Didn't remove enough stock - what are my options?

S

SteveGallo

Joined
Apr 29, 2014
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So here's my situation...

making my first knife, all is well, 8.5" chef's knife out of 1084.

I know chef's knives have to be thin, but I was also very worried about warpage so I didn't take it down too far. I tried measuring with my bargain basement calipers but they're awful and I need to get new ones. Normalized at just past magnetic, quenched in canola, HT 3x1 hour cycles at 420 degrees in my oven.

I now find myself with an edge way too thick to sharpen (or maybe I'm just not good at it). I realize I probably should have removed more material before HT.

What are my options here? My files barely bite and I think it would take me forever and a day to significantly thin the blade. I've got a cheap 1x30 grinder and plenty of 60 grit belts for it, but I worry about ruining the hardness (i dip the blade in water after each pass with that though, takes forever). Could I re-anneal the blade, thin it, then re-HT it, or is that asking for problems?
 
Hand sanding with a hard backed sanding pad will remove hardened metal. Buy good paper, 3m or Rhynowet.
 
That is not a "mistake", it's just a change in design parameters. Sounds to me like you now have a medium-weight cleaver/heavy utility knife. I'd finish it up as such, and start over to make a matching much thinner chef's knife.

I'm not being a smart-alec... I wouldn't care to remove much stock from hardened steel with the tools you've got. It can certainly be done but you have to decide whether that much more labor is worthwhile to you. Personally, I'd put that time into making a whole new knife from scratch. :)
 
james terrio said:
That is not a "mistake", it's just a change in design parameters. Sounds to me like you now have a medium-weight cleaver/heavy utility knife. I'd finish it up as such, and start over to make a matching much thinner chef's knife.

I'm not being a smart-alec... I wouldn't care to remove much stock from hardened steel with the tools you've got. It can certainly be done but you have to decide whether that much more labor is worthwhile to you. Personally, I'd put that time into making a whole new knife from scratch. :)
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Always an option...I'll see how long it takes me to remove material when I get home and base it off that.

So to be clear, softening and re-heat treating isn't a good idea?
 
What's the thickness now? Or at least what are your crappy calipers telling you it is? Sand paper should make quick work of it in either case with course grit and a hard backing. How course you want to go depends on how much material you need to remove. Watch Nick Wheeler's video on hand sanding. Change angles and don't move to finer grits in your progression until all previous scratches are removed.

If you trust your skills and have a LOT of material to remove you can start with your belt grinder. Grind without gloves and dunk after each pass. Bare handed you'll feel the heat before you ruin your HT. Don't linger in one spot or press too hard at the tip.

Sure you can anneal, sand it down some more and re-HT, but you can't get as close to a final dimension on carbon steel as you can on a stainless so you would still have to hand sand eventually anyway. Depends on how much you really have to remove.
 
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It would REALLY help to give you a good answer if we knew how thick the spine is, how tall the blade is, what grind it has (probably full flat), and most important....how thick is the edge at the moment? If it's not outrageously thick.....take 60 or 80 grit quality wet/dry sandpaper, lay it down on a flat surface, and work the edge down. Or clamp the blade down and use a good sanding stick. With a bit of effort and time, you can take the edge down no problem at all. I know it seems like a LOT of work...but it goes faster than you think.
 
I'd update on the thickness but I'm at work...it definitely isn't OUTRAGEOUSLY thick - I pushed it through an onion with no problem, though it definitely was far from sharp. I'd guess the edge is around 0.5mm-1.0 mm, and the spine is probably ~1/16", definitely less than 1/8". I'll check again with calipers later and put pictures up, though the calipers suck and aren't reliable at all.

It's full flat grind, blade's 8.5" (shooting for 8.5" blade 5" handle). If sandpaper/my little 1x30 will do the job, then I'll give them a shot. What's the worst that could happen, right?
 
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The worse that can happen is the blade gets too hot on the grinder and ruins the temper. Keep a dunk bucket handy and use bare hands to hold the blade. (Ah I see Varga Knives said that already). Good luck with the knife!!! Would love to see pics if you get a chance!
 
No they will not. Let me clarify that statement. Will those files remove material, even at tempered martensite hardness? Yes they will. But you'll quickly trash those files. I understand the RC on those files is 70 for the Pferd and 72 for the Grobet. They will remove material...but I wouldn't even begin to use a file on tempered martensite. Especially nice files like those.
 
Since you said you hardened it yourself you could always anneal it, thin it down and reharden it. Thinning down hard steel is going to be a LOT of work if you're not OCD. For my chef knives I start with 1/8" or 3/32" and take the edge down to twenty thou or less before hardening. There is a little warpage at times you can fix during the tempers with clamps. You will be happier with less work to do after you harden the blade.
 
To soften it down can I just toss it back in my forge, heat it up to ~1500 and it'll be good to work?

I tried using 80 grit belts last night on my 1x30" and very little material was removed before killing the belts. I think softening it is my only choice, because I'm not happy with it as is.
 
You will need ceramic belts to cut the hardened steel. I was able to get them at home depot. You might want to try that before softening the steel. You can get good belts at supergrit too.
 
I'm of the opinion that you should start a new knife. You could chalk this one up to experience and use your current blade as a camp knife or something.
 
I would not use an 80 grit ceramic belt. I would use a blue zirconium 120 belt. They cut fast and cool. They also don't leave nearly as deep scratches as an 80 grit belt.
 
samuraistuart said:
No they will not. Let me clarify that statement. Will those files remove material, even at tempered martensite hardness? Yes they will. But you'll quickly trash those files. I understand the RC on those files is 70 for the Pferd and 72 for the Grobet. They will remove material...but I wouldn't even begin to use a file on tempered martensite. Especially nice files like those.
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I've always wondered about that.

Thanks for the advice!
 
SteveGallo said:
To soften it down can I just toss it back in my forge, heat it up to ~1500 and it'll be good to work?
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You don't need to go to 1500F. If you are using a forge, heat it to 1300F-1400F(red but still magnetic), 2-3 times. That will give it a sub-critical anneal(redneck spheroidize) without the risk of overheating and changing the grain size.
 
Yeah, what Rick said. I will occasionally re-harden a blade, it does not have to be a huge deal. Might be good to get some practice at it starting now. For sure you'll enjoy thinning it a whole lot more in an annealed state...
 
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