Brass filled copper media

[PyroFrank]

Hey everyone! This is my first post here, but I've been reading and learning from the forums for about 3 years now. Anyway, this is what I did today, kind of random but maybe it will be interesting to someone.

 

So I have been in need of some good BP media for a while now, but I didn't want to buy lead balls because they're expensive, and I'd prefer to stay away from lead. I saw in a few threads here the method of filling sections of copper tubing with lead as media, which gave me the idea to see if I could do the same thing with brass since its also heavy and non sparking. My second hobby is casting, so I already have a foundry and equipment for melting brass. I started by cutting 0.7 inch lengths of 0.5 in OD copper tubing. It was the stuff used for gas lines, which is a little softer alloy, making it easy to get through with my pipe cutter.

 

Then I rammed up a blank flask with greensand, which is sand with a binder used for casting.

 

Next I used a 1/2 inch drill bit to hand cut some spaced holes in the sand, and a 1/2 in dowel to clean them up. In the top of the flask you can see I started placing tubes in and pressing a funnel shape around them. I then cut little channels between the funnels. Finally I used a small dowel to compact any loose sand that fell down the tubes.

 

Melting the brass! Just some fittings I got at a scrap yard.

 

Here are the fresh castings after a quick wash. Unfortunately the tubes had a little wiggle room around the brass slugs instead of welding themselves together like I hoped.

 

Then came the boring part. I hacksawed off all the sprues then filed each end flat. The process of clamping the media in my vice squeezed the tubing around the brass, which seems to be holding them in fine. I wanted to minimize comp getting stuck in crevices so I did as best of a job as I reasonably could with the filing. I ended up with 27 pieces, weighing just over a pound in total.

 

This probably took me about 6 hours total of work, which is a lot for what I got, but it was really just an experiment run to see if it would work. I'm probably going to make the rest of my media in this way, but ill set up a bigger flask and do a bunch more at once. Now I know not everyone has access to a foundry, so this really isn't a practical way to make your media. However in my circumstances, it worked out to be a cheaper and lead free alternative to buying it. I haven't milled with them yet, but I'm hoping they will last forever.

 

Whaddya guys think?

[NeighborJ]

Wow that sure seems like a lot of work for milling media. I'm sure they'll work just fine. I'm curious if you were able to get all the sand off. That would be my only safety concern other than the fact that the brass did not bond to the copper, so comp can and will get into those spaces. I would only use these for one dedicated pourpose likely just bp. In order to make a bond to the copper you will need to coat the copper with Boric acid. It is the main ingredient in solder flux. It might have been easier to do one pour, down a single long tube then cut it to .7" slugs. This will also save you the hassle of fileing every piece. If the burrs are still present you could probably just throw the entire batch in the mill until they are pounded smooth. I am a pipe fitter by trade and I also wanted to tell you there is no alloy in that copper. It is the same metal as the hard pipe the only difference is the soft pipe has undergone a process called annealing. This is done by heating the copper till its cherry red and allowing it to cool slowly. I'm not trying to rain on your parade, it's obvious you put a lot of work into those sluggs and it took some skill to make them. I'm confident you will get a system down and will be milling in no time, keep up the good work. Edited August 5, 2016 by NeighborJ

[OldMarine]

Brass would work just fine without the copper and would last longer without the chance of comp hiding in the crevices.

[PIL]

The media looks pretty good.

Here's a tip:

A combination of large and small media will increase your mill efficiency by drastically increase the impact frequency.You may try adding an equal 8mm diameter×10mm length cylinders. The ratio of large and small media depend on the geometry of your milling barrel and the RPM.

[PyroFrank]

Thanks for the feedback guys!

 

Wow that sure seems like a lot of work for milling media. I'm sure they'll work just fine. I'm curious if you were able to get all the sand off. That would be my only safety concern other than the fact that the brass did not bond to the copper, so comp can and will get into those spaces. I would only use these for one dedicated pourpose likely just bp. In order to make a bond to the copper you will need to coat the copper with Boric acid. It is the main ingredient in solder flux. It might have been easier to do one pour, down a single long tube then cut it to .7" slugs. This will also save you the hassle of fileing every piece. If the burrs are still present you could probably just throw the entire batch in the mill until they are pounded smooth. I am a pipe fitter by trade and I also wanted to tell you there is no alloy in that copper. It is the same metal as the hard pipe the only difference is the soft pipe has undergone a process called annealing. This is done by heating the copper till its cherry red and allowing it to cool slowly. I'm not trying to rain on your parade, it's obvious you put a lot of work into those sluggs and it took some skill to make them. I'm confident you will get a system down and will be milling in no time, keep up the good work.

 

I don't believe there is any sand left on them after the filing, but I'll do a dry run to be sure. Is there any safety concern with the sand? The boric acid sounds like a good idea, and I have some on hand. How would you suggest going about coating the tube? Also I see I was wrong about the alloy thing, I knew about annealing but it never occurred to me with the tubing. Thanks for the kind words

 

 

Brass would work just fine without the copper and would last longer without the chance of comp hiding in the crevices.

 

You're right, next time I could just directly cast the brass. I was just thinking I would end up with a lot sand on the surfaces, but maybe that would come off.

 

 

The media looks pretty good.
Here's a tip:
A combination of large and small media will increase your mill efficiency by drastically increase the impact frequency.You may try adding an equal 8mm diameter×10mm length cylinders. The ratio of large and small media depend on the geometry of your milling barrel and the RPM.

 

Ok, if I do the tubing thing again, I'll probably use some slightly larger size to give some variation.

[NeighborJ]

The thing about sand is that if you mix it with most pyrotechnic comps it becomes a sensitizer and that is not good when some of the comps we use are quite sensitive to begin with. This is why we don't use marbles or glass media, accidents have happened.

I do like OMs suggestion of casting the brass w/o the pipe but I fear the sand will be an even bigger issue with that.

PIL is absolutely correct about the different sized pipes and made a huge difference in my mill.

It looked like you used yellow brass in the photo? This should be fine however if you continue the have bonding issues to the cu I feel that red brass will have a closer thermal expansion rate and when cooled should not try to pull away from the wall as much. And finally if this problem persists you can heat them with a torch and fill those gaps with solder (use flux). The Boric acid can be wet with water and made into a paste then coat the inside of pipe. Try to heat the water out of the paste mabe over the forge just before pouring so it's still hot.

I love homemade stuff and it always gives me a sense of pride using them. I know I may be able to buy better stuff but the home built stuff is priceless to me. Your lucky you get to combine two of your hobby's at one go.

[dagabu]

Good read, lots of good stuff here. There is no real way to avoid the cavity that forms when it cools, a generous spru is the best bet but not perfect. I suggest a pinboard with dowels attached and tapped into the sand to form the cavities then removed by pulling after much compacting.

[otto]

One more milling tidbit. Efficient milling is not only dependent on the weight and size(s) of the media.Hardness also plays a part with harder media generally being more efficient than softer stuff. Brass may be relatively soft but is harder than copper and most certainly harder than the softer gas line product you have chosen.

 

As far as the sand issue, I would think that a dry run tumbling with media crashing on media would not only take off some of the sharper edges but remove the lion's share of any residual sand as well. I take my fresh lead for a spin to insure that any small bits that might be knocked off in the initial run don't wind up in anything else that follows.

[NeighborJ]

Copper is a funny metal, even though it will become annealed during the process of filling it with brass it will become hard again as it is stressed and pounded on in the mill. I've often taken soft copper rolls and stretched it out between two beams with a comealong, this creates enough stress to return it to its original hardened state. The brass will also harden under stress only not as much.

[otto]

I am familiar with the phenomenon of work hardened metals. They all do it to some extent. Thing is its all relative to their intrinsic hardness. For example, lead at it's hardest will never be as hard as copper softest and copper will never be as hard as brass. Close maybe, but no cigar. You can also counter any annealing by immediate quenching in cold water while still very hot.

[OldMarine]

If I were to cast my own brass media, I think I'd use at least 200 mesh sand for my green mix to help limit sand occlusions. I'd also water quench them as soon as possible (cut sprues and vents off later) to cause the sand to be ejected from any tiny crevices and pores by the steam flash. I'd then tumble the media with damp rice hulls to pick up any remaining sand beaten from the brass. I've got nearly a ton of mixed red and yellow brass so as soon as I finish my magnalium experiments, I may try casting brass media.

[DavidF]

What does anybody think about the idea of making 'buttons' for media by dropping brass in the appropriate liquid?

[NeighborJ]

I'm not certain the "buttons" would turn out rounded. I catch melted brazing rod in a water filled bucket and it behaves as if it landed on an uneven concrete surface. But a graphite musket ball former would likely work. It'd be nicer then my first milling media, $40 in nickles.

[PyroFrank]

Hey all, sorry to bring this thread back up, but I had a quick question.

 

So as an update on this project: I finally came back to it and casted a bunch more pieces of media, this time using different sized pipes and coating them with boric acid as flux. Now I have enough to fill my harbor freight mill jar, and am dry tumbling them right now to smooth everything out. I checked them recently and everything looks good, to my best knowledge there is no sand whatsoever left on the media. One thing that did happen though, is that some of the pipes still came loose from the brass slugs inside. I hammered these loose slugs out of their pipes, and returned them to the mill.

 

My question is this: If any more of the pipes start to get loose and BP works its way in between the media, could that be a safety concern?

[lloyd]

Eh... "could be", but I'd guess "not likely". The powder trapped in there won't be subject to even as much impact as it would between surfaces of milling balls.

 

You should be milling behind a barricade, anyway. If so, and it blows, all you lose is the jar (and maybe the mill)... but not life and limb.

 

Lloyd