Pro VS Amateur Heat treating?

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David LaFerney

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If two identical blades - say 1084 - are heat treated 2 different ways...

Blade A - Professionally heat treated to a near optimal hardness - say Rockwell 63 - by holding at the nearly ideal temp for nearly the ideal time and then quenched in the ideal quenchant.

Blade B - Heated to about the right temp and then quenched in salad oil to Rockwell 59.

Both blades are then tempered to RW 57 using the same number and times of tempering, but at different temps to reach the same hardness.

How would they differ?

I speculate that they would both take and hold an edge about the same but that blade A would be less likely to break. But I don't know that - which is why I am asking.

Thanks.
 
Rockwell is only part of the story. And I'm not even sure if it's the biggest part of the story (my opinion).
Proper or optimal heat treat brings about the most from the steel as far a grain refinement and structure is concerned. I've heat treated 1084 back yard style and with a controlled furnace. I can tell a difference on the stone and on the edge.
 
1084 is a poor example for this question, because it's just not very difficult to get it thoroughly hardened and tempered. Many people get excellent results HT-ing it with very basic equipment like a basic open forge and canola oil... and once the blade is finish-ground, I doubt I could tell the difference between a 1070/1080/1084 blade they HT'ed and one done by Peters HT.

A better example would be CPM-3V or high-alloy tool/"stainless" steels. They require higher temps, more time at those temps to get everything into solution, and they benefit from cryo treatment. Likewise, some of the more complex "carbon" steels like O1, 1095 and 52100 are a bit trickier than 1084 if you really want to get the most out of them.

As for the difference between sending it to a company like Peters, and doing it yourself with the proper pro-level equipment and techniques (as many makers do), the question is mainly one of cost vs. time. If one has a dozen or more blades to HT, there's no way a guy in his garage can do it for the same cost as Peter's... based on electricity, all the gear, LN, tool wrap, quenchants, Rockwell testing to double-check, etc. On the other hand, sending them out generally takes 3-4 weeks to get them back... so if that person wants to finish up a blade or two today, or only makes a couple blades a month, sending them out is not going to be cost-effective.
 
As James pointed out, your numbers and example aren't really good. I will give a better comparison:


HT of 1095 at home and professionally.

A) HT by Professional in a atmospherically controlled kiln. Cycling of the steel to refine grain followed by austenitization at 1475F and held for 10 minutes. Quenched in 80F Parks #50 and tempered twice at 425F.

B) Home HT in a 2BF or torch with heating to non-magnetic and a "little more", then immediately quenched in warm canola. Tempered twice in a toaster oven set at 350F.



In "A" the steel would be approx. Rc66 as quenched and Rc62 after the tempers. The structure would be hard martensite and fine grain. Edge would be strong and stable at proper angle. Finishing should be fairly straightforward, as decarb would be minimized. Surface should sand clean and even.

In "B" the steel would be somewhere between Rc 63 and Rc65 as quenched, and Rc 59-62 after temper. The structure would be a crap shoot of pearlite, martensite, and RA. Grain size would be unpredictable and vary. The edge would likely have varying hardness and places that would range from chipping to rolling. Edge life would likely be shorter than blade "A". Finishing would require sanding past the decarb and scale to get to the "good" steel. Blade finish could be plagued with lines and splotches.
 
The pro will always do a better job because they have the better equipment and experience. The results give you a known product/results. If you do it at home, you're just hoping and guessing.... unless you also have professional equipment.

Is it worth having the pro's do your knives? Absolutely. Not only do you get the confidence from knowing that the pro did the very best job possible with the alloy you gave them, but you can use their reputation as a selling point.
 
The reason that I asked the questions in the terms I did is because of this -

"The following tempering guidelines apply to 1084 that has been hardened to industrial standards. Knifemakers using other methods will have to adjust the resulting hardness numbers downward for the same temperatures..." Cashen Blades < The chart won't display right when I paste it, but you can follow the link.

Apparently "Knifemakers using other methods" In other words Me - will probably not achieve the high initial hardness (HRC 65 or so) that a pro shop can but could arrive at the same target hardness by tempering at a lower temp. I was just wondering if in this particular case it makes a difference in the finished blade. I realize that it does make a big difference in more complex steels and even in more finicky simple steels like 1095.

I was trying to figure out what would be the best tempering temp for my garage quenched 1084 and of course like everything else the answer is "it depends." Even though 1084 is considered to be easy to HT apparently there is still a difference in the initial as-quenched hardness that can be consistently achieved depending on the sophistication of the equipment - but final hardness COULD be the same if tempering was properly adjusted.

I found many example of "I temper X times at X temp and it works for me" all over the board from 350-450 degrees and 2 or 3 times. I just wonder how different those knives are from one another. For no particular reason I did 3 times at 400 degrees - because 400 seems to be about average, and if 2 times is good 3 times must be better. Right? Hopefully it's in the ballpark.

But really without the ability to measure hardness I don't know what the initial or final hardness is anyway so I can't possibly taylor the tempering to a specific result, because I won't know where I start or finish. For that matter I don't really know what rockwell hardness I would want if I could dial it in - 55? 58? 62? All I really know is that my finished knives take an edge and seem to cut alright and aren't damaged by normal use - and after some use they need touching up. Just like most decent knives. The reason I'm using 1084 is that apparently beginners can get pretty good results with it despite our state of ignorance. But how much better would they be with pro heat treating - even in 1084? How do you know if you are making a better knife or not? Or even just a "Good" knife?

Sorry this is so long.
 
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VaughnT said:
The pro will always do a better job because they have the better equipment and experience. The results give you a known product/results. If you do it at home, you're just hoping and guessing.... unless you also have professional equipment.

Is it worth having the pro's do your knives? Absolutely. Not only do you get the confidence from knowing that the pro did the very best job possible with the alloy you gave them, but you can use their reputation as a selling point.
Click to expand...

I am absolutely convinced that what you are saying is completely true - but at this point in my education I place a good bit of value in a shorter development cycle as I try and learn different things. When (if) I ever get some designs dialed in I will almost surely send them out in batches of a dozen or so - even if that only happens a couple of times a year.
 
To do a"pro" HT you have to know and follow the whole process, step by step . Final HRc ignores many things like original microstructure, TIME at temperatue for each step, and other details.
Learn some more about HT !!
 
The best way to get a good answer is to ask a good question:)

Tell us how you are doing the HT and tempering. So far all we know is it is on 1084.
 
I'm using a forge made out of a bucket and refractory with a 4 1/2" hole all the way through it and a 2" black iron muffler pipe in the middle of that - heat from a propane forge burner that I got from ebay. I heat until the tang is still magnetic and the blade is not then keep heating until the tang (noticeably a cooler color than the blade) is no longer magnetic - then quench in 3 gallons of used peanut oil. I'm saving for a bucket of parks 50. 3 - 1 hour tempering cycles at 400 F.

Maybe this is resulting in a decent knife (maybe not) - But what I'm asking is what would be the difference in the properties of one of these knives and an identical one that was expertly heat treated to the same final hardness. Little difference? Lots of difference?

I know that hardness is only one property, but it can be measured if you have the right tools, and apparently the same final hardness can be achieve at least 2 different ways - High initial hardness at quenching and then tempering at a relatively higher temp, or lower quenched hardness and tempering at a lower temp. So you end up with the same hardness, but how would the other properties differ in an "easy" steel such as 1084?
 
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In your HT description, the blade edge is almost surely overheated.....maybe by as much as 100 degrees. The tip may have been even more overheated. This isn't a fatal flaw in 1084, but will give a chippier edge compared to one done professionally.
 
My suggestion is to make a blade and test the heck out of it... chop, whittle, slice, dice, push it to the max, purposely abuse it... then break it in several places to examine the grain. This will let you know if you are overheating or otherwise harming the steel.
 
The first thing that caught my notice is that you have a solid refractory forge with a 4.5" chamber ( you didn't state chamber length). In this is a 2" pipe. That leaves very little space for the flame to swirl around, and it may make a very hot spot on the pipe. If a smaller pipe will fit the blade, that would help. Support the muffle with the least blockage of the ports possible, as blocking the exhaust gasses also creates hot spots.
A few photos of your forge front and back with the muffle in place would help us see any other issues. I don't recall any photos of it and/or any build questions, so I assume you just made it to your own designs. That may have been part of the problem. Tell us a bit more about the forge, mesurments, refractory type and method of build.


Make sure the forge is fully heat soaked before putting in the muffle or blade. Run on high for 10-15 minutes and then turn it down as low as it will run and still be stable. On a venturi burner, that will usually be well above HT temp.

Place muffle ( not muffler) in forge and allow to come up to heat - another 3-5 minutes. Personally, unless the forge has a hot spot, I don't use a muffle. I can see and watch the blade far better in the open forge. I wear Auralens AUR-99 glasses to protect my eyes when doing HT. Staring into a forge can damage your retinas.
Place blade in muffle and allow to start heating.

Move the blade in and out constantly, rotating it as well. A 16" pair of proper tongs would be a big help here over the pliers you are using.
Test the blade bevel near the edge for non-magnetic, not the tang. You test the blade by pulling it out of the muffle and touching it to a welding magnet stuck on the forge shell or on a nearby object. Immediately place the blade back in the forge after checking. Again pay the most attention to the edge area of the blade.......it is the blade edge you want to harden the best, right?
Watch the tip and edge for signs that they are getting hotter than the rest of the blade. Rotate and move in/out as needed to get an even color.

When The blade reaches non-magnetic ( hopefully over the entire blade surface), notice the color of red. Continue heating and moving the blade for a little while until it is just a shade lighter/brighter red than it is now. Pay especial attention to the edge color, as this is the steel you want to harden the best. At one shade brighter, the blade will be about 1475-1500F. Immediately pull the blade out and quench in a gallon or more of oil. Heat treatment by magnet and eye is best done with low light. I prefer to do it on a very cloudy day or at night. I love doing HT in the middle of big thunderstorms :)
 
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Stacy E. Apelt - Bladesmith said:
I will remind you that a week ago I advised you to slow down. You have been making knives a whole month, and you are worrying about things that don't matter yet and not learning the basics. It should take several weeks to make a good forge if done right. It should take a while to make a grinder. It should take a week or two to start and finish a knife project in the beginning. You are racing through all these in four weeks and wondering why things aren't working to their best. Slow down and take the time to read and learn.
Click to expand...

Actually I think you are confusing me with someone else. I finished my first "real" knife in February, and my second knife about 3-4 weeks ago. If I go much slower I'll be dead before I get one made for each of my Grand kids.

I'm sure you are correct in that I probably am overheating the edges the way I've been heat treating - I'll work on that. It's not what I was asking about in starting this thread, but still very helpful - so thanks.

Just in case anyone is interested the question was - What are the qualitative differences between a blade (of simple, easy steel) which gets (properly, but with basic equipment) heat treated in a backyard forge (not by me, more like by someone like you Stacy) and one done by a skilled technician using pro grade equipment in a pro heat treat shop - If both knives end up at about the same hardness? Assuming that the shop is able to reach a higher hardness at quench than can be achieved in a backyard forge.
 
If you take a 1084 knife, heat treat it in a "backyard forge", but done properly, that means the exterior lighting is low so you can see what's going on as far as phase changes, that the heat treater has the ability to cycle the blade in and out of the heat, as Stacy mentioned, in order to get a uniform heat across the entire blade, making sure that the edge and tip do NOT overheat, that diligence is taken to make sure that the steel is at the right temp (best way to do this is either with the magnet or by noticing the decalescense that takes place...the tang has nothing to do with it....we are concerned about the blade temp, and most important the edge/tip temp), that the heat treater can HOLD the entire blade at that particular heat for around 5 minutes (not super necessary with 1084 but it helps with the slight bit of extra carbon 1084 has in it), then I would not expect there to be ANY difference between that blade and one that was heat treated in a controlled oven. Not Rockwell hardness, not grain structure, no difference. If using canola oil or the like instead of fast oil like P50 to quench, then regardless if it was done in a forge or kiln, the canola may give a result a point lower than the fast oil. 130F canola is a fairly fast oil itself, but not quite as fast as commercial fast oils.
 
David,
My apologies. I get a lot of email and PM inquiries and one was very similar to your thread. I was confusing his request of that morning with your question. I edited the post to remove the reference. Sorry.

Stuart is correct in that done to the best procedures in a back yard setup vs a professional setup, a "properly" HTed 1084 blade will be the same in either situation. Tempered martensite should be (mostly) the entire structure and edge stability should be excellent.
As soon as the steel type changes, the whole thing changes, and the professional HTer will produce a blade with better martensite structure and lower RA.
 
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samuraistuart said:
If you take a 1084 knife, heat treat it in a "backyard forge", but done properly...then I would not expect there to be ANY difference between that blade and one that was heat treated in a controlled oven.
Click to expand...

Thanks - I'm a little bit surprised at the answer, but that's what I was after. I guess it just goes to show that it's more about the skills of the craftsman (and choice of materials) than the gadgets they use. That shouldn't be a surprise.

Stacy E. Apelt - Bladesmith said:
My apologies. I get a lot of email and PM inquiries and one was very similar to your thread.
Click to expand...

No problem at all - You've been nothing but helpful.
 
"......it's more about the skills of the craftsman (and choice of materials) than the gadgets they use. That shouldn't be a surprise....."


That is the absolute truth in most crafts.

A skilled sculptor can carve a statue with a rusty pocket knife....an amateur can't do it with every tool in the shop.

I often caution new makers from buying all sorts of high end equipment when they don't know how to make a knife yet. All that is needed to make a good knife is a file, some sandpaper, and lots of time and effort. Once you can make a good knife with those, you can then refine those skills with better equipment.
 
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