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First time forging a knife, learned a lot but definitely a bad knife. How can I improve?


William W

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I didn't want to use nice steel, so the blade is one piece with two scraps welded on for the handle/tang.  It's medium carbon steel.  For my anvil I used an old sledge hammer head with a couple of tie in points and secured with a ~50lb logging chain to give it some weight.  The weathers been below freezing for weeks, so I put the whole assembly over a low burning fire which held the "anvil" at about 400f.  The metal started at 3/16, and I forged the primary bevel down to about 7/64, before finishing it in a grinder down to 5/64.  I then packed on charcoal and heated for 3 hours.  Based on the grind test that definitely increased the carbon content but still not as high as is good for a blade. Quenched in motor oil, then tempered it by putting it in a 400f oven for 2h, letting it cool, then putting it back in for another 2h.  I put on the secondary bevel with a bench grinder,  and plan to finish it by just working at a coarse whetstone.  

knife1.jpg

knife2.jpg

knife3.jpg

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What are things that you don't like about it?  What would you change?  Why?

 

Geoff

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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Geoff has good points….. after you have thought about them for a while  make another one….. that is the most important part…. Improving on what you didn’t like about the last one …. 

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depending on what you want to use it for, I would maybe go back to the grinder to thin down the edge, it is looking a bit thick for a general purpose knife?
for carburization it is important to hold the blade at the austhenitic temperature so the carbon can migrate and be absorbed. for mild steel that point should be 800-850 Celsius.

If you go higher than 1000C, that can lead to carbon loss.
time and temperature lead to transformations.

the thinner the steel the faster the transformation occurs but you still need the right temperature.

if you want to generally improve in forging,

make or buy decent tongs!
learn hammer technique

get a good hammer with a properly dressed face

make more tongs

then, study metalurgy

-then throw it out and study japanese forge philosophy

agonize for 5 years until you reach enlightenment
congrats you improved!-
 

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28 minutes ago, J.Leon_Szesny said:

If you go higher than 1000C, that can lead to carbon loss.

This is not accurate.  Pack carburizing is even done in industry up to 1100C.  As long as there is more carbon outside than inside, diffusion will push/pull the carbon in.  If the atmosphere control is bad and you end up burning your carbon away from the steel, then you will start to get decarb.  

 

31 minutes ago, J.Leon_Szesny said:

the thinner the steel the faster the transformation occurs but you still need the right temperature.

I feel it should be noted that thickness does not directly affect the phase transformations, just temperature.  Thickness does factor into how fast the steel gets to the right temperature, though.  

 

 

Since nobody else has mentioned it:  @William W, you need top incorporate a few normalization cycles into your process after carburization.  Soaks that long at those temps are really going to increase grain size, and you need to refine that down.  

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4 hours ago, Jerrod Miller said:

This is not accurate.  Pack carburizing is even done in industry up to 1100C.  As long as there is more carbon outside than inside, diffusion will push/pull the carbon in.  If the atmosphere control is bad and you end up burning your carbon away from the steel, then you will start to get decarb.  

 

I feel it should be noted that thickness does not directly affect the phase transformations, just temperature.  Thickness does factor into how fast the steel gets to the right temperature, though.  

 

 

Since nobody else has mentioned it:  @William W, you need top incorporate a few normalization cycles into your process after carburization.  Soaks that long at those temps are really going to increase grain size, and you need to refine that down.  

Thanks for the comment.  My carburization was around 1000C, buts that's a guess based on fitting the output of my crappy diy usb webcam based spectrometer to Planck's law.  How much does having the whole blade packed effect the carbon diffusion? I lined about the top half inch with charcoal pack, but I'm now wondering how much carbon I lost out the uncovered area.  

For the normalization, I'm about to say things based on some Googling and my memory of material science classes, there is a decent chance this is wrong so let me know.  Grain growth is something that starts right about when you get in to austenite ~700C, but, for our applications, doesn't become much of an issue until around 950C.  So for this situation will the high heat cause much of an issue? My understanding is normalization is done by repeatedly heating the steel well past the austenite transition, then "quenching" it in air.  When doing this is the aim that perfect 10-50nm grain size range, or are we working in the micrometer range just aiming to get as small as possible?

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I was trying to get a dialog started on basic stuff.  The ability to look at your own work and be critical of it ( which is not to say negative, but realistic) is important.  It's hard to do.

 

I see a couple of things that I would like to improve, if this were my work.  I don't like the sway back, it either needs to more pronounced 

Mundial 5 Curved Narrow Semi-Flex Knife | LEM Products

Or less

 

Handmade Grind Hunting High-carbon Steel 1095 Straight Knife 60 Hrc Fixed Blade Outdoor Camping ...

 

The nicks on the various edges are something to worry about, you really want to grind them out.  The fissure at the end of the tang is a problem as well.  The blade seems to have a curve to it.  If it's not hard yet, you should be able to lightly hammer it straight.

 

On the plus side, it exists and you did it.  No one should expect perfection on a first try, but this is much better than most of my early work.

Really look at it, what do you see.  What do you like, what do you hate.  Keep doing the stuff you like, identify the rest and figure out how to not do that the next time.

 

Geoff

 

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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22 minutes ago, Geoff Keyes said:

Really look at it, what do you see.  What do you like, what do you hate.  Keep doing the stuff you like, identify the rest and figure out how to not do that the next time.

Wholeheartedly agree with Geoff!

To add another step: I always encourage people to begin drawing their designs, IN PEN.  Most people will say "but I suck at drawing", but it doesn't matter.  Keep drawing and you will get better, Just like Forging knives!  And don't erase the drawings (thus the reason for pen not pencil), complete the drawing, analyze it again, and draw again.  You'll be surprised how quickly you learn what lines you do and don't like.
I generally like to think what my writing teacher taught holds true for most things: "If you tell me you have a wonderful idea, but just can't quite articulate it, I'll tell you that if you can't articulate it you don't have a wonderful idea: you have a brain full of muddled ideas.  You must straighten them out first for them to become good ideas, and then learn how to weave them properly for them to be wonderful."

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Grain growth starts even before austenitic (and austenitic is typically closer to 800C, but varies quite a bit by alloy), and is always a thing to be concerned with.  You generally want to reduce it to the point that a broken blade in the hand will not have visible grains to the naked eye.  How much finer beyond that is up for a lot of debate with a lot of variables.  

 

Normalization is generally the process of heating above critical (austenitization) and cooling in still air.  How high above you go depends on a lot of things, but generally there is no need to go more than 50C over.  Many people will also include a cycle a little below critical.  The best way to know if you are doing it right is to break a few blades.  Obviously, they don't need to be overly pretty, but general cross section and thermal history consistent with intended production process is important.  See what your grains look light by breaking the blade right after quenching.  

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Fyi, Rick Furrer made a couple of interesting vids n carburization or cementation of iron into steel.  Also the on line book called The cementation of iron and steel.. provided some interesting info.

Time and temp are key factors in depth of carbon the steel accepts.

Using a propane forge  at temps between 1850f and 2000 f have produced reasonable steels on 2-3 hours in both 1018 and wrought iron. Both had Rockwell  hardness of 55-60+ after normalizing, quench etc

Nice work 

,

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When it comes to sketching I prefer pencil.  I often start with really broad, fast lines.  Once a shape starts to appear I will take that and re-draw, sometimes several times until I get a fairly refined drawing.  Then I go in and work on the parts that don't flow. or I will make detail sketches of parts that I think will need more thought.  I have a couple of big pads that I use for full scale drawings, particularly for bigger stuff.  It's process for me, tiny variations in transitions make huge differences in the final product, and I can use them to keep me on track.  I often get lost forging and forget where I was headed.  That's not a bad thing, but sometimes I'm after a specific thing and I need help.

 

G

Edited by Geoff Keyes

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

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I haven't forged a lot of knives, but I have made some sword/knife blanks out of wood for casting. Usually I'll draw on the wood with pencil until I have a general shape I like, then cut it out and start carving. The nice thing about carving is you can adjust and modify the shape as you go. It's more work than just drawing, but then you have a 3 dimensional representation of what you're going for, and you can compare that to your work in progress. 

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