1084 edge rolling but no chipping.

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moraldilemma666

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Mar 15, 2013
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Hi everyone just sharpened the first of three fixed blades im working on and decided to test the edge. got shaving sharp with normal effort felt like fairly hard steel. knife was quenched in pre heated canola oil and tempered twice for two hours at 400-420 degrees (sorry toaster oven wouldnt hold 425 i was aiming for) temp verified with thermometer. had maybee 1/16 " of steel before ht and then ground with norton blaze 120 grit till almost had an edge and finished with stones by hand. ( 30 degree inclusive scandi grind) now like i said it cut very well and still does. shaved hair after medium stone no problem. cuts wood shavings easily and well. the only problem i had was when trying to chop with reasonable force( not a full on swing just a little swing from say 6-8 inches away. going into the end of a block of pressure treated lumber. so just like battoning with the grain and had the edge roll what i would call relatively significantly on about 1/4 inch of edge roll was easily straightened with a steel and knife still cuts well with no chipping. is this normal? or did I do something wrong along the way. I was carefull not to overheat the steel during grinding post ht but is it possible that as the edge got very thin it heated too much? any suggestions or input would be greatly appreciated.

Thanks all.
 
also will be testing the other two blades asap. just havnt had time to grind them out yet and wanted to get some opinions here beforehand. ht was done in succession for all three with a propane forge. maybee I heated the oil too much and this one was last? dunno had about a gallon of oil heated with a slab of mild steel all knives are 1.5" wide 8" long and .140" thick
 
Anyone? Is this just normal at a steep grind angle for 1084? was aiming for rc 58-59 steel felt very hard with a file.
 
I would guess that the edge may have gotten hot once it was very thin. It can be tough to tell since it's so thin that it head very fast, but also cools very fast. I had a knife in 1084 that I was testing act this way. It got scary sharp, but had issues with edge rolling. I sacrificed it to the vice and strong arm, and it snapped off without taking a set, other than the 1/8 inch at the edge. I tracked the problem down to too low of a temper, (based on the way it snapped) and overheating the edge when finishing.
 
Should not roll over. Do you have a way to tell temp in the forge? Chipping means it is too hard, rolling means it is too soft. Somehow you must have overheated it after HT.
 
I have a 1084 blade (1/8" thick) I tempered 3x @ 400 and the edge rolls a bit. I have another (1/4" thick) that I tempered 3x @350. It cuts like a champ.
 
Thanks for the input. Sharpened another one even more carefully last night and its not as bad but still rolls too easily. Will be re ht the last of the three before grinding and temper at a lower temp. These two are meant as Xmas presents for family who barely use knives so doubt they will mind them being a little soft. And I'm almost out of time. Would seem to me that after being extremely carefull not to overheat the second one while grinding that my problem must be in ht or tempering. No temp controll on the forge. Though did have a magnet and table salt... Being as table salt melts right around quench temp for 1084 the shade of the steel also seemed good held till just after shadow was dissipated along the blade. So red orange USB color. Sorry for longwinded but typin on iPod touch ...
 
May not of got hard enough in the first place. I do a lot of scandi grinds and I used to work with 1084 and that never really happened with that temper. Maybe try and blunt the edge down a bit and put a little bit better than a micro bevel and see how that goes. Might just be to thin of a edge. What color was the blade when you got it out of the quench ? Lots of decarb or was it a smooth silvery gray ?
 
When you say held till just after the shadow dissipated, what do you mean by that. Sorry I could be missing something simple but I wanna make sure I understand what your doing here.

When I use my toaster oven for tempering (only thing I have right now) I have the tray wrapped in about 4 layers of tin foil. I have another layer of tinfoil that I place on top of the blades when I put them in there. The rack is raised above the element to the highest spot and I usually try to preheat it before I temper the blades. When the ovens cycle the elements just go to full bore till the temp is reached then they shut off. This can cause temp spikes which the tinfoil helps to midigate.

Another thing I only use the bake setting. On mine that only uses the bottom elements so I make sure the heat is hitting the bottom of the tinfoil first.
 
Marko3- After quench I did not have any decarb at all really just a dark grey uniform color over the steel. I do believe the toaster oven to be most of the problem as I did two 2 hour cycles set at 425 and registered only 390-410 on the thermometer at front of oven( Ill test it in the middle next week) I will try a different sharpening angle if the one I re ht comes out bad as well.

quint- I had a uniform color throughout the blade of a bright red orange and the " shadow" that runs throught the steel had all but completely dissipated I believed that this meant the carbon was completely in solution or had completed the transformation into austenite. please correct me if I am wrong. I had already passed non magnetic and would say that the steel went approximately two shades brighter/ lighter

Edit: Thanks to all of you for your time and help so close to the holidays.
 
You can use a baking dish of sand to help level out the temperature swings and protect the edge from radiative heating. Heat the sand to temperature then bury the blade in it for the temper.
 
Update on my blade tempered @ 400˚. Sharpened it a couple of times and the edge stopped rolling. Now it cuts like a champ.
 
My first guess based on the problem going away with a few sharpenings is that you had decarb still, although dry abrading will ruin the first few microns of steel before the rest of the blade even gets warm to the touch because of how slowly steel conducts heat

-Page
 
I think I'd rather temper by color with a torch than trust a toaster oven thermometer.
Even in my regular oven I also give the blades a loose wrap with foil to keep them from getting a hot spot.

Mark Aspery says one of his secrets for proper tempering is to only do it on thursdays and to always stand facing east.
Someone invariably challenges him, and he explains, "My wife goes and plays bridge on thursdays, and if I face east I'll see her if she comes home early and she won't get annoyed that I'm using her oven for tempering tools."
 
I temper in the kitchen oven. I put a cookie sheet on the bottom rack to block infrared and convection, I put a fixture that elevates the knife an inch above the cookie sheet on that, and a cookie sheet on the top rack. I have a small pile of pizza stones on the bottom of the oven over the spot directly heated by the burner to add thermal mass and block infrared, and I preheat the oven for a half hour with all of this in place before the blades go in. Toaster ovens are horrible for tempering, almost as bad as torches. I put the blades in clean so no oil burns off in the oven, the only issue my wife has is that every time she thinks I am baking bread (she loves my bread and pastry baking, as well as my homemade lasagne) it turns out I am baking blades so she ends up dissappointed

-Page
 
That's funny Page. :)

My last blade I did in the big oven. I don't trust the little one. I can see the elements cycle on and off, regardless of setting. Maybe with some crazy insulated thermocouple pid set up, but at some point it just becomes a couple of donor elements and a knob.

I like the suggestions for insulating in the big oven though. I just threw the blade on a cookie sheet, but better, more even heat wouldn't break my heart. I have some double wall (air gap) insulating cookie sheets that I'll try next time, but even as is, it seemed to do a good job.

Now to figure out how to even the temp in the forge. Very thin/pointy tips are worrying me.
 
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