Ground too thin pre heat-treat

[EGA]

Hi all. I'm new to knifemaking, and new to this forum.

I've only ever ground 4 blades before, and the first 3 were just a prep for the 4th - I'm working on a 7" santoku knife. 1/8" 1075/1080 from Admiral Steel. Here's the problem, I've ground the blade too thin pre heat treat. In the course of grinding in a distal taper, I have made the edge AND the spine at the tip as thin as 0.01". That's just the very tip, but the edge in about the front half of the knife is about 0.02".

I'm going to be heat treating this with very poor-man's tools - a very simple open forge made of a grill, charcoal, and a bellows made of a hairdryer with a metal pipe extension.

My understanding from reading here and watching youtube videos is that that edge is much too thin to go into heat treat and will warp. Is that the case? As I see it, I have two choices

1) Re-profile the shape. This isn't totally drastic actually, because I wouldn't really mind going as much as a half inch shorter.. Re-profile to the point of having ~0.03" on all edges.

2) Trying heat-treating as is.


Your thoughts?

With regard to warping, I wonder whether 2) would be worse than 1), in that, can I try heat-treating, and if there is too much edge warp, re-grind? Additionally, is it possible that the edge being so thin will prevent me from getting a good heat treat, either from it heating up too much or from not being able to quench fast enough as it will cool in the air very quickly.

 

[Stacy E. Apelt - Bladesmith]

That is a bit thin for a carbon steel. I would just dull the edge back a bit until it is around .020 to .030" thick at the edge.

When doing the HT, quench and count to 8, then pull out of the il, wipe off with an old towel, ansd straighten any mazor warp/twist with gloved hands. Immediately clamp between two flat plates of steel/aluminum that are 1/4" or thicker. Leave there for a few minutes, then temper the whole thing for two one hour tempers at 375-400F. Remove from the plates after the second temper is done and cooled.

Clean up blade and sharpen after the handle is attached.

 

[ten-six]

You can't put steel back on. Heat treat it and keep that knowledge. Deal with warping if/when it happens.

I did a kitchen knife in 1080 yesterday that was .020" at the edge and .003" at the tip and it came out fine. I heat treat with a 500K BTU blowtorch in one hand and the knife in vise grips in the other (i.e. no forge) and quench in 130 degree F canola followed by tempering in a $20 Walmart toaster oven. You don't need $10K in tools to do this but some things will be more difficult without them.

 

[JTknives]

I heat treat with a 500K BTU blowtorch in one hand and the knife in vise grips in the other (i.e. no forge) and quench in 130 degree F canola followed by tempering in a $20 Walmart toaster oven. You don't need $10K in tools to do this but some things will be more difficult without them.

Facepalm
Yes you can get away with hacked up BBQs and weed burners. But don’t expect much in the way of performance from that knife. Just because it gets hard does not mean it will hold an edge as good as the same knife hardened with the proper equipment and technique.

 

[EGA]

You can't put steel back on. Heat treat it and keep that knowledge. Deal with warping if/when it happens.

I did a kitchen knife in 1080 yesterday that was .020" at the edge and .003" at the tip and it came out fine. I heat treat with a 500K BTU blowtorch in one hand and the knife in vise grips in the other (i.e. no forge) and quench in 130 degree F canola followed by tempering in a $20 Walmart toaster oven. You don't need $10K in tools to do this but some things will be more difficult without them.

Thanks for the advice. Mine is even thinner than that, but i'm glad to know others are using a rough and tumble approach.

 

[EGA]

That is a bit thin for a carbon steel. I would just dull the edge back a bit until it is around .020 to .030" thick at the edge.

When doing the HT, quench and count to 8, then pull out of the il, wipe off with an old towel, ansd straighten any mazor warp/twist with gloved hands. Immediately clamp between two flat plates of steel/aluminum that are 1/4" or thicker. Leave there for a few minutes, then temper the whole thing for two one hour tempers at 375-400F. Remove from the plates after the second temper is done and cooled.

Clean up blade and sharpen after the handle is attached.

Thanks, I think I will grind back a bit, shouldn't hurt the shape much.
Thanks for the advice about straightening! I was wondering about exactly that.

When you say to quench for 8 seconds before pulling it out, I guess some of that 8 seconds will be the blade only, then I'll dip the handle in after a bit, correct? I understand I don't want to harden the handle as much

 

[Stacy E. Apelt - Bladesmith]

I agree with JT that many backyard HT methods seem to work, but there may be a lot of harness and good structure left out.

Remember that the standard "by eye" method of "heat to red and quench in some sort of oil" was used by smiths for a couple thousand years. It was the only way until the 1900's. Grandpa, great-grandpa, and great-great-grampa may have been the best smiths in town, but their hardest knives were around Rc 54, and the bulk were around Rc 48-52. That was considered more than hard enough at that time. Also remember that they used few, if any, powered tools to shape and grind the knife blade and sharpen it. One reason the big steel manufacturing regions were so revered is they had the most advanced technology at the time. A knife from there was likely to be superior to most others. This made manufacturers in Sheffield, and Solingen ( as well as other places) famous ... and wealthy. The name recognition and hype still exists for these places today - even though the quality difference does not exist anymore.

50 years ago, I considered a Rc 58 blade quite hard. Rc 55-57 was more than sufficient for 90% of knives. I'll bet my as-quenched was often Rc61.

25 years ago, it hadn't gone up much at all.

Today, we have better steel, better HT ability, better testing, metallurgy, powerful tools, and electricity to grind and sharpen the hardened knife. Most current makers consider Rc 57 a bit too soft.

 

[JTknives]

57rc is upper sword hardness lol. But yeah it’s funny to think about how things have changed. Even in the short-ish (25 years) time I have been involved. But yeah I remember 5160 and O1 being kinda the go to steel for a lot of us and we took them to around 58rc. Now it’s how hard can we go with out having a blade of glass with a handle. For example I’m doing a run of small neck knives and thy are 15n20 and hardened to 63rc. That straight up removes any hand work besides sanding from the process after heat treating.

 

[ten-six]

Facepalm
Yes you can get away with hacked up BBQs and weed burners. But don’t expect much in the way of performance from that knife. Just because it gets hard does not mean it will hold an edge as good as the same knife hardened with the proper equipment and technique.

Believe me, I know. It's the best I can do with what I have for the least amount of money which is key to me. I'm sure I could get better results with better equipment and have no doubt that farming the job out would yield results I may never attain. In fact, I actually have one of your forms filled out in my toolbox right now for just that reason. Considering that I have no disillusions about using my knives in a tactical situation and that they spend 99.8% of their time in my dresser drawer it works for me.

I was simply giving OP a different point of view. I've spent less than $200 on tools in the 15ish months I've been doing this. There's probably guys on here that spend more than that on consumables in a week. Speaking as someone that tries to do this as a hobby on the cheap I can attest it's very, very intimidating to be amongst the pros.

 

[milkbaby]

Facepalm
Yes you can get away with hacked up BBQs and weed burners. But don’t expect much in the way of performance from that knife. Just because it gets hard does not mean it will hold an edge as good as the same knife hardened with the proper equipment and technique.

Serious question, if his torch is hot enough to normalize and do descending thermal cycling to refine the grain, then why shouldn't he "expect much in the way of performance from that knife" made of 1080, especially a kitchen knife that's not a hard user knife? I would think the main issue is trying to avoid grain growth at the tip and edge from overheating, but he could do it at night or darkened workshop and watch for even heating and decalescence. And if his batch of 1080 is below the eutectoid, wouldn't grain growth be less of an issue?

 

[joedhiggins]

Serious question, if his torch is hot enough to normalize and do descending thermal cycling to refine the grain, then why shouldn't he "expect much in the way of performance from that knife" made of 1080, especially a kitchen knife that's not a hard user knife? I would think the main issue is trying to avoid grain growth at the tip and edge from overheating, but he could do it at night or darkened workshop and watch for even heating and decalescence. And if his batch of 1080 is below the eutectoid, wouldn't grain growth be less of an issue?

This seems about right, I haven't HTed a knife with a torch, suspect that decarb is a big problem, but if you can get around it, I would just be worried about overheating in austenitization if you tried for even a couple minute long soak. Also, maybe so guys have a perfect eye, but I have been smithing for several years, have a TC in my forge, and still can't say I am nailing a heat to within 25 degrees (at least not when I am not at or very near the decalescence point).

 

[JTknives]

Guessing temperature by eye is not very accurate at all. Even people experanced in the field are usually way off. The problem is your eyes adjust to light so what looks bright orange might look dark orange if you look at it for more then a few sec or if you been watching a forge or torch trying to get an even temp. It’s just the fact of life we can’t be nearly as close as an electronic devise. And when 10-20° variation makes a difference in the hardness out come it’s hard to look at torch or bbq with any seriousness.

Don’t get me wrong thoes things work but to expect to get good preformance from them is more a chance of luck then guessing the right color.

 

[JTknives]

Speaking of heat treating, I am closing off my heat treating service till after blade show west. I don’t have enough time as it is to do all the orders and knives for the show.