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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #1  
Old 08-19-2016, 03:29 PM
dtec1 dtec1 is offline
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attempt at keeping a tang softer than the blade maybe a mistake?

hey guys so I got the HTin done on this batch so now for the fun part .... I did try something this time I don't usually do and I am wondering how it turned out....on 2 of the blades istead of dunking the whole knife in the oil right away I immediately put the blade and about the first inch of the tang in the oil waited a few seconds and then put the rest in I was trying not to harden the tangs as much as the blade thinking it might make it easier to drill... so anyway I ended up tempering all the blades at 375 I know that's low but I have been doing all of them low then use the first blade as a "test" and figure exactly where the temper should be on some of the others I have been doing this the last 2 batches cause i ended up having some too soft due to slight variations in the HT so i feel like i have more control this way usually the temper ends up about 425 for the blades quenched in oil (wich most are) and 400 for plate quenched blades.... any way i grinded one of the blades (that was still tempered at 375) put a edge on it and tested on a brass rod and it was much softer than i thought it would be just so happens that this is one of the blades that i tried to keep the tang softer so will dunking the blade and waiting a few seconds for the tang effect the HT overall? i was expecting the tang to be softer but the blade be just as hard as the other so i am trying to figure out if that could have been the problem or maybe i seriously overlooked something else
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  #2  
Old 08-19-2016, 03:44 PM
Doug Lester Doug Lester is offline
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Refresh us. Are you using a regulated high temperature oven or a gas forge to austenize the blades in? Also, what alloy are we dealing with here? How was the other blade that you held the tang out of the oil for a few seconds?

I see no reason that holding the tang out of the oil should effect the hardness of the rest of the blade. I've done it and I think that a lot of makers here have done it without negative effects. My first instinct is to say that you did something different in hardening that blade, other than holding the tang out of the quenchant, especially if the second blade hardened for you.

Doug


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Old 08-19-2016, 06:06 PM
dtec1 dtec1 is offline
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I didn't think it should effevt it either that's why I asked I am using a even heat oven the steel is 440c stainless. I haven't checked the other blade I just heat treated 12 blades starting on wendsday over night in LN then yesterday they all got tempered at 375 I ground one blade (wich was one of the 2 out of 12 that I tried keeping thetang soft I didn't want to do it on all of them since I haven't done it before) like I said I ground one today and expecting it to be much harder that wanted I tested it on a brass rod and it wasn't anywhere near as hard as I thought it would be for only tempering at 375 ( I temper them all at 375 to releave stress from hardening then I grind one and work my way up on the temper till its good and then that gives me a idea of where to re temper the rest at) I haven't ground any of the rest of them yet tomorrow I am going to grind the other one I attempted this on and one of the ones I didn't and see if there is a difference if ther is then I guess that is why if not then I will have to figure out what could have went wrong good news is I don't think Its bad enough to have to re do the whole process just temper lower than usual but I would like to know why if possible ya know
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Old 08-19-2016, 06:56 PM
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Ray Rogers Ray Rogers is offline
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I don't know why your blade is softer than expected but I do know that you can expect that the tang may not be as much softer as you hoped (assuming you get a successfully hardened blade eventually). The reason is that 440C is quite capable of hardening in still air, not quite as much as in oil but close, so that the tang seems likely to harden anyway ...


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Old 08-19-2016, 11:50 PM
Doug Lester Doug Lester is offline
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Ray answered the question about 440C, many would consider it an air quenching steel, especially in the thickness of a knife blade. I am also at a loss as to why the blade wouldn't harden in oil. Try testing the other blade and see how it came out. Also, is there a way that you can get the use of a Rockwell hardness tester?

Doug


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Old 08-20-2016, 12:04 AM
damon damon is offline
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why not drill your holes before HT?

that and invest in carbide bits.
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Old 08-20-2016, 10:52 AM
dtec1 dtec1 is offline
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very true about the steel hardening in air it seems some simple things have been flying over my head recently. don't get me wrong the blade isn't SOFT just softer than expexted for example last 2 times I did the 375 temper and work up when it was at 375 all sorts of chips and cucks came off when on the brass rod that did not happen this time I ALMOST didn't even do the brass rod test at 375 I was about to re temper at 400 since the last 2 times the steel was so hard ...glad I did. no hardness tester....sometimes I do drill the holes before hand but most of the time I use carbide but I figured maybe I could get those bits to last a lil longer if the tang was softer deffinitly just a experiment that is why I only quenched 2 blades like that
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Old 08-21-2016, 09:51 AM
dtec1 dtec1 is offline
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hey guys just thinking here...since I didn't really accomplish what I wanted with the soft tang. If I heated up the tang making sure to protect the blade half from getting hot either by having the blade half in a cup of cold water or I have a "cooling gel" that if I slather the blade in that it might help maybe even doing both. now as it was pointed out that 440c can harden in air but that was when it came out the oven at exactly 1875 deg.. if I heated the tang would it harden just the same or would it get softer due to the fact of heating the tang wont bring it to the exact 1875 quenching temp so would cooling in air still harden?? or maybe be soft??
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Old 08-21-2016, 01:31 PM
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Ray Rogers Ray Rogers is offline
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You can soften it with a torch but you'll want a LOT more than a cup of water. Put as much water around the blade as possible, expose only the part you want to soften ...


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Old 08-21-2016, 02:18 PM
dtec1 dtec1 is offline
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ok I may try this tomorrow on one just to see how it works I have this "staycool"gel I got from a welding supply a long time ago and it does work pretty good and its REAL thick so I may slather that all over everything but the tang and then sick that in water its thick enough that I think it will stay stuck to the blade even if its in water...maybe hang it from a bar over the top of a 5 gal bucket that would be enough water I think
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Old 08-21-2016, 03:17 PM
Doug Lester Doug Lester is offline
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Heating the tang with a torch will work as long as you don't go past the critical temperature which is going to be over 400? less than the 1875? you run your oven at. If you heat the tang enough that the steel goes through a phase change it will harden when it cools in the air.

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Old 08-21-2016, 03:30 PM
dtec1 dtec1 is offline
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ok I really don't have a way to measure the temp but I was planning on just heating until it just starts to glow (if even that much) then let it cool. seeing how you can ruin a temper and soften a blade just by letting it get to hot on a grinder I figured it wont take much heat to soften the tang....like I said I am only going to try it on one blade just to see how it goes I am really just trying to see if I can extend the life of the carbide bits I have for drilling. it would be awesome if I could soften the tang (without effecting the blade) enough that a regular bit would go through it but I would be happy if it softened enough that it wasn't so hard on the carbide and maybe get them to last a lil longer
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Old 08-21-2016, 05:20 PM
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Heating just until it glows is not a 'little bit', that's better than 1100 f....


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Old 08-22-2016, 07:19 AM
jimmontg jimmontg is offline
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Talking Save yourself trouble in the future Dtech.

Don't try to do a differential HT with an air quench stainless steel. As you are finding, it is more trouble than it is worth. Doesn't mean it can't be done, but just a lot of bother.

Easier to solder a plain piece of a 300 series stainless to the hidden tang, or if you have the means weld it on prior to HT. Welding high carbon steel is a little tricky, just remember to keep the parts about 400-500 degrees while welding and they won't crack and let them slow cool. 400 to 500 degrees should turn the metal blue btw. You can buy Tempil sticks as well for a specific range of temperatures.
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Old 08-22-2016, 09:40 AM
dtec1 dtec1 is offline
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ok Ray so am I right to assume your saying I don't need to get it anywhere near the glowing stage?

jim, I could weld it ( I am HORRIBLE with a stick welder my hands shake too much but I am pretty good with a MIG or even easier flux core) however these blades aree all full tang not hidden tang so I don't think ithat would fly....I can just keep doing what I am doing like I said I HTed 12 blades and only tried keeping the tang soft on 2 of them it was really just to see if it was a viable option to get the carbide bits to last longer. if it had worked out good then I would think about doing it to more of them on the next batch but it doesn't seem like that is going to happen. I think I will just start planning things out more SOMETIMES I will drill the hole before the HT but not very often I may start doing that more often...
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440c, bee, blade, blades, brass, cold, drill, edge, fixed blade, forge, grind, harden, heat, knife, make, makers, problem, quenched, rod, solder, stainless, steel, supply, tang, thickness


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