Dumb question Cobb media

[TaylorS]

So I have a small batch of 44-40 that I threw in the tumbler yesterday with new Cobb media. Remembered the tumbler was running 27hours later and ran out to shut the tumbler down and pull the brass and the Cobb turned to cat litter. I don’t think the brass was that dirty, maybe over cooked it? Last I can recall using it I got 2 or 3 runs out of a tumbler of media.


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[Dadswickedammo]

I get 100s of runs with walnut.

[country gent]

What corn cob media were you using? I buy mine in 50 lb bags for blasting and get a lot of use on it. I also treat mine with nufinish and iosso brass polish. a little alchlol or mineral spirits to keep dust down. I usually have 3 loads of media going at time.

1st is the oldest used for super dirty brass or polishing parts Ive made this stuff is dirty to start with. Its been thru the first to cycles already. But cruddy range brass is about all it sees.

2nd is the next to oldest used on brass I have fired and or other semi clean items. This is on its second step. It shows some use but isn't overly dirty and does a nice job polishing

3rd is the newest and is used for that final polish on brass that needs to look good. Its pretty clean and treated *** above and the polishes are building up as its used. Only precleaned brass is put into this.

When 1 becomes to dirty to work with 2 becomes 1. 3 becomes 2 and a new batch is started for 3. I bught my last 50 lb bag of media ( I think it was 20-20 grit) 15 years ago and its just under half full now.

I normally run the preclean with a fll load for 4-6 hours, this comes out with dirt and crud gone and a light polish. Then the final polish is 2-4 hours in the new media and treatment. This comes out very bright and shiny and the cob hasn't changed visibly here.

[D Crockett]

try putting a bounce the kind you put in the dryer when drying your wash it helps to add life to the media D Crockett

[Rcmaveric]

If i don't put the used bounce sheets in there it mucks up the walnut media quickly in a few runs. One sniff of that dust has me tasting pennies for the rest of the day. The dryer sheets help it look cleaner longer and controls the dust.

[ReloaderFred]

A used dryer sheet works better than a new one. The coating on the new ones tends to clump up.

I buy my ground corn cob in 40 pound sacks from zoro.com for about the same price the pet stores sell 10 pounds for. They pay shipping on $50.00 orders, and since they're owned by Grainger, it's easy to make an order up for the free shipping. They offer two grades under "blasting materials", 14-20 and 20-40. I use the 20-40, since it's fine enough that it doesn't get stuck in flash holes and have to be pushed out.

I run three tumblers most of the time, with two doing the rough cleaning, and the third doing a final polish with some car wax mixed in to preserve the high luster. In the first two tumblers, I use Berry's Brass Polish, which I buy in the quart size, which is more economical.

The ground corn cob should last you hundreds of rounds of brass, and leaving it running for 27 hours shouldn't make it clump up, unless that brass was fired with a black powder substitute......

Hope this helps.

Fred

[TaylorS]

I usually use walnut but have a bag of Cobb and therefore used it it was just odd to me that it went from yellow to gray like that with just that one run


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[mdi]

There is a difference between blast media and pet litter. The size, hardness, and overall quality of blast media is closely controlled and pet litter seems like left over scrap. I use corn cob blast media many hours and just add a bit of auto polish/wax to new media, nothing else is needed (I only use the polish for the light wax coat for tarnish protection). I got a 40 lb bag from Drillspot a few years ago, but am unable to find their site again. Try Grainger, McMaster Carr, etc. for "blast media, corn cob"...

[RogerDat]

Maybe the long run really cleaned the inside of the cases more than usual. I find an hour or two in dry tumble cleans outside fine, knocks the worst of the inside crud off but doesn't really clean the inside. Just ran 500 federal .38 special cases that were well polished in dry media (not 27 hrs clean but cleaned) When I gave them one hour in wet tumble with pins the water came out black, and the insides were shiny. So I know that a normal run in the dry media that would leave the outside all shiny still leaves a whole lot of gunk inside the cases. Maybe your long run got that all out?

[country gent]

Blast media has the soft center of the cob taken out and only the hard outer left not sure on the pet litter as that center portion is also very absorbant and would be a plus. We used corncob media, ceramic media, and shot in the big tumblers at work for light polishing and burr removal of stamped and some machined parts. Here the corn cob was given a measured amount of polishing oil to help. the ceramics were in a soap water mix and the shot was in a water mix. a vibratory machines was used to separate the parts. These were rotary polishers the size of a cement mixer. Throttle plates, injector parts were ran thru this cleaning deburring polish process before assembly.

[sigep1764]

I haven't replaced the cob media in my tumbler for a couple of years. Easily 20000 9mm cases. Maybe I'm doing it wrong, but with some Mothers Wax in there every couple of batches, the brass comes out shiny as always. When I change I did change it, I remember it was dirty as **** after one batch of brass. Ill replace this summer now that you guys have reminded me. I do place a dedicated Terry towel over the tumbler as it runs to cut down dust.

[Soundguy]

try putting a bounce the kind you put in the dryer when drying your wash it helps to add life to the media D Crockett

ditto that. I get many, many runs.

and if I get really dirty range pickup, i run them in cheap white rice then toss that to the ants or birds.

[TNsailorman]

I no longer use anything but lizard litter from the pet stores. I rally cleans and last quiet a while before needing changed out. I also use a small bottle cap of a mixture of mineral spirits & Mother's car wax in it. Brass comes out bright and shiny after a couple of hours. james

Forgot to add: If the brass is really dirty/corroded, I put it in a acid bath for about 30 minutes, rinse in water, dry and then put it into the tumbler.

[Gee_Wizz01]

About 4 years ago I finished off a 25 bag of corn cob media that I bought in 1993. I know I polished more than 25,000 rnds of 9mm, 45 ACP, 45 Colt,30-06, 7.62x39 and various other calibers. I was a serious brass scrounge and I had plenty of filthy range brass. Even then I would get at least 1000 rounds out of a load of corn cob. Around 2002 I started using walnut media for really dirty brass and finished up with corn cob for the sparkling shine. All this time I used either FA or Dillon brass polish. In 2008 I started cleaning my match brass in my Ultrasonic cleaner with Lemishine annd Dawn . The US cleaner was fast and did a great job, but my 50 rd batch size made the job slow and tedious. Last year I finally bought a FART and a case dryer and never looked back. Now I only use my corn cob media to give an ultra bright finish to my match brass.

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[Soundguy]

Racing stripes! ( shiny brass ).

[lightman]

I also use the 20-40 grit and use it over and over. I add a cap full of mineral spirits and a splash of car polish, run it enough to get it mixed and add my brass. A dryer sheet worked well for dust control before I started adding the mineral spirits. I bought my corncobb from a company called Drillspot but it shipped from Grainger. I think Zoro does the same thing now.

[country gent]

I don't go by the "looks" of the corn cob media, but by the polish time required to bring brass to a clean bright polish. New treated corn cob may take a couple hours to fully polish when this time starts to extend I move it to the next spot of use and start with new.

[mdi]

I've seen "Cobb" a couple times lately. Is this a new product/trade name "Cobb Tumbling Media"?

[lightman]

I think mine was a product of spell check!

[mold maker]

Walnut media is more aggressive to remove crud from tarnished brass. Corn cob has a polishing quality beyond Walnut. I now use SS pins with Dawn and citric acid to remove anything objectionable and cob for a final jewlery polish. One advantage is the cob lasts forever and there is no contaminated dust.