Vibratory Tumbler Polishing

[dencins]

For the past year I have been experimenting with vibratory tumbling brass parts as an alternative to buffing.  I could not find much information how to vibratory tumble so I thought I would outline what I have found.  I have been using a relatively cheap 18# vibratory tumbler from Harbor Freight (Harbor Freight has a 5# model and an 18# model).  The things that were most confusing to me was type of media and how long to tumble.

After trying several types of media I settled on a three step process used by the jewelry industry.  The first two steps use plastic pyramids filled with fine silica cutting abrasive (Dark Green is for cutting and Light Green is for polishing).  The third step is Dri Shine which seems like crushed corn husks with Simichrome added for polishing to bring the parts to a high luster.  The media, Soap Powder and Simichrome were purchased from a local supplier of jewelry making tools (Contenti).  Kramer Industries is another source frequently mentioned.

The basic rule is to use a ratio of 10 parts media to 1 part of items to be tumbled.  I use 10# of each media.  I did purchase two additional tumbling bowls so I could just change the bowls.  Running a mix of different parts at the same time has not been an issue.  If the parts have severe pits, scratches, etc. I sand the parts before vibratory tumbling.  I suspect the vibratory tumbling would work but the cycle times would be extremely long.
 
The first step is the cutting step and I run the Dark Green media for 6 - 8 hours.  I mix about two teaspoons of Soap Powder to 8 ounces of water and add it to the 10# of media.  The Soap Powder allows the parts to roll easily in the media and collects dirt and metal removed during the process.  The goal of this step is to take out any tool marks or rough surfaces.  When done the parts should have a smooth matte finish.

The second step is like the first step except the media is Light Green and I run it for 4 - 5 hours.  A new mix of Soap Powder is used for this step.  The goal of this step is to get a smooth, bright finish.     

The third step uses Dri Shine and I run it overnight (around 12 hours) although it probably can be run less time.  No Soap Powder is used for this step.  The Dri Shine can be refreshed by putting some Simichrome in it (although I am not really sure how much).  The parts come out looking like they have been buffed to a high shine.

The big advantage I have found is getting the equivalent to buffing without the hands-on time or mess of buffing.  Once the vibratory tumbler is loaded with parts it runs by itself until the step is complete.  Hands-on time is needed to separate the parts from the media and load the next step but that is minimal.  I use a piece of 1/4" screen to separate the parts from the media.

Today I purchased a second 18# vibratory tumbler from Harbor Freight.  I have become dependent enough on it I wanted a backup.  The list price is $199.99 but it is on sale in June for $164.99 plus I had a 25% off coupon that was on a Harbor Freight flier so I got it for $123.74 plus tax.

A difference between the HF unit and the more expensive units is the motor.  HF unit has sleeved bearings while the more expensive units use ball bearing motors.  There are also some units that have a belt drive while the HF is direct drive.  These differences would suggest the expensive units should outlast the HF.

Dennis Hallworth
       

[unbeldi]

What is it that you are finishing?
I thought the tumblers have to be pretty full, like half full or more, to have good results.  What is the volume of your tumbler?

I think in addition to finishing agent ("media") and time, it also matters what the vibrational amplitude and frequency is, to determine degree of polish.

[dencins]

Most of what I am doing is pre-plating preparation.  On telephones this can range from screws, hinges on subsets, gongs, some candlestick parts, etc.  I also have used it to clean old automobile parts, clock parts, brass belt buckle, antique door lock, etc.

I use 10# of media in an 18# capacity bowl.  This fills the bowl somewhat over half full with media.  The ten pounds of Dri Shine fills it slightly more.

Since I bought a vibratory tumbler and was not designing one, I focused on the things I could control.  There are many vibratory tumblers on the market that run from the very low end like mine to machines that cost thousands of dollars that would polish parts much faster.  I wanted a low cost machine that would work and be affordable for a hobbyist.

I have heard vibratory tumbling is also used to polish plastic but I have not tried it.   

Dennis Hallworth 

[Sargeguy]

I use a Lortone rotary tumbler which does a great job cleaning small items or rust and crust.  The barrels have a 1lb capacity and I fill them with steel shot, water and dish detergent.  I have the polishing media but have never used it for that purpose.

[benhutcherson]

I recently bought a 5lb Harbor Freight model, primarily for cleaning cartridge brass but had thought about using it for other purposes like polishing brass gongs in telephones(as many here like to do).

I use walnut media "spiked" with a commercial brass polish(in my case made by Berrys, but there are many on the market) as well as some green liquid Turtle Wax car polish. As I said, I've only used it on cartridge brass, which gets shiny but not to a mirror polish. I suspect that the finish I get would not give acceptable results for plating. I've been told, however, that corn cob media will give more of a mirror polish.

[cloyd]

I have a small rotary tumbler arriving in the mail soon.  From reading your posts, I think that a wet polish with detergent, water and possibly with the stainless steel shot/or dark plastic pyramids for step one followed by light green and then a dry polish with walnut shells or corncob/simichrome would do a good job.

I use a Lortone rotary tumbler which does a great job cleaning small items or rust and crust.  The barrels have a 1lb capacity and I fill them with steel shot, water and dish detergent.  I have the polishing media but have never used it for that purpose.

Sargeguy,
I need some specific recommendations on the size, variety, and vendor for the stainless steel shot.  The per pound price varies by 100%.  Is that just a high markup or is there "cheap" s.s. shot that I should avoid.

Ben, the corncob media sounds like what I would need to use as a final step on the gongs. 

dencins,
Thank you for such a detailed report on your experiences with the large vibratory tumblers.  Have you tried tumbling metal and bakelite phone cases?  The lighter weight plastic pyramids might be safer on a bakelite piece.  Would it ruin the threads on a receiver cap?  Have you tried this?

What are your thoughts?

Tina

[Dan/Panther]

Midway Reloading supplies sells a tumbler with extra baskets. They are used to tumble and polish brass casings. I use one tumbler with ground walnut shells, overnight. Then switch the brass to another basket with corncob and brass polish. Both are available in bulk. This takes used cartridge cases from dirty, and dull, to mirror shine in two steps.

D/P

Tumblers- http://www.midwayusa.com/product/103614/rcbs-vibratory-case-tumbler-110-volt
Scroll down page for other models.

Medium-  http://www.midwayusa.com/s?userSearchQuery=tumbling+medium

[cihensley@aol.com]

I used mine several times for 302 gongs. It worked fine for the outside of the bells, but hardly touched the interior surfaces.

Chuck

[unbeldi]

I used mine several times for 302 gongs. It worked fine for the outside of the bells, but hardly touched the interior surfaces.

Chuck

Well, brass bells should be oxidized anyways, I don't think they were ever shiny.

[Sargeguy]

I use 1ib. stainless steel shot that I purchased off of eBay in a small Lortone rotating tumbler.  Make sure to get stainless steel shot.  Add water so it just covers the shot, add a little dish washing detergent, and tumble the item overnight.  I sometimes add a 1/2 teaspoon of Oxiclean.  This will remove much of the dirt, grime, and surface rust or oxidation while preserving the patina on most metals.  The parts come out with a semi-gloss finish usually. 

[19and41]

One bit of advice in cleaning brass and aluminum products is to avoid products containing ammonia.  It can blacken aluminum and can cause brass items to become brittle