# Glass bead finishing ......



## toolznthings (May 7, 2015)

On my Rupnow Horizontal build Swifty asked about my finish work on my parts so I thought I'd pass on what I have learned.

I found from reading from other forums on blast cabinet techniques that a air pressure of 65 to 80 lbs./sq.in. to more than enough. I run at 65 # , a reading with the gun in operation. Higher pressure degrades the medium faster and really does not do much else. 

Aluminum oxide works for aggressive removing of rust and paint, but much to course for most finish work, especially on our model parts.

Some tips on masking .... Do not plug threaded holes with screws because the glass beads are going to lodged in the threads and you may not get the screws out !  Any oil left in the taped holes is going to trap the glass beads. I use a solvent to wash out the threads and compressed air. I keep old taps to finish cleaning out tapped holes. It's a pain, but a reality.

If you mask off with some type of tape ( duct ) be careful of concentrating the bast at the edges because you can cause some erosion of the metal if its a softer material. It will show after the tape is removed.

You can clean off soft or silver solder over run on joined pieces with care.

Thin parts or sheet can be warped if blasted to hard or in the same spot. I usually hold the part well away from the gun.

Last year I tried a 200/240 grade of glass bead and it really works good for a much softer finish. I normally use Harbor Freight 80 grit glass beads which leaves a nice finish, but rougher than I like for the model parts.  

Here is picture of some brass. One piece has the mill marks and the other was benched before blasting. All pictures using the 200/400 grit.





Some bench work is necessary to remove any marks before blasting or the scratches will show through.

Aluminum finishes great. This pic is benched on one side.




Steel finishes well, also. Left piece half benched. Right piece plan cold roll.




I found that cold blue works great on blasted parts.
Of course steel will rust like crazy sometime after blasting. If I plan on painting the part or not I always use fresh medium. If you have been cleaning other parts the beads pickup " dirt " and can contaminate what you are finishing.

I like to use the following coating and some paste wax on aluminum and steel parts for protection. Works pretty good. ( no connection to product )





Anyone else with other tips chime in !


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## Swifty (May 7, 2015)

Years ago at work, we used a sieve to hold small parts for sandblasting, just gently shake the sieve as you blast the parts.

Paul.


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## toolznthings (May 7, 2015)

Hi Paul,

Good idea for really small stuff. I keep a old scratch pick in the cabinet to hang 
small parts that have a through hole. Will have to make a little basket from something to add to the " tools ".

Brian


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## petertha (May 7, 2015)

Toolz, very nice. Maybe I missed it but what kind of gun are you using & what is a typical min/max diameter pattern? I bought one of these airbrushy types for smallish work but have yet to fire it up. Any feedback or comments?


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## toolznthings (May 8, 2015)

Hi,
I have a Econoline 36" wide x 24" deep blast cabinet which comes with a matching blast gun. All enclosed with vacuum dust collector. Way bigger than the small one you are showing. I have seen catalog pictures of small guns for blasting, but have never seen one work. Would need some type of enclosure to blast in. What are you going to use ? Thanks for the reply.

Brian


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## petertha (May 8, 2015)

toolznthings said:


> Hi, Would need some type of enclosure to blast in. What are you going to use ?
> Brian


 
That's one the reasons its remained in a box over winter. Plan A, assuming the blast media is organically inert, was just step outside my shop door & let the overspray media drop where it may. Plan B was retrofitting one of those big el-cheapo Tupperware-like plastic tote boxes to contain the mess. I'm more concerned by airborne particles making their way to my machines. But I also don't envision large parts. The biggest might be a crankcase to make it look more like a casting & remove machining marks. When I spray my models I wait for appropriate weather conditions in my 'ambient spray booth'.


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## toolznthings (May 8, 2015)

Hi,

Be really careful with the glass beads as they will get into everything unprotected and would quickly ruin a piece of machinery. Outside sounds like a plan.


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## digiex-chris (May 11, 2015)

what orifice size are you using for those 80 grit beads?


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## toolznthings (May 11, 2015)

It's a siphon feed gun in a cabinet blaster. The carbide nozzle is 5/16" diameter and the air jet orifice is 5/32 diameter. Foot operated air valve.


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## digiex-chris (May 12, 2015)

Thanks! I must be in the ballpark then, that's pretty much what I'm using. I'll turn the pressure back down to 70.


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## toolznthings (May 12, 2015)

Hi,

I found the lower pressure works good. Have mine set lower for a few years now with good results. Let me know your results. That setting is with the gun operating, not with gun off.


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