Hot Spots

Jammer Six

Well-Known Member
I've read that some folks don't like some forges because they create hot spots.

Okay.

So tell me this: don't all forges create hot spots?

What are the bad things about hot spots? (I've looked at the forge I use the most, and I think it has a hot spot or two, but I usually move the metal around when it's heating when I'm heating and beating, so I'm not really sure.)

And how could a forge not create a hot spot or two?
 

EdCaffreyMS

"The Montana Bladesmith"
So tell me this: don't all forges create hot spots?
The short answer is yes, however, it's a matter of degrees, literally. In general forges of a square or rectangle design, suffer the most from "hot spots". This is because the burner(s) cannot help but be directed into the forge at 90 degree angles, greatly increasing the problem of hot/cold areas (spots). There is a tremendous difference in the size and intensity of the hot/cold spots within a circular forge versus a square or rectangular design. With careful consideration of burner placement/angle, hot/cold spots can effectively be eliminated within a circular designed forge.

What are the bad things about hot spots?
When it comes to forging "straight" steels, intense "hot spots" can create havoc with heat sensitive steels such as 52100. This particular steel is very heat sensitive during the forging process. It will give you no outward indicators that it's been "over heated"....until you finish a blade... then it will cut no better then a piece of sharpened mild steel. I've had and seen various forged 52100 blades that would either simple be terrible cutters, or worse, have portions of the finished blade that would cut as I would expect 52100 to, and other portions of the blade that were terrible. Experience has taught me that usually a blade with "good" and "bad" portions was usually forged in a multiple burner forge of square/rectangular design. With other steels, there are a number of detrimental consequences that can occur because of hot/cold spots, which manifest themselves in various ways..... an example of this are blades that warp badly in the quench....most don't realize it, but this is often a result of uneven heat during the forging process and/or the uneven heating prior to quenching, or attempting to conduct various thermal cycling procedures with a forge that exhibits excessive hot/cold spots.

Usually by the time an individual is ready to delve into making damascus (laminated steel), they have discovered/learned how badly hot/cold spots can effect things, but there are those who are impatient, and dive into it before they are ready, with a forge that is ill suited. The results are generally catastrophic in failed welds, warped or cracked blades, etc.

And how could a forge not create a hot spot or two?
It's all in the design of the forge. There's a reason that most seasoned Bladesmiths build/choose to use a forge that is of a circular design, with a single burner. These types/designs create the least amount of "hot spots", and with careful consideration of burner placement, hot spots can be minimized, if not eliminated. The main reason you see most forges that are offered for sale being of a square/rectangular design, is because that particular design is easy/cheap to build. The consideration of how effective or ineffective the forge works is rarely a consideration.

When I designed/built this welding forge, the elimination of hot spots was foremost on my mind: http://knifedogs.com/showthread.php?43590-New-Welding-Forge-WIP
I managed to accomplish the goal. Although this forge is large/heavy, and it takes an hour or more to reach/level out to welding temp, there are no "hot spots" within the area that billets can be introduced. (there's always a level of "give-n-take" when it comes to forges.... it's up to the individual to decide what aspects are most important/desirable, and what aspects (on the down side) are acceptable.....and then decide the best way to gain those aspects they most desire, while minimizing those aspects they do not want.)
 

EdCaffreyMS

"The Montana Bladesmith"
Page 3 of the thread has one pic of it running, along with a couple of readings off the pyrometer.
 

Jammer Six

Well-Known Member
Okay, next question.

I don't own forging equipment. Rather, before I buy anything, I'm taking a series of classes from a place that recognized among artists here in Seattle: pratt.org.

Pratt is dedicated to all artists, not just blacksmiths, but they teach a fairly complete blacksmithing curriculum, and I like the people there.

Under this arrangement, however, I have no control over the equipment I use. (That's not a problem at my skill level, with my level of knowledge, it's probably a good thing.) So how would I tell if the the forges they have me using have hot spots?

(I wouldn't say anything, of course. If I were them, I wouldn't be interested in my opinion until I actually know something about blacksmithing. But I'd watch. Knowing if the forger has hot spots, I'd watch to see what they do, when they do it, how they do it, where they do it and how often.)
 

EdCaffreyMS

"The Montana Bladesmith"
So how would I tell if the the forges they have me using have hot spots?
Visually, it's obvious....you will see areas inside the forge (gas type forges) that are brighter then other areas. Typically, a gas forge of square or rectangular design will have the burner(s) entering the forge at either the centerline of the top, or the centerline of one side or the other..... either will direct the flame at the opposite interior wall. Common thinking is that where the flame is directed at will be the hottest location.....it's actually the opposite, where the flame is directed will be a "cold spot" with the area surrounding it being hotter.

I'm familiar with Pratt, and here's a caveat... in general blacksmithing work, where "mild" steel is primarily used (which is what the classes at Pratt teach), hot and cold spots in a forge do not have the same impact as they do when working with "knife" steels. If these classes you are attending are designated as "Blacksmithing courses" (which they are), you will likely learn very little about hot and cold spots in a forge, or about heat treating. That's not any kind of "knock" on ornamental Blacksmithing, it's simply a fact that since "mild" steel is the primary media used, knowledge of those things is simply not important as they are when forging "knife" steels. I came from a background in Farrier work and ornamental Blacksmithing, where the general idea was to heat the metal as hot as possible, in order to get as much work done per heat as possible. It wasn't until I became a Bladesmith, that I learned/understood how little I knew about heat treatment, and also the importance of forging high carbon/alloy steels at the correct temps. Later, as I got into making Damascus, the importance of those hot and cold spots in forges became quickly evident. Long story short, those type of classes are nice to familiarize yourself with tools and techniques, but unless you learn from an actual Bladesmith, using carbon and alloy steels, it will be a totally different ballgame when you step up to a forge on your own, with "knife" steels.
 

Jammer Six

Well-Known Member
Thanks.

One of the ladies teaches a Damascus class at Pratt, and apparently they have some kind of custom press built for Damascus.

One of my aims there is to build myself a set of Damascus wood chisels, (like every other woodworker I know, I've never owned a complete set of chisels) so I'm hoping at least she knows something about heat.

Going from where I am to knowing how to heat and beat mild steel would be a large improvement! :D
 

EdCaffreyMS

"The Montana Bladesmith"
Now that I understand you are just starting out, I would recommend not to get too concerned about "hot spots" in a forge. Right now just concentrate on getting your feet wet, and learning the basics of the tools, and how to manipulate steel. As you gain experience with the basics, and as you move forward with "knife" steels, the importance will make itself evident.

I know it's exciting to think about building damascus chisels, but I generally advise folks to work with "straight" steels and learn about them before diving into damascus. In your case, you'll have guidance standing right beside you, but I feel its very important to have a given level of experience forging straight steels before diving into damascus....it's not that it can't be done, but some experience with straight steels will help you understand and solve the issue that will arise when learning how to create damascus.

All that being said, it's just my opinion. We all learn at differ rates, and in different ways, and when it comes to forging steel, each time we step up to the forge, it's a learning experience. Go for it, and have fun!
 

Jammer Six

Well-Known Member
Yup, just starting out. I've spent exactly two and a half hours at the forge at Pratt. I followed directions and made a thingy that was supposed to be a heart, but mine looks sort of like chopped liver. My wife's looks a lot better than mine does. So far, we've established that blacksmithing is, by a long, long shot, harder than it looks.

(The upside is that my wife loved it. She had been watching Forged In Fire, and I took her to Couples Forging Night as a surprise.)
 
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Jammer Six

Well-Known Member
In your case, you'll have guidance standing right beside you, but I feel its very important to have a given level of experience forging straight steels before diving into damascus....it's not that it can't be done, but some experience with straight steels will help you understand and solve the issue that will arise when learning how to create damascus.
I've said exactly the same thing to students in other sports: diving, sailing and shooting. "The more experience you bring the class, the more you'll get out of the class."

On the other hand, all those sequences have also convinced me that the fastest way to go from zero knowledge to some knowledge is to pay an expert to stand beside you and teach you. The internet is great for book knowledge and factoids, but there's no substitute for the expert standing beside you telling you how to change the angle and force of your strike as you do it.
 

Kevin Zito

KNIFE MAKER
I've said exactly the same thing to students in other sports: diving, sailing and shooting. "The more experience you bring the class, the more you'll get out of the class."

On the other hand, all those sequences have also convinced me that the fastest way to go from zero knowledge to some knowledge is to pay an expert to stand beside you and teach you. The internet is great for book knowledge and factoids, but there's no substitute for the expert standing beside you telling you how to change the angle and force of your strike as you do it.
You taught shooting?


Sent from my iPhone using Tapatalk
 

Jammer Six

Well-Known Member
Handgun, Defensive Handgun. Never taught any long gun, there are a lot of people a lot more qualified than I am on long guns. (That's actually true for just about anything, though.)
 
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