Media Blasting Question

[oliveview]

Hi all:

I apologize, if this isn't the best location for this question. Not sure where I might post this, so I figured the knife-making section would land the most experienced eyes.

I'm doing some basic rehabbing and refinishing, on various knives (and some old guns, too) and there's one thing I'm having a hard time duplicating. It's the smooth, fine bead-blast finish on many pieces and parts.
I have some medium grit ground glass beads from Harbor Freight, however, that tends to give a harsher, more "toothed" finish to materials like titanium and aluminum. Almost the same as the more abrasive aluminum oxide.

Is my problem that the media is already ground - therefore more abrasive? Do I need to seek out smooth, round glass media?

Thanks!

P.S. My pressure and technique are conservative. Never more than about 90psi.

 

[i4Marc]

I have to sandblast a blade soon so I am looking forward to hearing some of the suggestions.

 

[Daniel Fairly Knives]

I like Garnet sand. The finish just keeps looking better as it breaks down. It will blast aggressively with lots of texture at first then eventually break down and give a darker finish.

 

[oliveview]

I like Garnet sand. The finish just keeps looking better as it breaks down. It will blast aggressively with lots of texture at first then eventually break down and give a darker finish.

Thanks for the input. I'm already achieving a variety of aggressive finishes. But that's what I'm looking to avoid, in many cases. I'm pretty certain the issue is as simple as the fact that I'm only using "ground" glass. Not smooth glass beads. I'll need to order the smooth online. The only question, is what fine/course grit level?

 

[REK Knives]

If you are wanting a polished smooth finish then you are looking in the wrong area... You don't need to figure out blasting media but rather tumbling media. Yes, welcome to what I have been going through recently... And get ready to spend some money hehe. You will need to have a good tumbler and the right media and burnishing compound. Now that I've pointed you in the right direction, you should be able to start researching it via Google 😊 I'm currently going to be experimenting with different media to figure out what I need for what I'm wanting.

 

[oliveview]

If you are wanting a polished smooth finish then you are looking in the wrong area... You don't need to figure out blasting media but rather tumbling media. Yes, welcome to what I have been going through recently... And get ready to spend some money hehe. You will need to have a good tumbler and the right media and burnishing compound. Now that I've pointed you in the right direction, you should be able to start researching it via Google 😊 I'm currently going to be experimenting with different media to figure out what I need for what I'm wanting.

Thanks, but I fully realize the differences between the processes and results. A tumbled "working" finish isn't what I'm worried about (in this case) - even though you're certainly correct, that it can also provide a nice finish. But it has nothing to do with media blasting. Totally different process, abilities, and results. Plus, because I'm rehabbing certain items which are already bead-blasted, that's the same finish I'll be putting back on.

 

[REK Knives]

Thanks, but I fully realize the differences between the processes and results. A tumbled "working" finish isn't what I'm worried about (in this case) - even though you're certainly correct, that it can also provide a nice finish. But it has nothing to do with media blasting. Totally different process, abilities, and results. Plus, because I'm rehabbing certain items which are already bead-blasted, that's the same finish I'll be putting back on.

Ah ok I must have misunderstood your question.... I guess I read into it you were wanting a polished surface when I read "smooth, fine". So you're using glass beads and not crushed glass right now?

 

[oliveview]

That's the issue. I have been trying "ground" glass media from Harbor Freight, as that's the only retailer nearby which sells that kind of thing. The resultant metal is almost indistinguishable from the very rough finish you would get from aluminum oxide, or garnet. I simply made the assumption that glass would be glass...wrong! Online, I can clearly see that there are a wide variety of "smooth" round glass bead options, with a multitude of grit finishes. Only issue being, I don't really know what grit level I should get, and the costs are pretty darned high.

 

[REK Knives]

That's the issue. I have been trying "ground" glass media from Harbor Freight, as that's the only retailer nearby which sells that kind of thing. The resultant metal is almost indistinguishable from the very rough finish you would get from aluminum oxide, or garnet. I simply made the assumption that glass would be glass...wrong! Online, I can clearly see that there are a wide variety of "smooth" round glass bead options, with a multitude of grit finishes. Only issue being, I don't really know what grit level I should get, and the costs are pretty darned high.

Well I do know anything over 120 grit is considered fine.... So try to get something above that and see what happens. Sorry I can't help more!

 

[oliveview]

Well I do know anything over 120 grit is considered fine.... So try to get something above that and see what happens. Sorry I can't help more!

Right on. Thanks!

 

[woodwrkr221]

I've done some pistolsmithing on 1911's in the past including bead blasting stainless steel. Most of the pro pistol smiths will use smooth glass beads at 120 grit or higher and quite often they will use lower air pressure, down around 70 psi or thereabouts.

Technique matters also. The closer you hold the nozzle to the work piece you're bead blasting the coarser and streakier the finish will look.

Also, if you're bead blasting stainless steel, never use media that has ever been used on any type of non-stainless steel not even if it was only just once for a small piece. Keep a special batch of media that is reserved for stainless and nothing else. Mixing media will result in rust specs imbedded in the surface of your stainless steel.

 

[oliveview]

I've done some pistolsmithing on 1911's in the past including bead blasting stainless steel. Most of the pro pistol smiths will use smooth glass beads at 120 grit or higher and quite often they will use lower air pressure, down around 70 psi or thereabouts.

Technique matters also. The closer you hold the nozzle to the work piece you're bead blasting the coarser and streakier the finish will look.

Also, if you're bead blasting stainless steel, never use media that has ever been used on any type of non-stainless steel not even if it was only just once for a small piece. Keep a special batch of media that is reserved for stainless and nothing else. Mixing media will result in rust specs imbedded in the surface of your stainless steel.

Excellent advice. Thanks. Yes, I'm well aware of cross-contaminating stainless, with carbon steel residue. While I've refinished fewer pistols that way, I know that's a major quality control. Most often, I've focused on brushed satin, because I love to bring old S&W revolvers back from the dead. But whatever improved technique I employ for smooth blasting knife parts, will translate right into some "Pro Shop" type revolver finishes, as well.

 

[Daniel Fairly Knives]

Thanks for the input. I'm already achieving a variety of aggressive finishes. But that's what I'm looking to avoid, in many cases. I'm pretty certain the issue is as simple as the fact that I'm only using "ground" glass. Not smooth glass beads. I'll need to order the smooth online. The only question, is what fine/course grit level?

I'd try around 120 grit glass beads to start... the garnet I mentioned would also be good around 120-180 grit for a smooth finish.

If you don't mind a tumbled finish the tumbling will smooth things right up even from a low blasted grit... your finish better be good pre-blast but this will smooth it up nicely.