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Tumbling media for detailed brass parts

examo

Plastic
Joined
Feb 26, 2018
Trying to remove some machining marks from detailed brass parts. I have a small vibratory tumbler which I would prefer to use but am having difficulty finding a suitable media, as some of the cuts widths on these parts are as small as 2mm.

I've seen others use small stainless balls to achieve the required results, but as my tumbler is 'light duty' with a 8kg capacity, not sure if I can run this. Only alternative I could find was Porcelain pins but as they seem to primarily be used for finishing, not sure if I could use them for removing the slight machining marks.

Any ideas on a media for this please, or alternatively a different finishing process?
 
Limy, will sand run in a small vibratory mill? Seems like it would be better suited for the type with the sealed ends and "roll" at a low RPM. In the states we can get a small triangle abrasive with angle cut ends. The edges are sharp enough to get part way into narrow grooves.
Ceramic Media | U.M. Abrasives

4th item down are triangles, near the end of the list is a 1/4 by 1/4 triangle in LL weight media. This is one that we use for small details, not sure how far it would reach into your part.
If Limy's silver sand does not work for you, you might find a local source for a similar product. Shipping this stuff to the UK would be cost prohibitive.

There is a "ball cone" stainless media meant for more powerful machines it has a disk that is fairly sharp and could reach into tight features, but it is meant for burnishing and not cutting.
 
If you don't have to deburr, but only remove light machining marks, crushed walnut shell is a classic for brass and other soft metal. It's usually sold as an abrasive blasting medium, but will work nicely in a vibratory machine, especially in the coarser mesh sizes. Don't buy "flour" or fine mesh for this application. Run it dry for least mess.

Wet tumbling with SS pins will give a mirror polish on cartridge brass, probably would work for your parts. Porcelain pins should be at least as aggressive as SS pins, possibly more so. "Wet" by the way, usually means just a slight trickle of liquid.
 
I was gonna suggest walnut shells too, as coarse as you can get for a vibratory tumbler. If it's too sandy it might just pack down around the parts.

When I hear detailed brass, I think fragile- I'd start gentle and work up.
 
If the work s very fine, you can polish with rice, or sawdust as well as nut shell, have a look at the cartridge reloading suppliers.
I have cleaned up heavier brass parts with stainless shot in soapy water, the cost of the shot is terrible, also it is quite aggressive.
 
A easier alternative to Sami's dried sand is block paving sand, i have used it on a fair few brass bits over the years, use to have but lost a really nice jar i would just leave spinning in the lathe over night in low. Half full of parts and sand. Jar had 12 sides so it really helped the stuff move , speed just crank it up till you have a lovely wave of sand - parts happening and then lock up come back later. A fully sealed jar and nothing escapes onto the machine. Just whatch the fine dust when you open it - dig the parts out.
 
Trying to remove some machining marks from detailed brass parts. I have a small vibratory tumbler which I would prefer to use but am having difficulty finding a suitable media, as some of the cuts widths on these parts are as small as 2mm.

I've seen others use small stainless balls to achieve the required results, but as my tumbler is 'light duty' with a 8kg capacity, not sure if I can run this. Only alternative I could find was Porcelain pins but as they seem to primarily be used for finishing, not sure if I could use them for removing the slight machining marks.

Any ideas on a media for this please, or alternatively a different finishing process?


This is what I use.

I sent samples out and the companies sent the samples back and a report listing the media they used.

polishing media small.jpg

I use a pink angle cut triangle media to start with and a white porcelain for polish.

There can be a problem with media jamming in blind holes, through holes and slots. So I use very small media that falls out, or larger media than any hole or slot so it cannot go in.
 
After messing with walnut media for my brass cartridge cases and getting a dirty appearance on the surfaces I finally bought a few pounds of stainless shot. This, a couple pounds of it with half a quart of water and few drops of Dawn brings a bright luster to the cases. If I deprime first they stainless rods in this shot media gets in and cleans out the pockets. I'd like to make an automatic deprimer and do that every time I run a few thousand rounds.

Not meaning to hijack, but does anyone have a formula for highly polishing aluminum? The last thing I tried was the same stainless shot in a rotary tumbler, it left a microscopic coating on the parts, made them look dull gray.
But that was with microfine AO powder added. What a mess! Previously I tried polypropylene beads with the same superfine AO, not much better. That was in a vibratory tumbler.

I'm hoping for a way to get a bright "Chrome" like polish without using a cloth wheel. But with the wheel what stick is used? All I have is Chromic Oxide, "Green".
Any help appreciated.
 
maize.jpg




For aluminium I have used maize granuals and added some Brasso, but it does dry out to a lot of dust in the maize after a while.

Not tried walnut shells, one reason is I have a lot of holes some down to 1mm about 13mm deep the maize can get into the holes and is a sod to get out, have to pick it out with a small drill in a pin chuck, so always steered clear of walnut shells as they may be harder to pick out, some I have to drill out by twisting the drill as well as poking.

Edit to add photo.
Also on second thoughts I forget if this is ground maize or corn cob?
 








 
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