. I used 120 grit AO at 45 psi.
I am very happy with the results. Thank you for all of your advice. Before and after pics:    |
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Posted: 9/5/2016 4:22:00 AM EDT
[#9]
That came out with a nice and smooth finish. Are you anodizing before coating or straight to coating?
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Posted: 9/5/2016 7:26:58 AM EDT
[#10]
I was taught, many years ago, that sand blasting will actually make the part "bigger." i.e. Your pin hole clearance would get smaller. The media effectively peens the surface leaving small raised ridges. If you mic'ed a piston before and after blasting, it would be a thou or two larger after blasting.
Now if you had real aggressive media, high pressure and aimed at one area for a long time, I'm sure you could wear away the surface as well. |
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Posted: 9/5/2016 8:15:18 AM EDT
[#11]
Quote HistoryQuoted:
I was taught, many years ago, that sand blasting will actually make the part "bigger." i.e. Your pin hole clearance would get smaller. The media effectively peens the surface leaving small raised ridges. If you mic'ed a piston before and after blasting, it would be a thou or two larger after blasting. Now if you had real aggressive media, high pressure and aimed at one area for a long time, I'm sure you could wear away the surface as well. That won't happen with alum ox in that grit. |
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Posted: 9/7/2016 9:50:36 PM EDT
[#12]
Quote HistoryQuoted: That came out with a nice and smooth finish. Are you anodizing before coating or straight to coating? My only experience with blasting is with a coarser media for rust removal (many moons ago). I was surprised how "mild" the 120 AO is. I accidentally shot my hand and it didn't hurt so I aimed it right at my palm and it took the dirt and grease off of my hands. Pretty cool. |
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Posted: 9/21/2016 1:40:55 PM EDT
[#13]
Use 120 grit glass beads at 40-45 psi , hold off about 6" and go in a circular motion and overlap your circles.
That's how we did all the M99 Barrett aluminum receivers after machining. |
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Posted: 9/21/2016 1:55:38 PM EDT
[#14]
Quote HistoryQuoted:
Use 120 grit glass beads at 40-45 psi , hold off about 6" and go in a circular motion and overlap your circles. That's how we did all the M99 Barrett aluminum receivers after machining. No offense but I'd avoid glass bead. It peens the surface versus cutting into it. You want the sharper edges of the alum ox or garnet media for best adhesion. I've coated over bead blasted substrates before, and found noticeably better adhesion with other media blasted surfaces vs glass bead. That said, it will work better than nothing, but hardly ideal. |
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Posted: 10/23/2016 1:38:52 AM EDT
[#15]
So I finally got around to doing some painting this week with my SS Grey Alumhyde II. It went on really easy and did it in 4 coats (2 dust coats and two regluar coats) like the Brownells video said. 3 would have probably done it. I went ahead and media blasted the new parts that were anodized, too. I wanted to make sure all of the surfaces were the same texture so the paint coated uniformly on all parts.
Going with a SS 7.5" barrel and NIB hardware. Should look pretty sweet, I hope.  |
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Posted: 10/27/2016 10:03:05 PM EDT
[#16]
Stainless media
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