Recommendation? Bad Heat treat?

[K7JDD]

Hello all. New blade maker here. I have made about a dozen stock removal knives with 01 tool steel. I am getting better and really enjoy it. I am now starting to have a more critical eye on my technique. My concern is sharpness/edge retention. All my knives are heat treated in a DIY propane forge with Venturi burner and a thermocouple. I get the forge to 1450-1490 and put the blade in. Get it to the same color as inside of forge then quickly into a 140-150 degree can of veg oil. Quickly wipe and then into a 400 degree oven for two 1 hour tempers. This seems to work. I test them with those little hardness files and it usually indicates high 50’s for hardness.

Here is where it seems to go bad. I finish out the knife then sharpen. I have tried a few systems including the classics Lasky, a KO Work Sharp, BubbleJig and 1x30 belts and water stones. I can always get them fairly sharp but never as sharp as I think I should be able to. Sometimes I keep polishing the edge to a mirror and it gets razor sharp but not really. It seems to immediately loose its razor edge and I can run my finger over the sharp part. What am I doing wrong? Do you think it is in my heat treat? Sharpening technique? I can’t figure it out. I have searched around on the forum search tool and just get lost. Follow all kinds of tips and still same results.

 

[kuraki]

What kind of angle are you sharpening at? What does "razor sharp but not really" mean? If I understand correctly I think you are creating a very sharp wire edge which seems to be quite sharp, but then folding it over in use rather than removing it with a strop.

 

[HSC ///]

doesn't 01 require a soak time prior to quench?
how are you measuring sharpness? can you slice newspaper cleanly with no drag in a downward stroke, not across, but straight down, can you cut through manila rope clean? shave hair?

in terms of measuring the heat treat, can you chop thru a small nail? can you check your edge flex against brass rod or sharpie marker body

 

[joedhiggins]

Probably 2-3 factors.

The initial sharpness is not likely connected to your heat treat, though edge retention likely is. That procedure is significantly less than ideal for O-1, and with that setup, you would be far better off with a simple carbon steel like 1075/1080/1084. If your initial heat treatment was closer to ideal, your as temeperd hardness should be 61-62. That being said, While not ideal, it should still hold an edge through non abusive cutting tasks.

Initial sharpness is almost definately some combination of edge geometry and quality of your shaprening. I am assuming you cna get good results with the previously mentioned sharpening techniques on other blades. If so, we can guess it is probably a question of edge geometry. How thin are you grinding the edge prior to sharpening? Some ranges that seem to be generally acceptable are 5 thou thick for kitchen knives and 15-20 for harder use knives. I can say that generally 5 thou edges will cut even when their edge is quite dull. 20 thou edges generally don't.

There may be some aspects of your heat treat that affect initial sharpness (like carbide size), but unless your qualification for 'acceptably sharp' in a general use knife differs significantly from mine, I don't really think that this is the problem with initial sharpness. Either way however, get yourself some simple carbon steels and hold off on the O-1 until your heat treatment setup supports preheat and soak.

 

[joedhiggins]

Also, get the heat treat app for your phone. It is helpful.

 

[Ian Fifelski]

If you can, I would soak for a bit before quenching, maybe 10-15 mins. A 10xx steel would get much better results with a forge.

For sharpening, what grit are you using? If you want a wicked slicing edge, try a 220 grit belt and then straight to stropping on green chrome.
+1 on what J joedhiggins said about edge thickness prior to sharpening. Unless it is a chopper, .005 is an ideal edge thickness before sharpening. .010-.015 for a large bowie or chopper.

 

[Stacy E. Apelt - Bladesmith]

Whatever method you use to sharpen, it is necessary to strop te wire off the edge.A piece of 2" wide leather glued to a board and charged with green chrome polish will strop the wirre off and polish the edge to crazy sharp.

This is independent of how well hardened the blade is. You could sharpen a piece of unhardened steel just as sharp. It just wouldn't last more than a cut or two before it was dulled.

 

[K7JDD]

What kind of angle are you sharpening at? What does "razor sharp but not really" mean? If I understand correctly I think you are creating a very sharp wire edge which seems to be quite sharp, but then folding it over in use rather than removing it with a strop.

I had been doing free hand on the 1x30 at first. I think I got a couple off bad ones doing that. I then switched to the Work Sharp set at 22 degrees per side which seems to be a standard edge. I have had a lot of success with the Work Sharp before making my own knives. Now I have been having the best results on the 1x30 using the bubble jig. I usually set that at a 22degree or 17 degree. I also follow all techniques with some passes on green and red compound balsa strips and a few on plain leather.

doesn't 01 require a soak time prior to quench?
how are you measuring sharpness? can you slice newspaper cleanly with no drag in a downward stroke, not across, but straight down, can you cut through manila rope clean? shave hair?

in terms of measuring the heat treat, can you chop thru a small nail? can you check your edge flex against brass rod or sharpie marker body

I have always used the paper slice as my preferred sharpness test. I can usually get a good clean cut with a freshly stropped edge but it is almost as if the paper dulls the knife. It is the same with the shaving test. A couple good passes then dull. I have only tested the heat treat with hardness testing files. I also beat up some wood and do a little carving with some blades. No chips or breaks, just dulled edge.

Probably 2-3 factors.

The initial sharpness is not likely connected to your heat treat, though edge retention likely is. That procedure is significantly less than ideal for O-1, and with that setup, you would be far better off with a simple carbon steel like 1075/1080/1084. If your initial heat treatment was closer to ideal, your as temeperd hardness should be 61-62. That being said, While not ideal, it should still hold an edge through non abusive cutting tasks.

Initial sharpness is almost definately some combination of edge geometry and quality of your shaprening. I am assuming you cna get good results with the previously mentioned sharpening techniques on other blades. If so, we can guess it is probably a question of edge geometry. How thin are you grinding the edge prior to sharpening? Some ranges that seem to be generally acceptable are 5 thou thick for kitchen knives and 15-20 for harder use knives. I can say that generally 5 thou edges will cut even when their edge is quite dull. 20 thou edges generally don't.

There may be some aspects of your heat treat that affect initial sharpness (like carbide size), but unless your qualification for 'acceptably sharp' in a general use knife differs significantly from mine, I don't really think that this is the problem with initial sharpness. Either way however, get yourself some simple carbon steels and hold off on the O-1 until your heat treatment setup supports preheat and soak.

I hear so many different opinions about 01 for at home heat treat. Some say it’s super easy in a low tech setup and others say it is not good at all. I have tried soaking at the proper temps and it tends to scale a lot, which I know can damage the blade. I am able to fairly accurately control the forge temp using the thermocouple and air baffles. Could I try a preheat that way? I just recently had some success with a boric glass coating and running the forge rich. As far as grinds, my bevels have been less than precise. I have been using a crude jig and not measuring angles. I am going to start free hand grinding with the BubbleJig when I get my 2x72 up and running.

Thanks for all the info guys.

 

[K7JDD]

If you can, I would soak for a bit before quenching, maybe 10-15 mins. A 10xx steel would get much better results with a forge.

For sharpening, what grit are you using? If you want a wicked slicing edge, try a 220 grit belt and then straight to stropping on green chrome.
+1 on what J joedhiggins said about edge thickness prior to sharpening. Unless it is a chopper, .005 is an ideal edge thickness before sharpening. .010-.015 for a large bowie or chopper.

Maybe I am over sharpening? I run the blades all the way up to 1500 blue film belt on the 1x30, then strop. Am I trying to hard?

 

[Stacy E. Apelt - Bladesmith]

If your 1X30 is running as fast as the ones I have seen, you may have burned up the edge at those finer grits. The edge can get way over the temper point even if the edge doesn't turn blue. The rules for sharpening on a belt are wet, slow, and cool every pass or two. A hard flat backing is also important unless you are going for a convex edge.

 

[Drew Riley]

You might try sending a couple of blades for professional heat treat, then sharpen them as normal. This will rule out how much of your issues are affected (if any at all) by your home heat treat.

 

[Ian Fifelski]

Maybe I am over sharpening? I run the blades all the way up to 1500 blue film belt on the 1x30, then strop. Am I trying to hard?

For most blades, I do a 220 grit belt. This gives the edge microscopic 'teeth' that make it slice incredibly. You probably have guessed this but run the belt away from the blade, not towards it like you would for grinding.

 

[milkbaby]

I have always used the paper slice as my preferred sharpness test. I can usually get a good clean cut with a freshly stropped edge but it is almost as if the paper dulls the knife. It is the same with the shaving test. A couple good passes then dull. I have only tested the heat treat with hardness testing files. I also beat up some wood and do a little carving with some blades. No chips or breaks, just dulled edge.

It sounds like you have a wire edge. The wire is sharp enough to slice paper or shave but so weak and unstable that it turns over right away and you get that dull edge. See my drawing below:

A dull edge (drawing #1) is one that doesn't have both sides of the bevel meeting at a sharp and clean apex. Basically to sharpen you grind away metal from one side (or both by alternating back and forth) until it meets the other side at an apex, but unless you have microscopic vision, you don't know that's happened until you feel the burr which will be sticking out on the opposite side from where you were grinding (#2). Then you grind the other side to get the edge bevel you want (usually even for a symmetrical edge). But you can end up with a burr that is standing up, a.k.a. the wire edge (#3). It slices and shaves for one or two passes because it's so narrow, but then it collapses because it's weak (basically goes from #3 to #2 in the drawing).

You want a good clean apex like #4 in the drawing. There are a lot of different methods people use to remove the wire. A lot of people like stropping on leather or other material. Some people slice through a soft substrate like pine wood or a hard felt block. I use Japanese waterstones to sharpen and remove wire on the stone itself.

It's still possible that your heat treat is not good as a soft knife can still be sharpened to slice paper or shave. It just will roll over or deform a lot easier than a hardened knife. But make sure you're not leaving a wire edge first. Sometimes you can feel it or you can gently drag the edge bevel flat against toilet paper and it's possible that the wire will catch against it.

 

[joedhiggins]

I hear so many different opinions about 01 for at home heat treat. Some say it’s super easy in a low tech setup and others say it is not good at all. I have tried soaking at the proper temps and it tends to scale a lot, which I know can damage the blade. I am able to fairly accurately control the forge temp using the thermocouple and air baffles. Could I try a preheat that way? I just recently had some success with a boric glass coating and running the forge rich. As far as grinds, my bevels have been less than precise. I have been using a crude jig and not measuring angles. I am going to start free hand grinding with the BubbleJig when I get my 2x72 up and running.

Sure, you can try a preheat and soak using a forge and TC. I would recommend the addition of a muffle as well. The big problems with this setup are that you often have a temperature gradient from the burner aperture to the farther reaches of the forge can be significant. A piece of pipe or tube as muffle will help with this. Baffles will also help. nailing preheat temp should be less important than nailing the soak temp. I would generally say that O1 is sufficiently forgiving that some temp variance in the austenitizing soak is fine. I hesitate to give a number, but I would think that whatever the most stable you can get inside the muffle will be fine. It should definitely get you a lot closer to the ideal as quenched hardness.

I dont agree that O1 is a good basic steel for beginners. People likely recommend it because it will harden with a slower quenchant than the simple carbon steels. It also has a more complex heat treat requirement, I generally think that it is easier to spend the 20 bucks on a fast quench oil that will do 1070-1084 than to get all the stuff required to handle O1. I literally think it is just hardenability (and perhaps that is comes in every profile and thickness you could want) that pushes people to recommend O1 to beginners. Otherwise, it is pricey compared to the 10 series, can be harder to work with, and will definitely air harden, which can exacerbate certain mistakes.

Milkbaby's advice is good. If you don't have a leather strop, newsprint on top of a water stone works beautifully. A buffing wheel can also be used for a more aggressive stropping. This is dangerous, and I find that the results leave something to be desired on most edges, though you can get a blade to hair popping sharpness in about 30s between a belt grinder and a buffing wheel. I mostly use this on axes and hatchets, rather than knives, but YMMV. Also, if you do decide to use a wheel, watch a video or two, and stand on the side of the wheel opposite the direction it will throw the knife.

 

[K7JDD]

Wow...so much useful information! Thanks everyone. I am going to process all of this and try a few different things. I spent a little while last night trying to get a better edge on my latest knife and no luck. It almost ended up be a throwing knife. I think the two things I need to concentrate on are blade geometry and heat treat. Unfortunately I just got 6 feet of 01 in so I am stuck with that for the next few blades. I am having trouble finding 10xx steels for sale online. Do I need precision ground stuff? I have no surface grinder.

I also have intentions of building an electric heat treat oven. I have all the materials sourced and a solid game plan. I have been holding off because a local maker has told me electric ovens are horrible for 01 and I am better off with a rich burning forge. It’s a scale/decarb issue? What do you guys think? Should I build it now knowing I will move on to different metals in the future?

Again, thanks for all you responses to my questions. I really appreciate it.

 

[kuraki]

Wow...so much useful information! Thanks everyone. I am going to process all of this and try a few different things. I spent a little while last night trying to get a better edge on my latest knife and no luck. It almost ended up be a throwing knife. I think the two things I need to concentrate on are blade geometry and heat treat. Unfortunately I just got 6 feet of 01 in so I am stuck with that for the next few blades. I am having trouble finding 10xx steels for sale online. Do I need precision ground stuff? I have no surface grinder.

I also have intentions of building an electric heat treat oven. I have all the materials sourced and a solid game plan. I have been holding off because a local maker has told me electric ovens are horrible for 01 and I am better off with a rich burning forge. It’s a scale/decarb issue? What do you guys think? Should I build it now knowing I will move on to different metals in the future?

Again, thanks for all you responses to my questions. I really appreciate it.

That is nonsensical. It's like saying milling machines are horrible for drilling.

ETA: I imagine he says that because of the decarb and scale you end up with in an oven if you don't do anything to prevent it. I'll take a coating of anti scale and a proper soak at controlled temperature over running a forge rich and doing it by eye.

 

[K7JDD]

That is nonsensical. It's like saying milling machines are horrible for drilling.

ETA: I imagine he says that because of the decarb and scale you end up with in an oven if you don't do anything to prevent it. I'll take a coating of anti scale and a proper soak at controlled temperature over running a forge rich and doing it by eye.

Good to hear. I think that seals the deal. My next official project is to build the oven.

 

[JTknives]

I would take a heat treat oven even with out anti scale stuff over a forge any day for any steel. I’m sorry but a “master” saying that does not seam very smart. Maybe he still edge packs and heat treat ovens are not good for edge packed knives. Facepalm

 

[Grayzer86]

I would take a heat treat oven even with out anti scale stuff over a forge any day for any steel. I’m sorry but a “master” saying that does not seam very smart. Maybe he still edge packs and heat treat ovens are not good for edge packed knives. Facepalm

You may be a bit confused JT. Electric ovens are not good for edge packed blades, but you can overcome that issue by quenching with your blade pointing perfectly true north. This is all assuming you can’t find a prisoner to perform a stab quench. The stab quench makes a perfect blade regardless of temp control.

 

[Willie71]

One thing that gets overlooked is that there can be a few thousandths of an inch of decarb along the edge. A few passes on the grinder will take that off to good steel before you grind down to your final edge thickness. If you don’t clean this up, the edge will not hold beyond a few cuts.

Secondly, you didn’t mention geometry. What is the purpose of the knife, and who is going to use it? Most of my knives are under 0.010” at the edge before sharpening. I don’t do a lot of hard use blades, so slicing is what I prioritize. With simpler steels such as oil hardening tool steels and 10xx steels, 0.010” for general use is ok, and 0.005” for kitchen knives work well. With higher alloy steels such as z-wear, pd-1, cru-wear, 0.005” is the thickest I go. When I started making knives, 0.020” at the edge sharpened at 25dps was a common recommendation. That feels like a club to me know. My personal edc is 0.003” before sharpening at 10dps iirc. I’ve gone down to 5-6dps on a couple kitchen knives, and they cut!