gearhartironwerks Posted October 13, 2012 Share Posted October 13, 2012 I'm not quite sure where this fits neatly into a catagory, but here it is: A friend and I just split the cost of a new Rockwell tester (Grizzly) to test our knives. I spent most of today getting the machine dialed in as per the Chinese instructions (some lost in translation), but nonetheless, everything seems to work as advertised with the rated coupons. What amazed me, in testing some of my existing blades, is that they tested a little lower than I had expected. For the carbon steel (5160-52100-1095) non pattern welded blades, the average was in the low-mid 50's on the C scale. I had expected higher for my chef knives. I have a controlled heat treat oven and have tried to adhere to suggested temps/quenching for supposed hardnesses from conventional wisdom. Wow...what a surprise reality is. I know there are a lot of variables to be dealt with and eliminated one-by-one, but this has made me a lot more aware that trying to 'eyeball' or use a magnet to judge the austentite temperature prior to quenching may not be the best way to go. I am thinking that for blades, a more scientific approach to testing a specific material, as well as more destructive testing is called for in my endeavour. My next project is a thermo coupled salt bath for heat treating prior to quenching. My hope is that it will help with heat accuracy, lack of scale/wharping, and eliminating some variables. XXXXX, this is a slippery slope! Feedback greatly appreciated. Thanks, John Quote Link to comment Share on other sites More sharing options...
Woody Posted October 13, 2012 Share Posted October 13, 2012 What temperature did you temper the blades at. All that may be necessary to get the desired hardness is temper at a lower temperature. Parhaps you should do a hardness test on a blade prior to tempering to see what your initial hardness is that will give you a baseline to start from. Quote Link to comment Share on other sites More sharing options...
ianinsa Posted October 13, 2012 Share Posted October 13, 2012 Hi John, Please send/post the add for your tester , I would love to get one, the thermocouple for my foge seems quite good for a cheap chinese job. i got it include when I bought a complete forge from China in 2006, and since then I have not been able to get them to send the thermo couples loose. Quote Link to comment Share on other sites More sharing options...
John McPherson Posted October 13, 2012 Share Posted October 13, 2012 Rockwell testing is pretty reliable on simple homogeneous steels in flat sections, not so good on odd shapes and tempered alloy steels. How do you know if you are testing the matrix, or the embedded carbide structures? They make sets of graduated files that give a better feel for abrasion resistance, which is what is more important in a knife. Field testing with feedback is a better way to improve your product, IMHO. Anyhow, it is just a number, don't get too hung up on it. Like MPG on cars, it is seldom the first factor most buyers look at. Price, Performance and Pretty are more important in the marketplace, not necessarily in that order for any set of buyers. Indeed, it is a slippery slope, but a fun ride overall. Quote Link to comment Share on other sites More sharing options...
basher Posted October 13, 2012 Share Posted October 13, 2012 Are you testing flat parallel section? I have found rockwell testers to be useless for testing blade profiles. I have to make flat sections to test under the hardness tester . blade profiles test low as the diamond deflects (slides a little) down the slope of the blade. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted October 13, 2012 Share Posted October 13, 2012 Have a blade tested by someone with a tester that has been calibrated. The China knock off may not be accurate. Still kicking myself for passing on a Rockwell tester I saw at an auction. They went for $130 each with all of the accessories. Quote Link to comment Share on other sites More sharing options...
gearhartironwerks Posted October 14, 2012 Author Share Posted October 14, 2012 Thanks for the responses. Woody: The heat treat: heat to 1500, soak 10 min, quench in atf at 125-150 deg, then temper 375 twice for an hour each. I've been using this pretty much for 5160, 52100, and 1095. Ian: thermocouple at Omega .com...about $50. for a K type. The Rockwell tester came from Grizzly.com. I split the cost with a friend. Basher: good point as I hadn't considered the angle of the grind affecting the diamond tip. I will now. Thank you. I can see that having the tester will require a fair amount of experimentation, and time. It's really pretty exciting and I'm looking forward to it. Dang, if I just didn't have to make a living... John Quote Link to comment Share on other sites More sharing options...
John McPherson Posted October 14, 2012 Share Posted October 14, 2012 Just include a small flat bar made from the same parent stock in each heat treat batch. It gives an accurate test piece to destroy, and saves your valuable blades from having indents from the tester that may act as stress risers. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted October 14, 2012 Share Posted October 14, 2012 Personally I think 10 minutes soak is to a long time for most blades... Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted October 14, 2012 Share Posted October 14, 2012 I have a reliable rockwell tester. I think for most folks they are not worth using, unless. You spend the time in your shop making a lot of blades and keeping accurate logs of wot steel you use, how you heat treat it and wot the testing results showed you. By that I mean you have to check test pieces for internal grain structure when hard.by breaking the test piece. You have to know wot grain structure need to look like. Then you need to temper test samples and see how they perform as blades. Wot tests and how you repeat them is up to you. ABS testing standards are a good start if you do not have your own ways. For me if you develop standards that work for you a Rockwell testor will allow you check in the future to see if wot you have develolped that work stays up to your standards. And that applies to each new batch of steel the you obtain. i tested the blades on two comercially made knives last year when a friend asked me to sharpen them. a file test seemd like they were really soft for blades. The h ardest of the two came out at 42 on RC scale. I suggested he break them both and toss the pieces. he has good knves now..so a tester can be nice to have. Quote Link to comment Share on other sites More sharing options...
gearhartironwerks Posted October 15, 2012 Author Share Posted October 15, 2012 Thanks Rich, I fully intend to do specific testing/destructive testing. I look at this as another means to an end so to speak. Without specific testing, one is really shooting in the dark, and 'eyeballing' the quench temperature is simply not good enough (to me) if one is selling knives. The parts for the salt bath are supposed to arrive tomorrow. I'm anxious to eliminate some variables... John Quote Link to comment Share on other sites More sharing options...
K. Bryan Morgan Posted October 15, 2012 Share Posted October 15, 2012 I plan on getting a set of hardness testing files. They are made in varying degrees of hardness. Once you find the file that skates across the metal your harder than the steel. I have a friend who uses them and I saw them tested against known hardness steels. They are accurate to within about 5 points of rockwell hardness. Which for me is plenty good. I saw a set for $85. Quote Link to comment Share on other sites More sharing options...
McClellan Made Blades Posted November 5, 2012 Share Posted November 5, 2012 John, I have a question/suggestion, I would strongly recommend getting some Commercial grade quench oil. With all you have spent on the tools you have, the quality steel you're using and you're still using ATF? I know a lot of people will say that it works just fine and many will have a great argument for using it, MY experience is all I can go by and the main thing I noticed in my blades when I changed from Canola oil, to Maxim Oil's DT-48 Quench Oil, it that my knives stayed sharper during my usual testing routine, actually, I tested them a bit harder after using the DT-48! Like someone else said, I would recheck your HTing times, to me soak times are determined by the blades size and thickness, I would say in general 10 minutes 'SHOULD' be long enough for most blades to get into solution, I say "should" because there's a reason metallurgy was once thought of as a "Black Art", there are so many factors as to the why's, the how's, and the, Oh CRAP'S! My only point is this, think about ALL, I mean everything you're putting in a single blade, why not have a quench oil MADE to do the job it is intended to do? I know there are guys out there that will jump up and down about this topic, and I am not posting to open that can of worms up. My experience has shown me that if I am going to buy all the best quality parts and pieces I can afford including the very best steel I can afford that will give me the performance I'm looking for, then why not give the steel the best possible chance to be ALL that it can be? I want to make this clear too, I am not a salesman, or have any ties to Maxim whatsoever, other than I was in on the bunch of guys from KnifeDogs forum that contacted Lee Neves at Maxim and discussed making this quench oil for us. If you don't know it yet, you will soon find out there are few quench oil makers that want to deal with knifemakers, much less talk to them on the phone about making it for us. He did step out on a limb and made up a lot of this oil for us. I don't know if he is their metallurgist or if he owns the place, I know that he also carries Parks quench oil, for those knife makers that want it. While he still makes the DT-48 for us as well, it is A LOT cheaper than the Parks, the last time I bought a 5 gallon bucket, shipped from Texas to Alabama was right at $100.00, that ain't a bad price at all. And I have quenched 1075, 1084 (mostly), 1095, and W2 in it, if you're wanting it faster, just heat up a chunk of steel when you're cooking your blade and put it in just before you put your blade in, that'll increase the viscosity of the oil and make it cool faster. Or if you're the more technical type you can heat your quench tank up to around 125 to 140, over 165 and you will not cool it fast enough, that's the break over number between cooling too fast and rendering your oil useless. Also, as some have already said, don't get too caught up in the numbers, your testing should tell you everything you need to know about your process. Also, keep in mind that getting your blade from the kiln to the oil as fast as possible is important as well, you want to do that in under or reasonably around a second or so, I have heard some makers say on certain steels, you have to get your blade from the HT'ing temp to a specific number(600 degrees) and (it was W2), in under a second, Lots to think about there, if I can be of any help I'll do my best to help in anny way I can. I don't like to discuss the type of topics that are left up to a lot of opinion, not that I won't give you mine, AND I will generally specify where my info comes from, if it is from my own experience I'll say that, if it is something I read somewhere, I'll say that, a lot of the time, I will say something that will sound like, I don't remember where I got this from,but I recall this ____. What I'm trying to say is if I know it, I'll share any and all of the info i have with anyone, I will never say that my way is the best way or the only way, I will say "what has worked for me is ______. I am by know means any kind of expert, I have been making knives only 4 years, so I still consider myself a Newby! But, at the same time I will share what info I do have and know. Hope this helps, Rex Quote Link to comment Share on other sites More sharing options...
gearhartironwerks Posted November 6, 2012 Author Share Posted November 6, 2012 Thanks, and an excelent response on the quenchent. I'm headed there one step at a time. My immediate focus is the business of making furniture, lighting, firesreens etc. Bladesmithing is still a fun and fascinating thing that happens mostly on Saturdays and at other times during the week that I can justify having fun without cutting into reality. I did sell 3 pattern welded chef knives this week and feel really good about that. They tested out at 58-60 hrc after tempering. I'll post pics asap. John Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted November 7, 2012 Share Posted November 7, 2012 I have exception to the part about "heating increases viscousity, and that equals a faster quench" I disagree. Normally colder is more viscious, and that slows down tioe quench speed. Heating an oil decreases viscosity, to increase cooling rates. Could you please explain ??? Quote Link to comment Share on other sites More sharing options...
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