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Grind Hard
04-27-2012, 09:00 AM
Most of my pieces are in place now, I'm going to fire up the Turret and punch out some blanks, then grind them into knives.... then make handles.


My mentor told me what steel to buy, which I did. It's a carbon-steel, that's all I know.

Once I get the blank made I grind the edges to clean the punch-nibbles off then I "back" one side of the blank and pack them up to send to heat-treat.

I tell the heat-treat company what sort of steel I have and I tell them "knife heat treat please" and a week later the blanks come back to me.


The heat-treat is pure black-box. All I know is the blanks are quite soft and bendy when I send them, and when I come back they do NOT bend anymore, in fact if you try to bend them in a press-brake you will %*&*! up the tooling. :D (shuddup, gotta learn somehow. :D )

Anyway, any insight on what this "heat treating" process might be? I'm curious, maybe it's something I can duplicate on a small scale to do 2-5 blades at a time.

Euph0ny
04-27-2012, 09:23 AM
Heat-treating knife blades is not rocket science, though it demands a bit of attention to get the blade hard enough to take a good edge, while still maintaining enough toughness and resilience in the spine.

Here's a link to someone doing it in "primitive" fashion:

http://theguncounter.com/forum/viewtopic.php?f=36&t=18542

The magic about sending parts out for professional heat treatment is that it pretty much guarantees consistency from part to part and from batch to batch. If you only want to do a few for your own use, and don't mind ruining one from time to time (see link above), go ahead and try doing it yourself. If you search for "knife heat treatment" on the web, you'll find plenty of how-to information.

ETA: you should be able to pick up a copy of Wayne Goddard's book, the "$50 Knife Shop", for about US$12 new - it covers what you need to get started doing your own heat treatment.

Mcgyver
04-27-2012, 09:29 AM
Knife people have their own way about them, the following is in the context of general heat treating not knife stuff. Volumes have been written on heat treating, but i'll attempt to do it in a paragraph :)

inside the black box: certain steels, tool steels such as O1, have a enough carbon in them that when brought to the right temp, bright red, undergo a crystalline change that gets 'locked' in place if its quenched (rapidly cooled). The steel is then as hard as it can be. Often you let it down some or temper it by warming slightly - trading some hardness for toughness, i.e. make it less brittle.

lots more you can add, that's why there are volumes, but that's it in a nutshell

It is very easy to do; drill rod is usually O1 meaning it works best with an oil quench (different media = different rate of cooling). Make what you want, heat it up red hot (propane and IFB is my preference) and quench in a coffee can (not plastic!) of old oil. Voila, you have a hardened piece of steel. Temper, stone, grind as required. Some want to complicate it, I think a carryover from production where you need to be consitently within a hardness tolerance and reduce scrap, but in my experience you don't need much more than this to make all manner of tooling and cutters, its enough to get you started anyway.

Grind Hard
04-27-2012, 09:39 AM
That simple, eh? :)

What sort of oil? Can I use (say) old press-oil or motor oil drained from the car? I got both of those in abundance.

If so this is something I can experiment with over the weekend. :D This would be great for "experimental" knives, one-offs, and novelty/gift knives that I sometimes make.




I have a product, a specific knife for a specific application that I've made off and on over the years. Recently I was given the chance to buy some machinery, looks like I'll be able to bring this knife to a wider market, perhaps.

If that happens I forsee myself learning injection-molding as I can't make zillions of wooden handles. ;)

Anyway, it's a specific style of butchering knife for the poultry industry... I make a knife and a specialized scissor too, and I sell them to small chicken-processing companies... mainly regional mom-and-pops or local-butcher-shops.

THESE would continue to be professionally heat-treated, simply for liability issues. Blade fails in service I can blame Jerk-O Heat Treating Service. :P ;)

demerrill
04-27-2012, 09:52 AM
Not a bad place to start:
http://www.cashenblades.com/info.html

More detail:
http://www.google.com/#hl=en&sclient=psy-ab&q=kevin+cashen+steel+treat&oq=kevin+cashen+steel+treat&aq=f&aqi=q-w1&aql=&gs_nf=1&gs_l=hp.3..33i21.40277.43964.3.45807.6.6.0.0.0.0.6 8.333.6.6.0.TOZNWn8KGtU&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=256a287b594d26f7&biw=1227&bih=1052

David Merrill

Mcgyver
04-27-2012, 10:01 AM
what kind of oil?....the quench fluid determines the speed of the quench; there's o1 that uses oil, A1 uses air and W1 uses water. You can also use cold brine for an even faster quench.

Point being the difference between air and water and oil are what matter...not whether its 30 or 40 weight oil. I use whatever I've drained from a machine and it works, old motor oil will as well. While the engineer at a commercial facility probably can measure and influence the quench behavior by differing oils, not sure it makes any difference to what we're doing. There is also no law that you can't quench O1 in water but it's likely to crack; quenching W1 in oil will also work but it won't be as hard. We're pounding spikes with a 16oz hammer here, not putting Cartier's together :D

The only meaningful difference with proper quench oil I've heard is that it doesn't smoke as much. This would be nice if you doing it frequently as i does stink up the shop.

its use is a lot more than experimental knives etc, the most handy use imo is for making your own cutting tools. yeah I buy them where possible, but often you need specialty item, commercial is too expensive for a one time use or its just quicker. I've made taps (left hand, double start), d bits, milling cutters, hex and square broaches, gear cutters etc

but get some drill rod and have it. take pics and post them

lazlo
04-27-2012, 10:41 AM
Knife people have their own way about them, the following is in the context of general heat treating not knife stuff.

As a "Knife people", I should explain that in high-end knife making, more than any other craft, the quality of the heat treat makes the difference between a good and a great knife. There are generally three schools of thought in knifemaking:



The "heat it to non-magnetic and dunk it in some kind of oil" crew. These guys don't like the idea that metallurgy is a known science, and that you can look up the optimal heat treat recipe in an engineering book. For simple steels like 1084, W1/W2 and O1, this works fine. They use a variety of thin viscosity oils: canola, transmission fluid, ... You won't get complete martensite conversion, but it's good enough for most applications.


The "quench tank should be facing north, and done on a full moon" crew. These guys often have complex protocols involving multiple quenches, putting the blades in the freezer, etc.


The ASM Heat Treater's Guide crew. These guys have read, and understood, all the metallurgy books, follow careful, scientific protocols, test the blade after quench with a Rockwell hardness tester to check how much martensite conversion they got... These guys are often in the acknowledgments section of Dr. John Veerhooven (an emeritus metallurgist) books and scholarly articles: Howard Clark, Kevin Cashen (who David Merrill linked), Al Pendray...



As a rough generalization, most bladesmiths ("Hammer jocks") do their own heat treat. Most stock removal guys send their blades off for commercial heat treat to a place familiar with heat treating very thin cross sections at high hardness: Peter's Heat Treat, Paul Bos, etc. Peter's et al use salt pots, exotic vacuum furnaces with nitrogen quench, but they're firmly in the third camp, so if you're sending your blades off for heat treat, you're in the third category as well.

The datasheets from most tool steel vendors provide data showing the Charpy Toughness, hardness, retained austentite percentages for various austentizing temperatures, hold times, etc. Ideally, you want the crossover point between Charpy (edge) toughness and hardness -- for most common tool steels, that's at 59 - 61 Rockwell.

lazlo
04-27-2012, 10:56 AM
quenching W1 in oil will also work but it won't be as hard. We're pounding spikes with a 16oz hammer here, not putting Cartier's together :D

The only meaningful difference with proper quench oil I've heard is that it doesn't smoke as much.

Quench oils are rated according to speed. Like commercial hydraulic oils, commercial quench oils are a mineral oil base with "add packs" -- additives to modify viscosity, thermal properties, shelf life, ... The mostly commonly used quench oil in industry is Parks AAA, which is a medium speed (11 second) quench oil intended for medium speed tool steels like O1. Gunsmiths use Brownell's Tough Quench, which is relabeled Houghto-quench "G". Same stuff. Canola and mineral oil is pretty close to Parks AAA in speed.

W1/W2 are shallow hardening tool steels. They need to be quenched below the pearlite nose (800) under 4.5 seconds. I make a lot of blades in W2, and I use Parks 50, which is their high-speed quench oil. If you were to quench W1/W2 or high carbon steel in Parks AAA or canola, you'll get incomplete martensite conversion -- crappy heat treat, which is most visible in the form of lower hardness. But you can radically improve the quench speed of slower oils by preheating them: bladesmiths just heat a scrap bar and stick it in the quench oil. 120 - 150 is a good range if you want to speed the oil up.

Kevin Cashen's site has the transition diagrams for all the common tool steels on his web page, along with very straightforward cookbook recipes for heat treating them.

Tait
04-27-2012, 02:15 PM
GB,

Sending them out will make you the best knife right now. But, if you're anything like me, you'll want to do it yourself!

McGyver's comment that it's enough to get you started was true for me. I have quickly evolved in the direction of Lazlo's "3rd camp."

I started by heating O-1 to non-magnetic and quenching in oil. It's a lot of fun, but I ended up having to grind off some of the steel due to de-carburization (not sure of spelling).

Now I heat treat a stainless tool steel in a kiln with foil. [edit: the foil is to keep oxygen away from the super-hot steel. I also regularly test hardness of blades coming out of the kiln].

Fortunately, the journey has been a lot of fun.

dian
04-27-2012, 02:24 PM
"All I know is the blanks are quite soft and bendy when I send them, and when I come back they do NOT bend anymore,"

somehow i always wondered about that: soft steel is "bendy" and hardened steel is rigid. but we all know youngs modulus is the same for all steels in any state. so whats the storry?

also, i got some soft t-nuts recently. your supposed to heat them to 880c for 45 minutes before quenching. so apparently its not just "heat it read hot and quench". although iv done exactly that with drill rod many times succesfully.
but why would anybody make t-nuts from some crazy stell, where this doesnt work?

Grind Hard
04-27-2012, 02:24 PM
The ones I sell will be heat-treated.

However I want to play around with other knife designs, blank designs, and just noodle around with the process, that's why I'm keen on learning about the heat-treat.


At lunch I acquired two bottles of torch-gas, two metal buckets, some wire for hanging and a face-shield. Tonight when I get home I'm going to take a soft blank and have at it using some old transmission fluid. :)

I'll report back tomorrow either from my computer or my laptop at the hospital. :D

Jaakko Fagerlund
04-27-2012, 02:52 PM
also, i got some soft t-nuts recently. your supposed to heat them to 880c for 45 minutes before quenching. so apparently its not just "heat it read hot and quench". although iv done exactly that with drill rod many times succesfully.
If you just heat it up and don't hold the heat long enough, the crystalline change in structure of the steel is incomplete (austenite formation) and thus only the portion that had time (mainly the surface layer) to transform will harden properly.

The amount of holding at heat depends on the steel and its dimensions (rule of thumb is an hour per 25 mm thickness), so you need an oven for anything you want to heat treat "properly".

Mcgyver
04-27-2012, 04:20 PM
" i got some soft t-nuts recently.

Good god man, hopefully nothing to do with this thread! :eek:


http://bbs.homeshopmachinist.net/showthread.php?t=53988




















:D couldn't help meself

Grind Hard
04-27-2012, 04:33 PM
Good god man, hopefully nothing to do with this thread! :eek:


http://bbs.homeshopmachinist.net/showthread.php?t=53988

:D couldn't help meself


Aye lad, that'll harden your nuts right quick no doubt about it.












...what? :D

Tait
04-27-2012, 04:49 PM
The steel should go pretty much from the heat into the quench medium with minimal delay (for O-1, somethin like 6 seconds before you start losing some of the hardening potential).

When you quench, insert the steel more or less straight: an angle will cause torsion.

Also, submerging the steel will lessen the opportunity for the fluid to smoke and maybe catch fire.:eek:

You might want to decide whether you'd rather breathe ATF smoke or Canola smoke...

Grind Hard
04-27-2012, 04:51 PM
You might want to decide whether you'd rather breathe ATF smoke or Canola smoke...


This will be done outside. I am not experimenting with GLOWING HOT METAL and BUCKETS OF SMOKING FLUID in my workshop. :D

lazlo
04-27-2012, 06:03 PM
Good god man, hopefully nothing to do with this thread! :eek:

http://bbs.homeshopmachinist.net/showthread.php?t=53988

Yah, we don't want to hear about getting your nuts hard :)


Also, submerging the steel will lessen the opportunity for the fluid to smoke and maybe catch fire.:eek:
You might want to decide whether you'd rather breathe ATF smoke or Canola smoke...

You're supposed to minimize the amount of flashing (fire) to keep from charring the quenchant, but like Tait says, for something with a thin cross-section like a knife, you really want to stick it in straight, and you have to move it around to disturb the steam jacket, or the quench slows down a lot. The only way to do that is dunk it up and down, and each time you raise the blade up, it's gong to flash the quench oil. No way around it. If you stir a knife blade, it will often warp in the direction you're stirring.

No matter what you do, it's going to smoke. Canola actually smells nice -- like french fries. But I wouldn't use anything with weird additives in it, like ATF or motor oil, since you're going to be breathing it.

Canola oil is really cheap at Costco. You can also use mineral oil -- you can get gallon buckets of "vet grade" mineral oil at Tractor Supply Company. Real quench oil is somewhat hard to find -- Houghton doesn't want to sell it to individuals for legal reasons. I get my Parks 50 from a distributor in Fort Worth. You can also buy small quantities of quench oil from McMaster and Brownells.

customcutter
04-27-2012, 09:41 PM
If you are using a commercial heat treater, use someone who can do a cryogenic heat treating process. It only cost a little extra, and is well worth the money. It will add 1-2 points on the rockwell scale and the blade will hold it's edge at least twice as long. That was my experience with ATS-34. Also find out if you can get a discount on bulk quantities. I used to "team" up with a couple of knifemakers, and we would send in a minimum of 50 blades, there was a considerable discount.

Also, I didn't see it mentioned make sure you are grinding your blades before heat treat. I always rough ground (50 grit) my blades to +/- 1/16 on the cutting edge. That will save you a lot of grinding belts.:)

Customcutter (Ken)

Grind Hard
04-28-2012, 07:25 PM
Is there any merit to preheating the oil to say... 350 degrees F prior to quenching a blade?

See... I maybe able to acquire a deep-well fryer. If nothing else it will hold PLENTY of oil for quenching.

I can strip the heaters off and just use it as a tank if there is no merit.

On the other hand, I could drop a coil inside it and run cold water through it to bring the oil down to 50 degrees or so prior to quenching....


Ya know what... PFFFFFT on ya'll I'm gonna experiment. You there, Lazlo! Hold my beer. :cool:

lazlo
04-28-2012, 07:47 PM
Is there any merit to preheating the oil to say... 350 degrees F prior to quenching a blade?

See... I maybe able to acquire a deep-well fryer. If nothing else it will hold PLENTY of oil for quenching.

Dunno, but be careful -- flash point and even the slightest drop of water, sweat, beer...
My Parks quench oil instructions indicate the flash point is 285F.

The deep oil fryer is a tried and true method for heating up the quench oil though.

I'm building a salt pot for quenching, and even the low temperature molten salt makes me nervous as hell.

bob_s
04-28-2012, 09:26 PM
Is there any merit to preheating the oil to say... 350 degrees F prior to quenching a blade?



NO! Increasing the temperature of the quench medium will REDUCE the heat transfer rate, not what you want to do. You want to cool the material as quickly as possible.

Completely immerse the blade in the oil, and move it about. The increased convection will aid in heat transfer.

Grind Hard
04-28-2012, 10:25 PM
I of course would read the data on the oil, I just pulled 350 out of the air for an example.

I'll talk to the well-fryer person Monday. This model has a cover that closes as you lower the basket. With a bit of finangling I can "prob'ly" suspend the blades in the basket, and use the safety-feature. If I set this up inside the workshop, a kitchen-grade vent-hood will be installed over it.

The remaining question, what to do with the smoke/vapor. I'm in a residential neighborhood... I have an "understanding" about my business-hobby with the Local Enforcement... I don't want to be That Neighbor and antagonize everyone with noxious smokes.



Anway... I punched a dozen blanks today. Suspended them from wire and heated them one at a time with a propane torch until they were "red-ish." I then immediately dunked them first in some ATF. BLegh nasty smoke. Used motor oil did the same. Fryer oil... well that smelled better.

The results are... I need to work on my heating apparently. I'm thinking "more heat" for a longer period of time. While I manged to reduce the "bendy-ness" the edges were not quite right after grinding.

Out of twelve I got one good blade, that one I heated until it was "almost orange" and dunked it in the fryer oil.

Now this is going by my somewhat skewed color perception. I'll have to ask someone else to look over my shoulder while I am heating to get a second opinion on the color.

Grind Hard
04-28-2012, 10:26 PM
NO! Increasing the temperature of the quench medium will REDUCE the heat transfer rate, not what you want to do. You want to cool the material as quickly as possible.

Completely immerse the blade in the oil, and move it about. The increased convection will aid in heat transfer.


:eek:

:D

Ok thanks for that advice! Now, what about the other extreme? Chilling the oil?

Jaakko Fagerlund
04-29-2012, 03:24 AM
NO! Increasing the temperature of the quench medium will REDUCE the heat transfer rate, not what you want to do. You want to cool the material as quickly as possible.

Completely immerse the blade in the oil, and move it about. The increased convection will aid in heat transfer.
Just to point out, but some tool steels require heated bath, otherwise they develop cracks when quenching.

All the requirements for the heat treatment of some particular steel can be had from the steel manufacturer by asking or checking their website, the route I would suggest taking.

As for heating with a torch, you will easily get inconsistent results, loss of carbon on the surface, not stable temperature through the part and easily bend the part if one side heats up much quicker and the austenite formation will be insufficient if you don't soak the part at the required temperature for long enough.

Also, if you heat too much, the resulting crystalline structure will be coarse and that is not good in terms of polishing/sharpening/wear/crack resistance.

Tait
04-29-2012, 11:00 AM
NO! Increasing the temperature of the quench medium will REDUCE the heat transfer rate, not what you want to do. You want to cool the material as quickly as possible.

Grind Bastard, Bob's statement is probably correct for this particular steel and for this particular quench. It is probably important to realize there are steels that need to cool off more slowly (see Jaako's reply), and that some quench mediums are designed to be faster than others because different steels need to cool at different rates.

WAIT - did we ever figure out what kind of steel you think you have?

Also, as you move forward, you might consider making it out of stainless. I have a custom design, the use for which requires regular cleaning by soaking in bleach. A poultry knife probably needs to be similarly resistant to the cleaning process.

Tait
04-29-2012, 11:07 AM
Also, if you get a heat treating oven, most of the stainless steels are air quenched, or can be quenched by placing between plates of aluminum, which helps keep them straight.

My paring knives are made out of a martensitic stainless alloy and are 1/16" thick to start. Because they are so thin, I grind the bevels in after heat treatment.

What did you mean when you said the "edges weren't quite right"?

lazlo
04-29-2012, 11:10 AM
WAIT - did we ever figure out what kind of steel you think you have?

Agreed -- at this point, it would really help if you would find out what steel you're using.

Industry actually does use high-temperature quench oil (and salt) for marquenching. The issue is getting the steel from the austentizing temperature, when all the carbon (and other alloying elements) is in solution, to below the pearlite nose -- about 800F for carbon steels.

The thing is that heating the oil increases the speed by reducing the viscosity. Above a certain temperature, there's no gain -- as Bob points out, you're just adding to the heat load.

Tait
04-29-2012, 11:42 AM
The thing is that heating the oil increases the speed by reducing the viscosity. Above a certain temperature, there's no gain -- as Bob points out, you're just adding to the heat load.

At breakfast, I pulled out my copy of Tool Steel Simplified, my basic resource for non-stainless tool steel. The book is about selection of particular steels for tool making, and is not specific to knives.

If it's not beating a dead horse...

"The temperature of the oil is of importance. If the oil is either extremely cold or extremely hot, the quench will be slowed down, in the first case on account of higher viscosity, and in the second on account of the slower heat carrying ability. The best temperature range for efficient and uniform quenching is about 100 to 130F (38 to 54C)." p.223, 1978 edition.

[I haven't tried it myself to confirm - again, I've moved on to air quenching steels. But if it's in a book, it must be true. Just like stuff of the Internets.]

When you find out what kind of steel you have, I can find relevant snippets on that particular steel. For example, it says of oil hardening grades:

"In older type manually operated exothermic atmospheric furnaces, a defintely oxidizing atmosphere is required. Excess oxygen anywhere between 2 and 12% will do the job.
...
Oil hard may be hardened from temperatures between 1425F and 1525F. ...
Without preheating, place the tool right in the hot furnace and let it heat naturally until it uniformly matches the color of the thermocouple in the furnace. Soak an additional 5 minutes per inch of thickness, then quench in oil.
...
It is recommended that it be tempered between 375F (191C) and 400F (204C) to produce the highest hardness and satisfactory toughness."

I would add that 10-15 minutes seems to be the minimum for thin sections.

Anyway, I'm learning too and would glad to learn with you...

dian
04-29-2012, 02:59 PM
in conan, the barbarian they quenched the sword in snow. can anyone see a benefit in that?

Tait
04-29-2012, 04:36 PM
Throughout history, there have been all sorts of interesting quenching mechanisms.

From what I understand, certain steels benefit from a sub-zero treatment such as Dry Ice, and there is another benefit from a different mechanism to treatment with Liquid Nitrogen.

How cold was the snow in the Conan movies?

Edit: OK... 4 of the last 6 posts are from me. If that isn't threadjacking, I'm not sure what is. Somebody else's turn...

lazlo
04-29-2012, 07:02 PM
in conan, the barbarian they quenched the sword in snow. can anyone see a benefit in that?

It'll make you the governor of California some day.

Grind Hard
04-29-2012, 07:02 PM
I am not saying what sort of steel it is other than it's a tool-steel. This is competitive advantage, see. :)

I can tell you after checking with my mentor he's "always used very light oil or water with this steel, depends what is handy. Heavy oil should be avoided because of the smoke. Heat it until it's orange and hold it at orange for several moments before quenching. DO NOT let it drop into the red before quenching it. Go from ORANGE to BUCKET and keep it moving in the bucket."

lazlo
04-30-2012, 12:01 PM
I am not saying what sort of steel it is other than it's a tool-steel. This is competitive advantage, see. :)

Heat it until it's orange and hold it at orange for several moments before quenching.

The competitive advantage would be in advertising what tool steel you're using ;)

But your mentor is in the first bullet, above:

http://bbs.homeshopmachinist.net/showpost.php?p=765065&postcount=7

If you're using O-1, which you mostly likely are (the more high tech tools are air hardening), you'll get a lot more performance out of it by heating and soaking in a furnace at the proper austentizing temperature. Look up an O-1 datasheet or see Kevin Cashen's page (above).

Grind Hard
04-30-2012, 08:56 PM
Oh I tell customers its a propitiatory custom high-performance tool-steel. Well most of them anyway. I got one that I joke around with, told him it's medical-grade aerospace billet. :D

So. Furnace. Where do I get a SMALL one?

lazlo
04-30-2012, 09:16 PM
I got one that I joke around with, told him it's medical-grade aerospace billet. :D

:)


So. Furnace. Where do I get a SMALL one?

They're stupid-simple to make. Some K-23 firebricks, Kanthal wire (Ebay or a local HVAC shop):

http://www.freewebs.com/knifemaking/HT%20FURNACE.pdf

http://www.practicalmachinist.com/vb/general/heat-treat-oven-235129/#post1684306

https://groups.google.com/group/rec.crafts.metalworking/tree/browse_frm/thread/fb2633d6e326e2bc/f4520bffd3fff04b?rnum=1&_done=%2Fgroup%2Frec.crafts.metalworking%2Fbrowse_ frm%2Fthread%2Ffb2633d6e326e2bc%2Ff4520bffd3fff04b %3Ftvc%3D1%26#doc_f4520bffd3fff04b
https://groups.google.com/group/rec.crafts.metalworking/tree/browse_frm/thread/fb2633d6e326e2bc/f4520bffd3fff04b?rnum=1&_done=%2Fgroup%2Frec.crafts.metalworking%2Fbrowse_ frm%2Fthread%2Ffb2633d6e326e2bc%2Ff4520bffd3fff04b %3Ftvc%3D1%26#doc_502c311454a799ec

A pottery kiln works too, although you need to make sure it goes up to the austentizing temperature you need, especially if you're using something exotic.

Tait
04-30-2012, 10:17 PM
If you are buying new, Tim Zowada (http://www.tzknives.com/) is a great source.

If I wanted a new, small one, I would be very tempted to pick up an Artisan (http://www.evenheat-kiln.com/knifeovens/artisanseries/artisan688/)