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The Outpost This forum is dedicated to all who share a love for, and a desire to make good knives, and have fun doing it. We represent a diverse group of smiths and knifemakers who bring numerous methods to their craft. |
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#1
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How Thin?
With flat grinds, how thin are your blade edges before heat treat? After heat treat, how thin before convex sharpening grind?
Thanks. __________________ Mike Broach Knives made to be used. |
#2
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Mike I hope this question sparks alot of chat cuz I would like to know this stuff as well.
I have never flat ground a blade,,started off hollowgrinding and i feel like i skipped a step lol. Skip |
#3
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I havent a lot of experence
I guess it depends on a few things - hammer finish or sanded finish how good the blade was forge I think there are a lot of things that has to do with how thin Maybe I thinking worng? I really wasnt much help just stired the pot a little Ron |
#4
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I have been finishing mine completely before HT'ing. I don't like working tempered steel anymore then I have to. By using a very rich flame and a piece of insulwool over the tip the thin finished plunge/edge will get to CT real fast. All of my knives are edge quenched and since they are forged and I don't anneal afterwards, the spine is allready at air hardened temper. I only use 5160, 1080 and 1084 which generally don't need to be annealed in order to file or belt grind. You can still drill pin and thongs holes with good quality bits.
To check for CT I put the magnet into the forge so I do not have to bring the blade out thus exposing it to more O2. After HT'ing I soak it in 20% vinegar to get the oxidation off. Then I have very little sanding to do. This process works well for me but there are many other techniques. It's a matter of trying all of them and finding the right combo that works for you. Last edited by B.Finnigan; 11-05-2006 at 02:38 PM. |
#5
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Brent, with your edges completely finished, have you noticed any of the pulling apart in the time it takes to cool before tempering? I understand doing this with stainless steels, but you're one of the few I've heard of doing it with carbon steels because so many end up with cracked edges.
For what it's worth, I've always thought about 1/32 is where to take it before HT so that's what I try to do, I can make darn-fine letter openers and paperweights this way I'm pretty sure I got that number from someone off here, but I'm not positive. __________________ Cap Hayes See my knives @ knives.caphayes.com This quote pains me: -- "Strategically placed blood grooves control blood spray in covert deanimation activities." -- |
#6
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I know you blade smith guys have a lot to consider that stock-removal dosen't content with.
so i guess we need to ask Mike if he is forging or stock removal,, on a stock removal (hollow ground) blade I leave it .050 thick at the cutting edge then send it out for heat-treating that way if the blade is slightly bent when it comes back it can be ground straight. and I was told that any thinner and it will burn off. what say you??? |
#7
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Cooter, what kind of forge are you using? If it's gas then Brent's on the money with the rich flame. The old timers used to say, "Forge thick and grind thin a fine edge to win." I think they had problems with decarbing. I've also read a lot of older stuff that said knives didn't start performing well until they'd been sharpened a number of times. This got them past the decarbed steel. But of course there are ways to get around decarbing if you're careful. I think it also depends on the steel. I have problems with 5160 getting wavy on me if the edge is real thin. The simpler steels do better for me. I think you have to be really careful and aware of your temps. I'm pretty sure my biggest problem is getting the edge too hot, which makes it go wavy. I just did a 1080 blade that was taken to the finish edge. I heated it up real slow and when I saw the "shadow moving up the blade I quenched it. It got real hard and no warping. I was a happy boy.
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#8
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Skip, I'm a stock remover, but I've never really worked with stainless steels. That being said, I'll mention what I was told by Alan Folts. When he's using ATS-34 or S30V he takes his edges down almost to the point where they are ready to sharpen. That way when you get them out of HT just cleaning them up is basically enough to get the edge ready for sharpening. I never saw him measure one with calipers, but I would hazard to guess it's closer to .020 or .030
__________________ Cap Hayes See my knives @ knives.caphayes.com This quote pains me: -- "Strategically placed blood grooves control blood spray in covert deanimation activities." -- |
#9
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From what Im reading here the bigge is how thin depends on how good the control of the heat at HT . You know I think getting to hot at quench has caused some of my warping and cracking pulling the edge down.
Ron |
#10
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I wonder just how much over CT is safe?
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#11
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I use a propane forge and a 3" pipe with one end sealed when heat treating to reduce scale. I use a magnet to check temp. Until recently all my knives were stock removal. I am working on 4 small knives forged to general shape, then flat grind to final. I got my first distal taper forged today, almost no grinding required.
The routine now using 1095: forge to shape- refine with grinder to 240 finish- 3 heats to stress relieve- edge quench in 150 F canola oil. __________________ Mike Broach Knives made to be used. Last edited by nc_cooter; 11-05-2006 at 05:28 PM. |
#12
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Remember that the Curie Point (non-mag) is allready over the critical temp. So just hitting non-mag means you have allready shot past the steels CT.
Not over heating is very crucial. My forge is blown which allows a broader temp range and it is in the same lighting conditions so I can watch the color. When I say burning rich I mean alot of yellow flame on the outside of it. Pre-heating the forge is also crucial. I run it until the refractory is orange before I ever put the blade in. I do get a very small amount of edge burning but it is so small that just sharpening will remove it. By staying away from using 0-1,1095, 52100 etc. alot of problems are prevented. I always cringe when I read a post about a newbie starting out with 01 or 52100. They must figure that the veterans are using it so it must be great stuff. It is great stuff but it is also very unforgiving and tempermental to forge and HT at times. I have been forging for two years now and I still avoid the 1% and higher carbon steels. For the time being I will stick to the 1080's and 5160 steels until I refine the process. I really like not having to anneal after forging so I may never go to the higher carbon steals. Call me metalurgically spoiled. |
#13
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I usually take my forged blades to 1/16" before HT then go by feel....after you get ready to finish, feel the edge...moving your fingers from the spine to the edge, feel for your fingers to slide off the blade without a lot of drop-off....does that make sense? Then sharpen till you cut yourself....maybe thats just me good luck!!!
__________________ Remember... hit it while it's HOT!!! |
#14
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"Remember that the Curie Point (non-mag) is allready over the critical temp"
so watch for the shadows back down in the red color? I ve been heating to non mag + so Ive been way out of the ball park. That would explaine alot of my problems, decarb warps cracks just to much shock and stress. I have been leaveing about a nickel thickness to quench - then working to an edge.Thats a lot of meat when you work it down by hand. Ron |
#15
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The chart below shows that carbon steel goes from austenite to pearlite at 1333 deg but the Curie Point (non-mag) does not happen until 1414 deg. But without having a pyrometer imbedded inside the steel there is no way of thumbnail testing it until it hits non magnetic.
After learning this I take the edge down to final thickness and mag check the edge and not any higher up. As soon as the very edge goes non mag it is allready over heating. If I tested higher up then the edge will go even higher in temp. I know alot of people that edge quench but check for non mag somewhere higher up. With stock removal you have to heat the entire knife to CT whether you edge quench or not. So it would make sense to leave more beef on the edge to be sacrificial steel. Last edited by B.Finnigan; 11-06-2006 at 01:26 AM. |
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