That's the great thing about experiments, there is never a failure. You will learn something either way. A lot of porosity. I look forward to the next experiment.
The journey continues. I expect to try this in about 3 months when it warms up enough to get back into my shop. Your efforts will save me a lot of time and gas. Odd how the internet does not have much info on the process. I've watched Clickspring for years but Chris doesn't go into detail about it. Hang in there.
Try doing a slower pour to give the gases a chance to work out of the pour. In a deep mold the only way for the gases to go is to the sides and form pockets. if poured too fast.
The Swiss are renowned for their holey cheese. 🧀 Rob has perfected the equivalent in brass. Stay tuned for the next installment of "The trials and tribulations of Rob Here-Again". Coming soon to a screen near you. 👍
There is a retired molder on RU-vid who goes by Sandrammer. He has a good video of how to set up a mold to pour good quality machining stock. If your mold and its lack of any gating system is part of the problem, maybe some of his instructions could help. I haven't poured much brass, just lots of aluminum and bronze, but I do know that molten metal free-falling more than a really tiny distance (like a cm or maybe 2) causes oxide films to be generated by turbulent flow and entrained into the metal, where they can cause defects like you are seeing. No promises, but I hope this helps!
Add oil to the cylinder you are pouring into this will help it to solidify at a even rate and add borax right at the end before pouring after removing slag.
I was sure you would get to much scale forming on those threads for those nuts to come off! Then when they came off okay, but you struggled getting the cap off - I thought maybe you had done a wonderful job of brazing on the end cap anyway - The suspense levels were high in this video! :)
Hi Rob, been following along with your trials, I like your approach, I have nothing to add as it's not my field of experience, however, if you continue as you are, only ever changing one variable at a time, I am pretty sure you will crack it very soon and be producing very useful stock, you are nearly there already to be honest. Furnace is spot on, well done. Cheers, Jon
Hi Jon, yes it's the same path as learning how to cast aluminium. You try all this stuff and quite frankly some of it is old wives tales. Got there in the end OK, but brass behaves very differently, so it's start from scratch time again. It will all work out eventually. Interesting trialing stuff and I wonder if people are getting sick of this subject, but the numbers are still up. So I will probably shoot some more video. Cheers Rob
I think you're making good progress! Just a couple of thoughts... try casting ingots first and then making a final casting with cleaner brass. Also a Crucible with a rounded bottom so you can clean the dross easier in the primary melting. Also a larger sample of brass in your Crucible will help even though you're casting small parts. Great job!
Making ingots to re melt is never good with brass, it doesn't clean it, it just boils some of the zinc out of it, I never keep re melting brass over again .& not easy making sound barstock. keep up the good work.
Hi Rob , I have been enjoying the process as it is something I really want to do. Have had other things that seems to get in the way but will eventually get there. I'm sure wondering if your mold didn't get to hot. It needs heat I'm sure but where you had it it could be hotter than the brass was and could cause issues with the brass when poured. It is one change that you added and may have something to do with the cavitation of the brass that was there and I don't think it was from the flux. I wondered when you made the furnace about the size of the chimney hole as you had mentioned but it seems to be plenty big. I also wondered that if swinging the lid sideways was necessary but you mentioning the heat factor working with it and that could sure make a difference I bet. Sure glad you are doing this and showing it and doing brass now as it is sure going to save me a lot of trial and error when the time comes for me to be able to do this. One more thing is are you happy with the wheels as it looks like it is quite necessary as well as the handle with the design you have but room is always a problem so appreciate your thoughts. Thanks for the videos. Dale in Canada
Hi Dale, the wheels are definitely necessary due to the weight. The removable handle works well and moving it is a snack. The design is perfect IMHO and I wouldn't change any of it. The Perlite 4:1 ratio appears to be stronger than the 3:1 ratio I used in the base. I will do some more experimenting to get the best pour result. Cheers Rob
I had a big fail when I tried borax as a flux when melting (lead) type metal for my type casting machine. Never again. Very enjoyable watching your experiments. Andrew 👏👏👍😀
This has been great to follow. I wondered what flux options you would try. I believe borax reacts with zinc, maybe that reaction offgassing is the cause of the internal cavities. Have you got any plans to try candle/paraffin wax or beeswax as a flux?
I think half the impurities are from the old stuff in the crucible. You need to make a new set, one for brass, one for aluminium and one for lead. Try as well adding a little scrap aluminium and lead to the brass scrap before melting, so as to get an alloy that will be a bit more machinable, as the remelting likely boiled a lot of the zinc out, so you need to replace it with either more zinc, or with another metal. Aluminium or lead alloys well with copper, and if you have a few scraps of silver solder toss that in as well.
The brass is machining fine, so I don't think zinc loss is an issue. I'm thinking it's a dross or impurities issue as it obviously got a lot worse when I added the Borax. Thanks for the suggestions. Cheers Rob
With that small mold you could put it on the end of a wire rope and swing it around after pouring; maybe the extra gravity would help with the shrinkage while it cools. I haven't tried that myself and you are of course free to wait until I do!
@@Xynudu That's why I would try it first personally. I like the mold in the lid idea though; what if you left the flux out and left the mold to cool in place?
Maybe try shaking it up with a vibrator while it cools to provide some mobility to the impurities. You might find they will sink or rise to the bottom or top if they have a different density than the liquid brass.
Rob, Years ago I got bit big time by a bronze that suffered from surface porosity when cast into a hot investment mold. I had no clue that this could happen. Be careful about the assumptions you are making. This 'stuff' is not always logical. Cheers
Hi Rob, Man I feel kinda of bad for suggesting the Borax for flux. I know it is used when brazing with brass and would have thought it would be good for casting. Now, a flux is supposed to help with flow-ability of the metal but looks like it does nothing to degas it. Sorry mate for pushing you in the wrong direction. Thanks for sharing though! Joe
Such is life Joe. It was worth a shot, but I wasn't surprised at the result. I will make up a better skimmer and see if that helps get out the impurities. I will crack it eventually. Cheers Rob
For what it's worth Myfordboy uses flux when casting brass. Theres not a lot out there on the subject and even less that includes machining of the finished casting. Keep at it Rob , production of machine quality brass from scrap is a real money saver .
If you're trying to get your process down, you should be trying one change at a time, Rob. If you can't get all the dross out, you might need to use filters, but that' gonna push your cost up.
I gotta agree with you there Shawn. There's so much misinformation on the web. It's hard to find reliable techniques that work. I will revert back to high temperature and a slow cool down as that looked to work well on a channel called Clickspring. Every time I try flux it bombs badly, despite all the people suggesting it. Makes me wonder if they have ever done any casting. Cheers Rob
Hi Rob. The only way to refine a process is by experimentation. You are bound to get a few less than successful results along the way and all it's cost you is a little gas. I do like the idea of suspending the mold in the vent, that's got to help. Cheers, Alan.
Hi Alan. I totally agree. I'm a bit surprised at the lack of information on the net about this. I suppose not a lot of people melt brass. It's a good time waster anyway. He He. No harm in failing. It's how I learn ;) Cheers Rob
Hi Rob, if I compare your procedure with the instructions on the German website, then you are doing everything right. The only difference is that a graphite crucible should be used. And then only for brass and nothing else. But I'm sure you're on the right track and in the end it will fit. Greetings Michael
Odd result, thanks for sharing. I intend to try when mine is working. Borax if added at the start, makes a glassy layer sitting on top, which should collect and scrape off with the dross. Im suprised it has caused the porosity. Any plans to try copper or alumium bronze? Looks like you easily have enough heat for it.
Hi Rob. When is Borax not Borax. When it is a cleaning product (Disodium Tetraborate Decahydrate). 'Borax' has become a commercial branding and may not have a relationship to the traditional use of "Borax". I notice to have the cleaning product in the background. You may need to source 'Boric Acid' from the Leadlighting crowd who use it as a flux in their soldering. There is a supplier in Queensland who may be able to supply.
Hi Anna. Interesting. Thanks for the heads up. I will look into that (read the packet). Yes, that was the stuff I used. I have some borax based brazing flux that should be the real deal and may try that some time. From the results I have gotten it seems unnecessary as there is considerable powedery dross on top of the melt (totally different to other dross). Cheers Rob
@@Xynudu Another thought - re the deterioration of the furnace liner. The turbulence of the flame seems the accelerate the deterioration. Have you considered using a Stainless Steel liner for the furnace ie rangehood ducting or similar. The melting point of a good Stainless (1510c) is a good deal higher than the metals you are melting and the solid barrier may protect the lining from the turbulence. This is not something I have personally done, however its an idea.
Hi Anna. It's do-able. I have thought about it. The liner needs to be SS as a mild steel liner will definitely not last (I had one in a smaller furnace once). BTW I had a close look at the Borax I unsuccessfully used in the brass melt and it is 99.999% actual Borax. So no point in revisiting that ;) Cheers Rob
Interesting experiment - the pitting, was it the borax or something else? It looks like granules of something, but I'd be surprised if its borax since borax melts at 743o C so it should melt long before the brass melts (900o - 940oC). Perhaps some salts were formed with higher melting point, perhaps the borax attacked the cast iron? Did the clutch cylinder look pitted after that pour? Just some ill informed guesses Rob.
Hi Benny. The cast iron looks OK. The dross is a real nuisance to remove so I might make a better skimmer out of some fly wire or some such. I don't think it's a gassing issue as the voids are not round. It looks more like impurities. The fact that it got a lot worse after adding the Borax points in that direction. Maybe it's reacting with some oxide or some such. I will work it out. Cheers Rob
I've never had any success with flux in my melts (aluminium) and it's all about the temperature (keep it low to prevent gassing). With brass I might go hotter next time, as the temperature was down on this pour. Cheers Rob
@@Xynudu You have not thought about talking to a metallurgist have you Rob--might be worth a thought or two..It would be excellent if you could nail it..
Thanks for that. Hard to be sure, but certainly none seen. He looks to have the melt at a higher temperature. Good video and nice machining. Cheers Rob
