Newbie trying my hand at two O1 knives

MDelConte

MDelConte

Joined
Feb 8, 2019
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New to the craft and doing some research for my first set of knives. Two matching O1 knives for my brother and I. I’ve also made a couple O1 mortise chisels that I tried heat treating in a two burner Devil forge before trying my hand at heat treating the knives. I got them to non magnetic and then a shade or two hotter and let them soak for 10 minutes while trying not to overheat them. I then quenched in vegetable oil. I have some canola coming and am thinking about just spending the money on some of the parks AAA... after quench I tested the hardness with a set of hardness testing files and they were around 45-50 Rc. Not what I was hoping for. I tested before tempering but in my understanding, tempering drops the hardness some while toughening the steel. The harder files would bite. I read something about decarb and that it might just be the surface that is still soft and that I need to grind down to get to the harder metal. I haven’t don’t that yet as I want to keep the dimensions of my mortise chisel and wouldn’t want to grind off much from the knives either. I see so much information on these forums but sometimes it’s contradictory or seems that way to me while I’m still learning. Planning on saving up for an evenheat oven so I can properly heat treat my blades and chisels in the future (planning on making many more) but for now all I have to work with now is a gas forge. I have also read some people saying to use a steel pipe capped at one end with a bit of charcoal to consume the oxygen in the pipe so I can keep a more even temperature. Thanks for any input/help!
 
O1 is easy to harden but trickier to get the best out of it.you have enough tools to get a good blade or chisel
Have you enough oil to really dunk the blade and agitate it?
I'd try file away any decarb like you said and test again and if your still doubtful just re heat treat it again
 
Those numbers indicate you are not down to HARD steel that is the soft decarb layer you are testing. Grind or sand down in an area away from the edge and test Clean steel. You should always plan to leave enough material to do final clean up after heat treating because you will always have Decarb with simple steels like O1. Even with a commercial heat treat furnace there will be Decarb.

Welcome to the Forum....
 
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You always make the blade/chisel/tool larger than the finished product so you can grind/sand away the decarb and leave a proper finish. About 5% is normal, depending on the metal type, how you will shape and finish it, and how the HT will be done.

Your HT sounds a bit iffy. I suspect they were far hotter than you thought they were. O-1 will harden like you did it, but will be much better done with controlled heating in a HT oven.

I suspect that there is a good layer of decarb to remove on your chisels. Don't worry about it on the shank, just grind the cutting tip back a tad. I would take it to your normal chisel sharpening jig/fixture/machine and shape the edge as normal. Test it with some cuts on wood.

Hardness files are better than nothing … but not much better.
 
A pipe muffle with a K-type thermocouple probe, sealed on both ends with soft firebrick plugs (coated with satanite, probe stuck through proximal plug), and something inside the muffle to consume the oxygen, will work wonders for holding a steady temperature and preventing decarb. I insulated my pipe muffle 270 degrees with insulwool coated with satanite to keep the temperature even better controlled. Blade/chisel sits on a piece of soft firebrick inside the pipe muffle. You control the temperature by fiddling with the gas flow while watching the thermocouple reading. You can do a reasonably accurate heat treat this way with minimal decarb.

In terms of your mortise chisel, it's still going to be a mortise chisel, just the next size down. You'll have to grind down the tip and all 4 sides to get to hardened steel. The procedure would be: grind, test, grid, test until you get to hard steel.

BTW, when I was starting out, I made some O1 dovetail chisels with my pipe muffle that turned out great with minimal decarb.

Mike
 
Thanks everyone for your input! I would be surprised if I didn’t get the chisel too hot. What would that do during heat treat? Does it lead to grain growth? Also I am positive I didn’t have enough quench oil. I probably had around 20 oz... I know it wasn’t enough. Until I can get something like parks or another designated quench oil, I plan on getting a 5 gallon bucket and putting around 3 gallons of canola oil in it. I’m hoping that is a sufficient amount of quench oil. Out of curiosity, what happens when you quench with an insufficient amount of oil? Guessing the oil gets too hot and doesn’t cool the blade fast enough to harden. How thick can I expect the decarb layer to be? Are we talking a couple thousandths? When you guys grind after heat treat, are you just grinding the main bevel or are you sanding/removing material from the entire blade except for the tang? If there’s a “soft” decarb later on the sides of the blade that isn’t removed, wouldn’t it scratch easier with use?

Is it necessary to soak O1? Is that a step to get finer grain size? This was a piece of precision ground stock, not forged. That being said, I read in another post that normalization cycles aren’t needed for a blade that’s not forged. But do normalization cycles refine the grain size? If so, could I normalize a couple times, then get to temp, hold for 30 seconds or so since the chisels are thicker than a blade, then quench? Should I be tempering as soon as the blade or chisel is back to room temp? Was planning on doing two 1 hour cycles at 400F.

Also, do any of you know where I could send the knives for HT for a reasonable price? I’ll have a good amount of time in them when they’re ready for HT and would rather get the most from the steel than have an ok blade.

I really appreciate you all taking the time to read and respond. I know I’m all over the place. I just have so many questions and want to better understand the knife making process.
 
MBB, trying to better understand the pipe muffle. What kind of pipe are we talking about? Do you cut a piece off a muffler or is this a purchased piece? Guessing the firebrick can be pressed into the end and twisted to cut into it or at least mark it, then satanite to seal. Do you do that every time you use it? Won’t the satanite crumble when you take out a plug? Also, not sure what the proximal plug is. Could you clarify? Is it just whichever firebrick plug is in closer proximity to the blade? I’m guessing the thermocouple wire is high temp but seems like it should be kept from a direct flame. Would you keep that end of the pipe at the open end of the forge? As far as insulating it goes, I think I get that. Pipe wrapped with insulwool, then coated with satanite to rigidize.
 
Since you are not Forging there is no need to Normalize/Refine Grain Structure...Yes Overheating will increase Grain Size. STEEL BUCKET for Oil you don't want a plastic melted oil fire! The Objective of the Quench is to bring down the Austinizing Temp of the blade as Quickly as possible that is the reason for different quench oils and quench oil speed for commercial grade quench oils. Canola is quick enough for slow through hardening steels like O1 when the oil is heated to 110-140F (Tip:you can heat a piece of scrap steel and use it to heat the quench oil).

Here is a Link to a Forum member who offers Heat Treating Services
https://www.jarodtodd.com/
 
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Busto said:
Since you are not Forging there is no need to Normalize/Refine Grain Structure...Yes Overheating will increase Grain Size. STEEL BUCKET for Oil you don't want a plastic melted oil fire! The Objective of the Quench is to bring down the Austinizing Temp of the blade as Quickly as possible that is the reason for different quench oils and quench oil speed for commercial grade quench oils. Canola is quick enough for slow through hardening steels like O1 when the oil is heated to 110-140F (Tip:you can heat a piece of scrap steel and use it to heat the quench oil).
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Thanks Busto. I will definitely use a steel bucket! Don’t want to burn down my house!!! I used a scrap piece to heat the oil last time and just got a long thermometer to clip on the bucket when I get it. From what I remember reading, the soak is to dissolve the carbides or free up the carbon and get it into the crystalline matrix. Something like that I think. Not a metallurgist but I’m sure you guessed that! Would I get a decent hardened blade if I got it to temp and held for about 30 seconds and quenched?
 
Busto said:
Since you are not Forging there is no need to Normalize/Refine Grain Structure...Yes Overheating will increase Grain Size. STEEL BUCKET for Oil you don't want a plastic melted oil fire! The Objective of the Quench is to bring down the Austinizing Temp of the blade as Quickly as possible that is the reason for different quench oils and quench oil speed for commercial grade quench oils. Canola is quick enough for slow through hardening steels like O1 when the oil is heated to 110-140F (Tip:you can heat a piece of scrap steel and use it to heat the quench oil).
Click to expand...
Thanks Busto. I will definitely use a steel bucket! Don’t want to burn down my house!!! I used a scrap piece to heat the oil last time and just got a long thermometer to clip on the bucket when I get it. From what I remember reading, the soak is to dissolve the carbides or free up the carbon and get it into the crystalline matrix. Something like that I think. Not a metallurgist but I’m sure you guessed that! Would I get a decent hardened blade if I got it to temp and held for about 30 seconds and quenched?
 
Here you go. Pardon the disrepair, I haven't had to use this in a while. The end with giant screw through it is so I can get the blade out (I use tongs to grasp the screw and pull out the plug). It also has a small hole through which the thermocouple goes. The pipe is just 3 inch round pipe, but you can use whatever fits in your forge. I have top mounted burners so I left the uninsulated area at the 12 o'clock position on the pipe.

https://photos.app.goo.gl/9HerA8AfHaSGmb668
 
MBB, thanks for the additional info and pictures. I think I’ll go with the steel bucket for now as the smaller volume will be easier to heat (for me at least). I will have to look up how much oil a .50 cal ammo can can hold. It really sure how much quench oil I’d need for my blades. The ones I’m working on are 3/16” thick x 2” wide x ~11” overall long. Although I like the mortar box over a bucket as they use less floor space!
 
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MDelConte said:
MBB, thanks for the additional info and pictures. I think I’ll go with the steel bucket for now as the smaller volume will be easier to heat (for me at least). I will have to look up how much oil a .50 cal ammo can can hold. It really sure how much quench oil I’d need for my blades. The ones I’m working on are 3/16” thick x 2” wide x ~11” overall long. Although I like the mortar box over a bucket as they use less floor space!
Click to expand...

More oil = more quenches before you have to let the oil cool. May also improve your quenches if you do the "slice through the liquid with the quenched blade" approach.
 
I recommend two gallons or more quench oil. A gallon is OK for a small blade, but the more oil, the bigger the tank and the better it quenches. I move my blades up and down only in quenching. A good tank is 18" by 6", which holds about 2 gallons. The tank should be at least 6" longer than any blade you will quench and be at least 2" from any part of the blade in diameter. If you weld up a tank from pipe and a round/square base plate, make the base plate twice the pipe diameter for stability. Weld handles on each side of the tank about 3" from the top. Make a metal lid with a handle on it for the tank (nothing fancy, just a round/square plate that is an inch or so larger than the tank top).
 
MBB said:
More oil = more quenches before you have to let the oil cool. May also improve your quenches if you do the "slice through the liquid with the quenched blade" approach.
Click to expand...
Definitely. Have read not to go side to side and just do the slicing motion. Less prone to warping the blade. Tried to keep a dimes thickness on the edge but may be thinner in places. The stock is 3/16 though so I wonder if it’s even an issue.
 
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