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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 12-10-2015, 03:52 PM
yogurt yogurt is offline
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Forge questions

Just finished building forge of adequate size for up to big Bowies. All fire brick in steel frame. Didn't need refractory cement but lined anyway.


Have burner coming... http://www.ebay.com/itm/231758543576...%3AMEBIDX%3AIT

So, question. I had planned to install this to the top, pointing down... Any advantage between between top and side mounted burners?

Also, planned on affixing this with refractory caulk. Opines?

Many thanks!

Chris
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  #2  
Old 12-10-2015, 04:51 PM
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Ray Rogers Ray Rogers is offline
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Chris,

First, welcome to the forum!

Now the bad news: that is quite possibly the worst forge design and burner combination imaginable. Sorry, not trying to put down your building talents, I'm talking about the design. Here's why that is so bad for knife making:

It has a square or rectangular interior. That means the gasses can't move without a lot of turbulence and that means uneven heat. Uneven heat means you cannot heat treat a blade correctly.

Then there is the brick itself - massively heavy. That, in and of itself, is not a complete deal killer but it does mean this forge will take a significant amount of time to reach forging temps (if you plan to forge) and that means you burn a lot of gas while the forge heats. A simple thin metal shell and some inswool will run circles around this forge body.

Finally, the burner. I admit I'm not familiar with that particular burner but it is an atmospheric burner and it does show a small tightly focused flame. That should work well enough in a round body forge of small size but I'm guessing it will take most of the rest of your lifetime for it to bring that brick forge to a useful temperature.

That might be a slight exaggeration - I guess you will be able to tell me once the burner arrives and you try it out. But, even if a miracle happens and it does the job wonderfully you still have a big problem. Your choices for mounting the burner are either the top or the side (just as you asked about). From the top, the burner will be pointed directly at your knife and that is a very, very bad thing. From the side, it will be pointed directly at a flat wall which probably means the blade will never, ever reach forging or heat treating temperature.

You have the body built and the burner coming soon so you might as well try it. Who knows, you might find out I have more hot air than your forge does. But, if that forge doesn't work out we have lots of info here about how to build a forge that will work without spending a lot of money ...


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  #3  
Old 12-11-2015, 02:14 AM
yogurt yogurt is offline
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Well, it'll get fire to it Fri or Sat when the burner is supposed to arrive. Mon at latest.
About 4" wide 7.5" and 16" deep. What's your guess as the time it heat up?
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  #4  
Old 12-11-2015, 06:10 AM
jmccustomknives jmccustomknives is offline
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Yeah, I agree with Ray. Those hard firebricks will suck the heat right out of the forge. When I built my forge I use them, backed up by 2 layers of Kaowool. It still take 30 min to reach welding heat. I'm afraid that one never will reach welding temps.
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  #5  
Old 12-11-2015, 07:06 AM
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Let us know how it performs after firing up and running for 15 - 20 minutes, then it'll be easier to ascertain what or if anything needs to be changed.
My experience tells me you're going to run into the problems Ray has pointed out, but you are close enough to fire time to test, before changing anything. That deep and large a chamber will probably need two torches to get up to forging heat with that torch design.
Another issue not mentioned, is that with the design you have - cool down time will be very long. Not a good thing in a closed or semi-closed shop. Can't just shut her down and walk away safely.
Also, that's a mighty big front door. If your torch proves adequate you are still going to have a tremendous amount of heat loss out the front and will probably need extensions on your tong handles.

All that aside....good luck and be careful.


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  #6  
Old 12-11-2015, 07:39 PM
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Will certainly provide info as I get it on how this works!

Also, have a "no touch" infra-red thermometer gun coming that reads to 2440 degrees F. That will help me ensure proper HT temps.

After a couple mid heat cycles on the forge, I'll really heat it up on a piece of scrap steel and see what I'm getting.
Have stock on 440C and 1095 right now... will be adding a few options as I get down the road a bit and will post results and ALWAYS look forward to all your comments/critiques/praise (when appropriate).

Right now tracking shows that the burner could be here tomorrow (Sat), or Monday. I'm getting anxious, want to get cracking on this stuff!

Arizona has a good and very active (I understand) knife makers (collectors) association that a couple guys have invited me to. I'll need all the help I can get! Though I have extensive history in welding and tool making, the knife biz is new to me other than material removal on springs etc. I DO plan on getting into this full time in my retirement (NOW- HA) and even building a tire-auto hammer or a three pulley eccentric hammer (helve hammer I think it's called)

All for now and ALWAYS, thanks for any input you guys have!

Oh!, and here's my first one! I know I did not reach 1925 F (more like 1800F) so it's on the soft side. 440C.


Chris

Last edited by yogurt; 12-11-2015 at 07:42 PM.
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  #7  
Old 12-11-2015, 07:44 PM
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Here's where I got the forge concept

https://www.youtube.com/watch?v=-CTHR6GKg2Q
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  #8  
Old 12-11-2015, 08:00 PM
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Ray Rogers Ray Rogers is offline
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Just so you understand why that knife is soft it is because you can't heat treat stainless steel in a forge. Not correctly anyway. It isn't enough to simply hit 1925 or whatever else may be required, you also have to be able to hold that temperature precisely for and extended length of time. That's never less than 20 minutes and for some steels maybe as long as an hour. That just isn't likely to happen in a forge, at least not the kind most of us build. The result of trying is going to be a much less than optimal crystalline structure in the steel. The blade might work well enough to convince you that the heat treatment worked up until the time you get to compare it to a properly treated blade of the same steel.

The thermometer might help with carbon blades but only if you expand your concept of proper heat. Even for carbon steel simply hitting the temperature is not enough. You need to know the moment the target temp is hit and then get the blade into the quench before it has time to heat more than about 100 degrees beyond that point. And that's just for the simplest carbon steels. Alloyed steels like O1 also require soak times at specific temps, although for periods shorter that stainless, to get the best results from them. To be honest, O1 will make a serviceable blade if you just wave it over a match (almost) but the difference in the results between a half baked heat treatment and one that is done correctly can be enormous ...


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Old 12-12-2015, 02:02 AM
Doug Lester Doug Lester is offline
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I would not recommend either 440C or 1095 for heat treating in a forge. The problem with 440C is as Ray explained above. The 1095 has problems due to being high carbon steel that's above 0.85% carbon. Steels with that much carbon need a soak of 5-10 minutes at about 1450-1475?. You might be able to do it in a gas forge if you're lucky but you probably will overheat the steel and put too much carbon into solution in the austenite. That can give you a problem with retained austenite that will have to be corrected later. If you stick with a steel that starts out around 0.84% carbon you can put all the carbon into solution in the austenite and not have a problem. The same with a hypoeuticoid steel that has less than about 0.75% carbon, something like 5160. You can heat them up to just a little over non-magnetic, hold a half minute and quench.

Yes, there are ways to deal with retained austenite after quenching but it's best to avoid it.

Doug


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Old 12-12-2015, 05:33 AM
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Nothing to add to what Ray and Doug have to say. These are the things all of us have to learn - eventually through trial and error - or up front like you have the opportunity to do at this juncture. The "Net" is a wonderful tool and info source, but also provides us with a lot of not so good and just plain bad info as well. You're in good hands here if you take the time to read and understand.
Do not get discouraged, this is a very challenging and rewarding art form to get right. Just got to do it.

By all means accept the association invite. There always seem to be a lot of makers in the collector groups I have known. If not, they will definitely be able to put you in touch with some of the local makers. Those kind of connections are tremendously helpful toward your learning curve. You will find, as here, most makers are very forthwith on information and direction.

You will most likely have problems getting accurate readings with the IR T-meter in your forge as it is designed due to hot/cold spots that will exist even in the steel you are cooking. It will help you understand what is basically going on in your forge in general, but that's about it.


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  #11  
Old 12-12-2015, 05:44 PM
yogurt yogurt is offline
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All great info guys! You will never get a lack of appreciation from me, that's for sure!
I know I have a great deal of learning and experimenting to do... and it'll take some time,
but I'm in it for the long run! This will be a retirement biz for me. Gathering info, tools and
equipment now and learning on the run.

More as it comes!
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  #12  
Old 12-12-2015, 05:48 PM
yogurt yogurt is offline
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OH, another thought of the forge. Aside from being able to block of the front (no problem) it
was mentioned that it's just to tall. Could easily put fire bricks in the bottom to take up space (40%?)
but will that just add to the already large thermal mass I have going?

I'll get my burner and test... see what I've got. That'll tell me what I need. Re-design, scrap it, start over,
get by or what.
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Old 12-12-2015, 06:29 PM
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Ray Rogers Ray Rogers is offline
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'Too tall' might just be the perspective of your photo. Somewhere up there you said what the interior size was but I don't see it right now, at the time it didn't seem all that large to me. Be that as it may, all those bricks could easily be a deal killer and adding more isn't likely to improve the situation (as you already realized). Part of the answer depends on what you plan to do with the forge. As I said earlier, heat treating and/or forging could turn out to be problematic. But, if your forging sessions tend to run many hours long and then you want to anneal the work you have done having all that mass can be an asset. For most of us retired types forging all day is a thing of the past in which case a redesign is likely to be in your future ...


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Old 12-12-2015, 08:57 PM
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Naboyle Naboyle is offline
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I'd suggest buying Ray's forge building DVD. From the feedback I've seen its awesome and will have you up and running in no time. If he had made it a few years ago I wouldn't have 2 forges sitting in the corner ready for the scrap pile!
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Old 12-14-2015, 06:57 PM
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Ok... Burner arrived today. Got it set up through a brick close to the back. At first light, it was pulsing badly and sometimes the flame would jump up to the air holes. Looked at it and the gas orifice was too far up the tube. #3.48 at Ace Hardware got me a F/F connector and a close nipple. Gas orifice is now down the burner tube, in front of the air inlet. Runs good now at 3-8 psi where at first, it would snuff at under 7 psi and never got a good roar.

My cam really sucks so please forgive that. Got the bricks very warm today, had to eat, out to light em up now. Here's some inside views and a little movie from the first real firing.





http://vid1138.photobucket.com/album...e/IMAG0026.mp4


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Last edited by yogurt; 12-14-2015 at 07:02 PM.
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