some questions please

[volta]

After years of thought and consideration, I've decided to make a serious personal effort in the world of knife making. since this is my first post here I'll give a little background. I'm 19, and a mechanical engineering major. along with other artful and technical things; knives have been a large part of my interests. now that i have the financial means, inspiration, and resolve to try a serious hand at it, i want to make knives and have a couple topics in question.

my first subject in question is forge construction. i really only need the forge to be useful for heat treating, and possibly forging blades no larger than 12 inches. because of this, a compressed air tank or 5 gallon paint can forge seems entirely inefficient. instead i have selected a relatively small forge body to build from. the vessel i selected is a section of some sort of industrial sised, flange ended pipe nipple i spent a lot of effort sifting through a construction site dumpster to get(it is damaged on the sealing faces). internal dimensions are 8" in diameter and 13" long. the sise is perfect. however i am unsure about a couple things.
first, i read on the zoller forge website that you need one 3/4 inch sidearm burner per 350cubic inches, does that refer to the sise of the forge body without insulation, or the inner dimensions of the insulated vessel?
second, my forge body is around 360ci without insulation and only 160ci with 2 inches of insulation. if i am in fact only going to be heating a 160ci forge, do i really need a 3/4" burner? i think a 1/2 inch burner might even be over kill. i haven't seen any 3/8" burners made as of yet but my question is: should i stick to the known 1/2 inch burner and turn the regulator down, or try to build a 3/8". my goal is temperature control so which do you think could be most precise for heat treating.

my other subject in question is steel choice. i have read all of the posts from kevin and think i have a somewhat serviceable, yet extremely basic understanding of steels. with this said, i have narrowed my choice to 1084 and 5160. whichever i pick, i will be using for a long time. for clear reasons, 1084 is a good choice for beginners. 5160 seems a little less recommended and i want to know why. essentially, within my parameters, can one steel make a markedly better blade compared to the other? it is my understanding that 1084 might have better edge holding capability. can 5160 match that capability and also carry better corrosion resistance and toughness? is 5160 a more worthwhile steel to use in the long run? perhaps i am over analyzing this. what are your thoughts? i have no idea why i am attracted to 5160.

in conclusion, i'm mostly just excited to finally be building a forge, and begin. thanks for any advice in advance,
Volta

 

[Stacy E. Apelt - Bladesmith]

Welcome to the BF. Filling out your profile will help. The stickies have good info on forge building, BTW.

Either steel will make a good knife, and one won't perform any better than the other. Once made and finished, I doubt you could tell which was which. The ease of HT is the difference. 1084 is the simplest, and I would suggest you get some of Aldo's 1084FG.

The forge volume is the area you are heating...which is the insulated volume. A 3/4" burner is the minimum. Burners can be too small, but too big is seldom a problem.

As a ME student, you might want to read the sticky on PID control and forges. It has some good info.

Your 8X13" forge is a good size, and will serve you well. Adding a PID will make it really useful. The choice of a blown burner vs a venturi is up to you at this stage, but I would also suggest you consider a blown burner. They can be dialed down much lower than a venturi. In a small forge ,a venturi may be hard to keep down at HT temps. You can always change the burner later if you decide to go with a venturi for now.

 

[Salem Straub]

Hi Volta, +1 to the above first of all. I have made a forge just about that size before, and used a Ron Reil style basic venturi burner in 3/4" size. It was for a friend, and at first he had trouble keeping it below a welding heat. With some burner tuning, we were able to get it to hold a stable flame at 1 psi. to get a nice low heat. My venturi forge will do this as well. The sidearm burner is a good design and easy to build, I've gotten the burner kit from Zoeller before and it works great. If you have a good regulator and the jet is concentric with the burner tube, it should be highly adjustable in terms of gas input pressure and flame size.

One thing that helps is cutting through the wool carefully when installing the burner tubes, and whether or not you are using flares (they help) make the inside of the opening where it enters the insulated chamber nice and smooth and round with your satanite or ITC-100. It holds a flame better that way.

Stacy's right, if you hate the venturi you can just retrofit the burner head to accept a blower.