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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #1  
Old 02-27-2012, 01:36 AM
Edy420 Edy420 is offline
 
Join Date: Feb 2012
Location: New Zealand
Posts: 7
Can I use concrete to make a gas forge?

Hi guys, my first post on the forums, woot.

First off I'm extremely impressed with what I've seen on the forum so far, I hope to become a long term member

My first project was a machete I was making from an old chainsaw bar, which after much investigating I have discovered it wouldn't be any good because its made from an alloy.
I discovered that after 4 hours of grinding :P but I'm a firm believer in learning the hard way, so all is not lost.
I figured I'd need to soften the bar so I could grind it much easier and began making a knife forge from a design I found on youtube.

Its basically an old L.P.G tank with the top cut off for a lid and materials including refractory and insulating kao wool.
But I can not source the ceramic kao wool (or porcelain, I forget :P ) here in New Zealand.
I've done all the cutting I need to do, next up is the welding etc and I even have pre made refractory all on standby, which leads me to my main question.
Will concrete work as the insulator instead of kao wool?

It doesn't have to last long as I am in the process of moving over seas, where I plan on doing everything properly, but I wanna get my hands dirty now!

Thanks in advance.
On a side note I made a charcoal forge out of a frying pan and a paint can, with a vacuum for the air input, but its only good for little knives and multiple failed projects
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  #2  
Old 02-27-2012, 08:55 AM
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Ray Rogers Ray Rogers is offline
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Concrete is a big NO! Concrete will contain trapped water and will explode when it gets hot enough. But, you said you have refractory on hand - if you have refractory cement then just use that. However, New Zealand isn't a tropical place, seems to me there should be a source for some type of ceramic wool there. Check with any stores that sell wood stoves or large industrial gas heaters. Inswool or kaowool is nothing but the insulation they use in heating systems. If you can get that material, all you need for a forge body is that wool plus a steel form to hold it - no cement is needed for short term use.

BTW, a chainsaw bar can be decent blade steel, the trick is to know which bars are good and which are crap. Until you can be sure, stick with commercially available blade steel and your results will be much more rewarding ...


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  #3  
Old 02-27-2012, 07:25 PM
Edy420 Edy420 is offline
 
Join Date: Feb 2012
Location: New Zealand
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Thanks for the tips Ray.

I'll definitely keep on the lookout for some inswool.
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  #4  
Old 02-27-2012, 07:28 PM
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SBuzek SBuzek is offline
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also check to see if there are any pottery supply places aroun d you,they will usually have it.
stan


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Old 02-28-2012, 06:58 AM
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Crex Crex is offline
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If you can get any quantity of soft fire brick, used is ok, crumble it up into smaller fragments - BB to marble size - and mix with the mortar refractory for a lighter forge. Or if you have access to enough soft firebrick just cut and shape to form the liner in your forge.
Not correcting Ray, just adding that he is talking about boiler and furnace insulation not household insulation - high temp stuff.
THink things through and be safe, gas forges can be dangerous and deadly if not treated with respect and common sense. Don't rush past safety.


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  #6  
Old 02-28-2012, 09:16 AM
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Ray Rogers Ray Rogers is offline
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Thanks Crex, that's a clever idea which I'll add to my list. Edy420, the wall thickness does not have to be massive, usually better if it isn't. Line a steel form like a piece of stove pipe with an inch or a bit less of Crex's mixture and you'd have plenty of insulation. If you can work a layer of chicken wire into the middle of it that will help keep it from cracking up and falling apart after it's been heated a few times. Forges always need their interiors repaired regularly no matter what you make them out of ....


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Old 02-02-2013, 10:23 AM
RiverLefebvre RiverLefebvre is offline
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Question I have a similar issue.

I managed to find a DIY forge plan from an old newspaper from the 40s. So in this plan it involves a double cast iron sink to use as a forge/reservoir. I immediately got to work and my brothers friend pointed us to a man claiming to have a double sink (cast iron) he wanted to get rid of. Upon our arrival we saw the sink and it was gorgious.... One problem.. It appears to be made from concrete... Now what i really want to know is, if i were to line the inner sink with clay, would that prevent it from exploding from moisture? I had to get this 400lb sink out of his basement and i would love to know if i can actually do something with it. So the basic question is, Is concrete safe to use if it is coated in clay?

Thanks, i would have started a new discussion but i'm brand new to the site and not really sure how... Love the discussions by the way, they are very informative!


-River
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  #8  
Old 02-02-2013, 12:50 PM
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Ray Rogers Ray Rogers is offline
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I'd have to err on the side of caution here and say don't try that. I'm not familiar with the construction of those old sinks but whenever a forge is running the heat eventually reaches the outer skin. If enough heat gets to the cement there could be a problem.

Anyway, there are a lot of better ways to build forges these days than using an old sink. Maybe the sink would be dangerous, maybe not, but you'd still have a 400 pound heat sink and that's not good. Build yourself a simple forge that can be run safely and efficiently using modern materials...


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Old 02-02-2013, 01:57 PM
RiverLefebvre RiverLefebvre is offline
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Thanks

Not sure what ill do with the sink, maybe keep it for a reservoir... But i will do more research on modern approaches...


Thank you for the very fast response! Now i will not have a concrete all over my yard! haha




Thanks,
River
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