Cheap ball mill. Why did the lids warp?

[Coyote]

I've graduated to something bigger, but back in the day when I used a generic and tiny ball mill with steel or ceramic media, the lids of the ball mills always ended up warped. Being me, I tried duct-taping the lids on (!!), but that only lasted me so long until I couldn't mill anything anymore.

 

These days I'll just buy black powder if I need to, and I'll always fondly remember the sting of getting black powder into cuts on my fingers (ouch), but I wonder why. Why did the lids warp? They ended up too large and oddly shaped. Was this the fault of the media/black powder? Or the tumbler itself?

 

I don't want to develop a black powder obsession at the price of actually getting to build fireworks, but I still need to know.

[OblivionFall]

Perhaps the ball mill wasn't graded to handle that load and overheated, warping the rubber lid?

[mikeee]

What kind of jar/lid?

A little information would be helpful. :-)

[calebkessinger]

They build heat.. which builds pressure..

[tradami]

Invest in a nice mill. Or build one.

 

Shortcuts often cost more in the long run.

[MWJ]

Was it a Harbor freight mill?

[Strommashina]

Here is a useful service in selecting a ball mill. Try it Performance calculator for ball mills based on dry milling method

[WindowLicka]

Was it a Harbor freight mill?

 

I don't see a rubber HF tumblers lid warping. Although I have been wrong before. It's a metal lid covered with rubber on a rubber can so probably some other generic.

Edited June 9, 2016 by WindowLicka

[PhoenixRising]

I do notice a small pressure build up in the HF mill, albeit very small. It's likely due to the slight temperature increase of being run. I can tell because every hour I would stop the mill and tap it down a bit to prevent clumping, but I will also slightly open the lid to release any pressure. If you crack the lid right away it will poof a little powder out, but if you wait about 10 minutes it does nothing, indicating that cooling off reduces pressure and prevents this from happening. Don't get me wrong, it's only a very small amount of pressure and it's never been an issue, but I still stop every hour or 2 and release the pressure and tap it all down. So far everything's been great for the past couple years and I think the HF should last a bit longer, I've only oiled a couple times. Lid is fine as is the rubber everywhere on it.

 

Now, I'm willing to bet you could warp the lid on a HF by tightening the nut down too much. I remember to tighten it down enough that I can turn the milling jar by the nut while holding it in my hands. Once the nut it tight enough that the whole jar will turn with it, just kind of snug it a little more and you're good to go, at least in my 'limited experience.'

Edited June 13, 2016 by PhoenixRising

[FelixLiu]

This may be the cause of the raw material.