Does anyone know what this is?

[BHGiant]

Came across these at the local scrap yard. Girlfriend says they are probably ball bearings but they look too irregular in shape. Anyone have insight? 

 

these look like they've been in concrete almost

[Frosty]

They're mall mill balls, they do the final crushing and mixing for material that needs to be a fine powder like Portland Cement, garden lime, etc. 

Frosty The Lucky.

[George N. M.]

Ball mills work by putting the material to be crushed and steel balls in a rotating drum.  As the drum rotates the balls fall against each other and crush the material.  There is usually water flowing through the drum to carry the crushed material off.  The balls gradually wear down to a smaller diameter and have to be replaced.  Ball mills are LOUD!  I'm not sure about the type of metal used for mill balls.

"By hammer and hand all arts do stand."

[arkie]

Often, you can find ball mill balls at antique stores and flea markets being sold as antique Civil War (or older!) cannon balls and getting exorbitant prices for them...use caution when purchasing them as such.

[ThomasPowers]

I was at the fleamarket once and on one aisle a fellow was selling mill balls for US$1 apiece and the next aisle over a guy was selling the exact same items as cannon balls for $20 a piece.  A good way to tell the difference is to measure them. Cannon sizes have been standardized in various armies for centuries and it's easy to prove that the items in question don't match anything used!

They are excellent for making ball stakes from but are usually hard tough alloys and so don't forget preheat post slow cool!

Local SCA armour makers would love to know about that stash!

Note: as mentioned, they can start out HUGE and gradually wear down until they are no longer effective.

[HojPoj]

More interestingly, they can wear unevenly.  I recall seeing at some cement manufacturing plants a number of old ones laying about, they were lumpy, egg shaped, or looked like meteorites.  The ones in the pictured stash appear to be in pretty good condition.  At one point I was looking for some to use in making a muller for sand casting but couldn't locate a plant in my area.

[ThomasPowers]

AZ has a lot of mines with ores that need crushing for processing.

[BHGiant]

This is all fascinating! Excuse my excitement but I love seeing old pieces of machinery or things like this and figuring out what they were for.

1 hour ago, ThomasPowers said:

Local SCA armour makers would love to know about that stash

Thank you for this.

1 hour ago, ThomasPowers said:

AZ has a lot of mines with ores that need crushing for processing.

We aren't called the copper state for nothing!

1 hour ago, HojPoj said:

At one point I was looking for some to use in making a muller for sand casting but couldn't locate a plant in my area.

I'm interested in what your setup would have looked like. All the mullers I've seen so far all use a grinding wheel of some kind in an upright bucket.

[pnut]

Tumbling media. I used to work at a company called Sweco that manufactured agitators, tumblers, and the media to be used with them. 

Pnut

 

[HojPoj]

BHGiant:

There's another type (a bit less effective) that uses a- or a couple, large weights that tumble inside in a drum to do the compaction/smearing of the sand, and a scraper takes it off the walls.  As far as what it *would* have looked like, think a cement mixer style drum made from a 20lb propane tank.  Only reason for doing that vs. the wheel style muller is that the wheel style can require a lot more torque and lower speed (I would have a hard time sourcing an affordable gearbox to do the job).  With the stuff I had I could've used jackshafts and pulleys to get a low enough speed and sufficient torque to do the job.  At this point I'm just gonna have to give up on sandcasting so that project never had enough priority to go any further.

[Kozzy]

Yup, ball mill balls.  They're typically extremely hard material and usually contain a lot of manganese similar to abrasion resistant plate/welding wire and such.  Pulverize whatever material you toss in the tumbler, generally down to a talcum fine power.  Some small hard rock gold mining operations use a "miniature" ball mill to turn ore into powder so that the gold can be chemically extracted.

One weird application is dust mites.  Dust mites are everywhere in your environment, eating the dead skin you sluff off.  With that exposure, may people become allergic to dust mite protein.  The "cure" is a series of allergy shots to expose one to increasing doses of the protein and desensitize the patient.

The protein is derived from mites (at least initially) and those critters are tough as nails.  They are crushed in a ball mill. However, they are so tough that they survive a regular ball mill so a pressurized ball mill is used--they take the air pressure inside up to about 5000 PSI which pre-stresses the little critters enough that the balls can break them up.  They normally survive both the balls and the pressure but with both, turn into a nice slurry to make testing meds from.

FYI There is also a "bar mill" where instead of balls, they use round bars in the tumbler.  Imagine a bunch of heavy shafts laid crosswise in a tumbler.  In some cases, bar mills can be more efficient because the overall contact surface area with the product being crushed is higher and the bars have more weight than balls. 

[George N. M.]

Kozzy:  Because of my background I have a slightly different nomenclature.  As a young man I worked for U.S. Steel in the "bar mill" where we produced square bars for shipment to customers.  As a geologist I worked at a flourite mine which used a "rod mill" to crush the ore for concentrating.

"By hammer and hand all arts do stand."

[Kozzy]

10 hours ago, pnut said:

Tumbling media. I used to work at a company called Sweco that manufactured agitators, tumblers, and the media to be used with them. 

Good point.  They also but the balls on some vibratory screens to keep the product sifting through. Without the balls "de-clumping" it can cake on top of the screen.

[arkie]

10 hours ago, ThomasPowers said:

AZ has a lot of mines with ores that need crushing for processing.

When I was in my geology summer field camp at Salida, CO, we took a field trip up to the Climax Molybdenum Mine near Leadville.  We got a tour inside the mine and the processing plant(s).  They were using balls in the ball mill to powder the ore for processing that were about the size of a cantaloupe or small watermelon.  Outside the milling plant, there were stacks of used balls as big as large houses, destined for scrap.  The noise inside the ball mill plant was unbelievably deafening!  A bunch of us wanted to take some mill balls home as souvenirs, but they wouldn't let us.

[pnut]

On 7/17/2020 at 2:20 PM, Kozzy said:

 They also but the balls on some vibratory screens to keep the product sifting through.

That's what I meant when I said agitators. Agitation screening. I was trying to word it so it couldn't be confused for something else. Most of the media used in the tumblers we produced looked like thick jacks or caltrops. Like twisted X's but we made all shapes depending on the application or whatever the customers wanted. 

Pnut

[BillyBones]

We use a tumbler for deburring parts in the shop i work in. The parts i make are rarely more that 3/4" long and usually less that 1/2" wide, small stuff. We use things like pnut mentioned jacks or caltrops, but also trapezoid, round , square, triangle, etc. They are also usually ceramic. 

[Kozzy]

One thing I should add about these larger "rough" balls--and another style that is similar which was used as a large bearing in old grain combines.  People find them in various places and then try and sell as "cannon balls" at ridiculously high prices as though they are something special.  Since the smithing world often digs through scrap offerings, it's just something to be aware of if you run into someone who is ill informed.  It's rarely someone trying to intentionally deceive--at least in my experience.

I have a dozen of the combine version (they are close to a 2 lb actual cannon ball in size) rolling around in the back of my truck right now looking for an "art" project to be used in.

[Scott NC]

Lifetime supply of scrap art eyeballs.  Possible trebuchet ammo.