oxygen/acetylene tip preference for melting precious metals

[didit]

For those of you who use oxygen/acetylene to melt your gold/sliver/etc...

do you have any preference as to what type of tip to use on the torch, such as a cutting tip, brazing tip, or heating tip?

I was planning on using a cutting tip on my oxygen/acetylene torch to melt gold and silver since I am accustom to the cutting torch.

I have access to several brazing torch tips and also a heating torch tip that I could use but I do not have experience with brazing so have never used one.

I am sure there is a difference in the amount of heat produced and oxygen/acetylene used by each but as I said I am not familiar with brazing. I think the brazing tip does not burn as hot but still high enough to meet the melting point for gold and silver.

Does anyone care to share if they have preference and why?

Thanks.

 

[adam mizer]

When I got small rosebud tip I was pretty happy.
Big rosebud used to much fuel for me.
Then I found small rosebud. Works very reasonable.
It depends on how much you are melting. 00-4 depends on how much material to melt. Rosebud my favorite.
I use small mini torch set now to conserve fuel, works good for my purpose. Some shot, contact points small to large etc.

 

[adam mizer]

When I got small rosebud tip I was pretty happy.
Big rosebud used to much fuel for me.
Then I found small rosebud. Works very reasonable.
It depends on how much you are melting. 00-4 depends on how much material to melt. Rosebud my favorite.
I use small mini torch set now to conserve fuel, works good for my purpose. Some shot, contact points small to large etc.

Cutting setup has larger handle, I like the smaller torch.
However every torch is useable.
If your wondering why my tip is so dirty I melted some metal that took forever at a seriously high temperature.

 

[goldshark]

A small rosebud will throw out some serious heat. Like Adam said, it depends on quantity, and patience. I have both types of torches, but found you can do more faster, with the proper insulation to contain the heat, even with the smaller torch (cutting torch ), or brazing tip.

 

[Shark]

I use a light duty cutting torch. I have a propane cutting tip as well and even prefer it over acetylene for refining. Being light duty it doesn't have the large handle and fine tunes a bit easier than the medium or heavy duty torch's do.

 

[didit]

Thanks for the advise. I have a rosebud tip in a batch of tips I bought at an estate sale and I think I'll try that one out. The smaller the tip the better makes sense economically to me. For reference I only intend to melt small amounts (anywhere from 100g to 200g at a time). I do have a MAPP gas torch but only with the small bottles and while those would suit the purpose they are more costly than oxygen/acetylene for me.

 

[adam mizer]

The Mapp torch would be used to preheat the mold you will be pouring into.
Would give nice pour lines and aide in less oxygen getting to metal surfaces as it cools.
Works good on silver and PMG I've read and watched some videos.
The oxygen will absorb into certain metals and cause troubles with finish if cooled too quickly when poured.
I didn't have problems sharing the flame of the torch on the mold.
Also you want to make sure the mold is dry.

 

[eaglekeeper]

I converted my old Oxy/Acetylene set up to use Oxy/propane.

 

[anachronism]

I think a large cutting tip has too much flow. Personally I use a medium welding tip and can happily melt 200g bars with it without blowing the gold all over the melt area. Which is a concern until it's caked properly.

 

[didit]

I converted my old Oxy/Acetylene set up to use Oxy/propane.

I actually didn't realize one could use an acetylene regulator on a propane tank until now. I do believe I will reconfigure to propane since I have a tank, it's cheaper and more readily available, and it's a much cleaner burn than acetylene. I'll save my acetylene for just cutting instead.

 

[didit]

I think a large cutting tip has too much flow. Personally I use a medium welding tip and can happily melt 200g bars with it without blowing the gold all over the melt area. Which is a concern until it's caked properly.

I agree but am not sure what is too large or too small since I am not familiar with welding with gas (I've only ever done arc). I have several different brazing tips of different sizes, No 1, No 4, No 6, etc. Would a No. 4 be what you would consider medium?

Thanks.

 

[didit]

The Mapp torch would be used to preheat the mold you will be pouring into.
Would give nice pour lines and aide in less oxygen getting to metal surfaces as it cools.
Works good on silver and PMG I've read and watched some videos.
The oxygen will absorb into certain metals and cause troubles with finish if cooled too quickly when poured.
I didn't have problems sharing the flame of the torch on the mold.
Also you want to make sure the mold is dry.

Thanks. I do plan on using the MAPP for heating molds when pouring, I just didn't want to use for melting since I only have small bottles.

 

[snoman701]

A big cutting tip is useful for dirty melts. Use the oxygen jet to oxidize less noble metals into the borax.

I use a rosebud for 90% of my melts though.

 

[anachronism]

I agree but am not sure what is too large or too small since I am not familiar with welding with gas (I've only ever done arc). I have several different brazing tips of different sizes, No 1, No 4, No 6, etc. Would a No. 4 be what you would consider medium?

Thanks.

That's an extremely good point Didit, I shall go check later and let you know.

 

[anachronism]

A big cutting tip is useful for dirty melts. Use the oxygen jet to oxidize less noble metals into the borax.

I use a rosebud for 90% of my melts though.

What's the average size melt Sno? Do you get the penetration you need with larger amounts with a rosebud?

 

[goldshark]

What's the average size melt Sno? Do you get the penetration you need with larger amounts with a rosebud?

A rosebud puts out a lot more BTU's than any other torch tip. Metals will heat via their thermal conductivity, so more BTU's = faster melt. Cutting torch makes it too easy to hit the O lever, possibly blowing powders all over the place. For me, rosebud all the way for smaller pours, Propane furnace for anything over 5 TOzs.

 

[snoman701]

What's the average size melt Sno? Do you get the penetration you need with larger amounts with a rosebud?

Anything over an ounce I do in a number zero crucible inside of some insulating firebricks and heat from the outside. With the rosebud I just drilled a hole in one and sorta set the torch so it aims through the hole.

I've done 5 oz melt with it, but I found that there was a lot of powder in my tray, so I don't like to think about what may have made it out of the tray. I put the melt dish on a firebrick in the middle of a catering tray. I'd love to say that it's clean, but right now it's an absolute mess of piece of flux, etc.

 

[adam mizer]

I actually didn't realize one could use an acetylene regulator on a propane tank until now. I do believe I will reconfigure to propane since I have a tank, it's cheaper and more readily available, and it's a much cleaner burn than acetylene. I'll save my acetylene for just cutting instead.

The hose material for propane is different.
Propane will eat up acetylene hose.

 

[Shark]

Like with refining, if you are going to use propane set it up right. Short term acetylene gauges and hoses will work. The problem is they will fail with little to no warning.

 

[adam mizer]

I found this:

The least you’ll need​

• You WILL need to change your Acetylene Regulator to a Propane type (including for Propylene).
• You WILL need to change your Acetylene Hose to a Propane Hose (including for Propylene).
• You will need to check the label on your Flash Arrestor, if it says “Fuel”, it’s OK to use with Propane & Propylene. If it says “Acetylene” you will need to change it for a “Fuel” type.
• Your Torch SHOULD be OK for Acetylene, Propane or Propylene, ours certainly are, but if in doubt, you should check with the manufacturer. DON’T TAKE RISKS WITH GAS!!!!

The link: https://www.thewelderswarehouse.com/blog/swapping-from-oxy-acetylene-to-oxy-propane-or-propylene/