KITH Preparation Class - Heat Treating

[racjarrett88]

Cant have much less than last sunday

[piggy]

I have two questions I will do them is separate post.

1st: blade geometry is a problem maybe partly because of my being a grrrriiil. We got home ed while guys got shop. I have a lot of tools for measuring and don't know how to use any of them. I was a tile setter so this is an old problem for me.

If a blade is 1" wide 1/8" thick and u want an approx. 20`, 10` ea. side doesn't the pre-given measurements more nor less determine the degree on a flat grind? Given that we plan to make sharp knives.

[piggy]

2nd: My forge, Is it better to have forced air on a small forge? I see instructions that don't use any air.

Do I need an opening in the back or top of forge to work as a chimney?

Should I have an optional hole or door on back of forge for larger knives?

Can I just have the hole for the gas? Where is the best place to locate hole for gas? I mostly see them angled upwards from the bottom/side, not in the middle of the bottom. I also see a lot w/ the hole more towards the top on the side.

I have MAPP and propane what is best w/ 1084

Light forge w/ cigar (Ray method) or use ignition on gas bottle?

Is that enough questions to finish my forge?

[racjarrett88]

20 degree angle is for the edge I believe not the primary Hegel the primary Hegel is much shallower around 3 thru 5 degrees I think but I might be wrong

Austin

[racjarrett88]

Bevel not Hegel dang autocorrect

[Ray Rogers]

Lee,

1. Yes, the width of the blade and the thickness of the blade stock do determine the angle of a full flat grind. But, you get to choose what thickness you want to use for your blade and in that way you influence the geometry of the blade. The rest if the geometry is as Austin was trying to suggest: the thickness of your edge before you sharpen the blade plus the angle you choose to use when you sharpen (mostly about 20 degrees). There are other edge shapes like convex or hollow ground (the edge, not the primary bevel) but the basic geometry is what I was referring to.

2. The question of forced air vs venturi is not a simple answer. A major part of the consideration is what you have on hand to build with and how much you're willing to spend. Also, is this for heat treating only or will it be used to forge?

In short, most people would probably find a forced air burner simpler to build and set up especially if fabricating this type of stuff is foreign to them. It's easier to get welding temps out of a forced air burner and they are dead simple to tune up since they don't rely on orifice sizes or venturi geometry and they don't care how far above sea level you may be. But, most people will have to spend more money building a forced air burner even though they are simple to build because they use some moderately costly parts like big gate valves and blower motors.

If a venturi design is easy to build there's a good chance that it will serve well enough for heat treating but probably be only marginal for welding or forging. Venturi burners can get to higher temps but building one that will takes some skill and understanding of how they work. Their working characteristics will change a little bit according to the weather too if a high or low pressure system moves in. You can buy ready made burners that will work well but they will approach the price of a forced air burner which, in my opinion, is the better deal as long as you don't plan to use your forge in any place where electricity is not available. Forced air needs power, venturi doesn't.

MAPP gas alone won't get the job done. I made it work on my mini-forge by drilling out the tip of the torch so more gas would flow and then I added forced air to it. After that, the torch was useless for normal torch work but worked quite well for the mini-forge. If you built a forge in a Campbell's soup can an ordinary MAPP torch would be more than enough but when the forge is big enough to be useful for normal knives you need a much bigger heat source.

DO NOT use an electric or piezo lighter on a forge. There is a term we apply to this design: BOMB. It's not completely impossible to make an igniter work but most people wouldn't set it up correctly and there is no room for error. Don't do it.

If the forge is small enough for one burner, the burner tube should probably enter the forge body near the top center and at an angle that directs the flame across the roof of the forge causing it to curl around the rounded side opposite. The burner should never be pointed directly at your blade unless you want to burn a hole in it. You need a tube to get the gasses inside the forge body and shape the flame, a hole won't do it ( at least not with a wool lining).

Forges don't use chimneys. You need at least one opening to allow you to place your blade into the forge. The burning gasses will exit that same door. If your forge is small you might want a rear door also so that long blades can stick out but this is mostly useful when forging and not so much for HTing.....

[piggy]

OK, I think I am clear on the blade geometry at least for flat grinds. About how far up the blade should the edge bevel go? As it applies to this particular knife. I want to make sure I don't go to far up.

I had my forge design before I seen the tut on the mini forge. I am using a juice can the size like v-8 used to come in. It is longer then a coffee can but skinnier. I don't see me forging a knife anytime soon if ever. So this is for HTing until I get an oven.

I used the word hole but I did intend to use an iron not galvanized pipe. I don't have local access to any refractory type material or bricks. If need be I will use a mix of 50-50 sand and plaster paris then re-do it when I get supplies.

I was told that the nozzle on the gas needs to have the vent holes close to the edge and not further down the neck. Then to insert the nozzle barely into the the tube opening. I am going to use the dimensions on the mini forge tut.

I have an old Coleman pump from an air mattress I plan to use. I have some vent motors and other usable stuff but I think it is over kill for this size.

I did handyman repairs for over 10 yrs I can do just about any house repair even build a house w/ the exception of cement. I know enough about cement to know I don't know enough. It is a lot like metal. My point is that I have a lot of crap, electrical, plumbing stuff that I don't need to buy a lot of anything to build a forge or grinder. I don't think I have given out much back ground I can be pretty handy, I own and can operate a lot of power tools. However, I have no formal training. So I am going to ask a lot of tech questions that might make me sound like I am lost.

I might not make the 15th deadline but w/ all the help I have been getting I think very soon I am going to crank out something that will actually look like a knife.

[Ray Rogers]

I'm not sure plaster of Paris and sand is a good idea. There are formulations for home made refractory on the internet but I don't think refractory of any kind is a good idea on a forge as small as you plan to make. The problem is refractory has a lot of mass and that takes a lot of heat just to get the forge ready to do any HTing and it sounds like you're planning on a small burner. You would be much better off with a wool liner. Inswool is pretty cheap, last I looked $15 plus shipping would get you 2 square feet which is enough for several forges of your size. I've got about half a box of it just laying around, email me your shipping address and I'll send you some ...

[GHEzell]

Originally Posted by Ray Rogers

I'm not sure plaster of Paris and sand is a good idea. There are formulations for home made refractory on the internet but I don't think refractory of any kind is a good idea on a forge as small as you plan to make. The problem is refractory has a lot of mass and that takes a lot of heat just to get the forge ready to do any HTing and it sounds like you're planning on a small burner. You would be much better off with a wool liner. Inswool is pretty cheap, last I looked $15 plus shipping would get you 2 square feet which is enough for several forges of your size. I've got about half a box of it just laying around, email me your shipping address and I'll send you some ...

That said, you will want to coat the inswool with refractory, unless you like breathing silicon-based fibers into your lungs....!

[Doug Lester]

There are others, but High Temperature Tools and Refractory has the Inswool ceramic matting and the refractory cement that you will need to make a coating over it. I like that much better than a mortar, like Satinite for coating the matting. All you need is the a 5# bad and that can be shipped in a flat rate mailer. That's enough to coat the Inswool with in a can forge and have plenty left over for patching. I think that you can probably get enough of the matting in another mailer and maybe both in the largest. All you want is a 3/8-1/2" shell over the Inswool.

Doug

[piggy]

I decided that I can't use any alternative coating or anything else.

This is about checking to see if our regular way of HTing is working. If I use something that is only temporary it defeats the purpose.

I need to slow down take a deep breath and regroup.

What I would like to do is test 2 knives one done on the mini forge and one w/ a 1 brick. They are very popular and much cheaper to make. Some day I think I will buy a HT oven but I don't foresee me using a large forge.

[Naboyle]

Piggy I said the same thing about a big forge... Until I made 2 of them!
You said you don't wanna enter the kith with something that's temporary, why can't it be permanent if it works? Take every bit of Ray and Doug's advice, stick it under your arm and run with it. These guys know what works and what doesn't. They've helped me out more than they'd ever imagine. If it weren't for them I'd still be beating on old files heated in a charcoal cast iron skillet, on a piece of flat railroad track.

[ericbrinkerhoff]

I would like to submit two blades as well .One with my sketchy "pizza oven" temper , and one with my (equally sketchy , no doubt) "torch temper". Or is that too many variables?Or too much crap from the back of the room? Also my knives are going to be the least correct as far as adherence to the original pattern . I didnt stray from the outlines on purpose , its just that sometimes I end up letting the grinder do the talking.

[piggy]

Originally Posted by Naboyle

Piggy I said the same thing about a big forge... Until I made 2 of them!
You said you don't wanna enter the kith with something that's temporary, why can't it be permanent if it works? Take every bit of Ray and Doug's advice, stick it under your arm and run with it. These guys know what works and what doesn't. They've helped me out more than they'd ever imagine. If it weren't for them I'd still be beating on old files heated in a charcoal cast iron skillet, on a piece of flat railroad track.

Naboyle ur right. I've learned a lot here too.

I don't think a mini forge has to be temporary at all. The volume of knives and or size of the knife should dictate the forge size. Why heat up a big space for one knife? What I meant was things like plaster of paris. But your still right. I don't know that this won't work, I do know that K-wool and coating does work. I need to pick one!

How's everyone else coming along? Anyone going to post pics?

[Ray Rogers]

Eric,

Send as many blades as you want, just be sure to mark them so that you know what you did to each one....