brass media

[zan89]

Hi!

Sorry for opening new topic, but i didnt find nothing much about it.

Now i was using ceramic media, and because of safety reasons(there were some accidents with it, and i know it could spark) i would like change it for brass. What do you think about it from safety perspective and from grinding perspective?!

You will all say use lead..but thats not a question

Thanks for answers!

[Bobosan]

Brass will work.....no spark.

[mikeee]

Brass rod would be a lot easier to cut than stainless steel rod.

[zan89]

I actualy have 13mm rod cuted on pieces.

[Nessalco]

I use brass media and it works fine. Made of a mix of pieces of 1/2" and 3/4" rod stock.

 

Kevin

[zan89]

Hi!

I used brass media and did some experiment, and those were bad.

With brass media was the speed result 3 times slower than with ceramic balls. Time, preparation, everything was the same!

So for me brass is out.. now i have to try with lead balls which will be probably the best!

Edited March 13, 2015 by zan89

[Mumbles]

If brass took 3 times longer you're doing something wrong.

[rogeryermaw]

was your brass rods or spheres? geometry makes a differecnce and has been discussed elsewhere in this forum but only through peoples' personal experiences. i don't think we have any hard data yet.

[zan89]

I had a rod.

I dont know what would i do wrong.

I'm using 3lb ballmill bought on pyrocreations.

probably the shape is problem for bad result!

[drdecibel]

I am in the process of building a mill/tumbler out of 4" PVC with an inner chamber 36" long. Instead of lead I was thinking of using 2-3 loose brass rods 36"

long and 1/2" diameter, thinking that at the right speed (slow) the rods would roll and mill the powder between them. The biggest expense would be the rods (each costing about the price of 100 1/2" lead balls, but if I was to use the setup for other purposes (like rock polishing) it would be easy enough to fabricate extra drums and keep one just for powder use only. I have not figured what the capacity would be but I'm sure I would recoup the cost in a short time. In the past I have used commercial BP, when I can find it but it is in excess of $20 a pound.

 

Any thoughts or ideas?

 

Thanks

[Mumbles]

What you're describing is normally called a rod mill. They're actually pretty good at doing crude crushing to uniform sizes. However, they're terrible for what we want to do. We generally want to grind everything as fine as possible. To do this, you need to maximize the number of media collisions per unit time. 2 or 3 rods is going to have orders of magnitude fewer collisions than a jar full of balls or short cylinders. Accordingly, proper milling will probably take orders of magnitude longer to complete.

 

I've often wondered about using a rod mill to grind charcoal to finer, but uniform sizes.

[MrB]

2-3 rods sounds a lot short as well. The mechanics of a rod mill is the same as the mechanics of a ball mill. You need a rotational speed of 50-95% of critical speed, and 35-65% of the jar volume should be rods. Yeah, i know. The numbers are fairly vague, mainly since they come from an industry where particle (and jar size) isn't really comparable to our uses. So there isn't really that much of direct references to milling reasonably soft materials, in smaller mills. But 2-3 rods barely rolling along the bottom of the jar, isn't right.

B!

[drdecibel]

Thanks guys. I guess I should dig deeper into the physics relating to a rod mill. Since the orientation of the contact surfaces are linear rather than tangental I thought it might be more effective. At least it would be easier to seperate media from BP.

[MrB]

Rod mills are, as Mumbles said, very effective at creating same size particles. You want the same kind of tumbling action in a rod mill as you want in a ballmill, the higher the rod gets before it starts tumbling down, the more force it brings. Slowly rolling along the bottom does very little.

B!