Heat treating knives is an integral part of the knifemaking process. After designing the knife, cutting the profile, and adding the bevel, heat treating knives is one of the final stages of knifemaking before finishing the blades and attaching the handle.
What Is the Purpose of Heat Treating Knives?
Knifemakers expose blades to specific temperatures (or setpoints) for specific time intervals in order to imbue their blades with specific qualities. This process is known as heat treating. Heat treating changes the molecular structure of the metal or alloy, allowing knifemakers to adjust the following qualities for their blade:
- Hardness: The blade’s ability to hold sharpness and withstand abrasion.
- Ductility: The blade’s ability to ‘bend but not break.’
- Material Strength: The blade’s ability to resist deformation and withstand stress without fracturing.
- Toughness: A combination of ductility and strength, basically measuring a blade’s overall resistance to damage from external forces.
- Malleability: The ability to work the blade and alter its shape.
- Temperature Resistance: The blade’s ability to withstand temperature, as well as its susceptibility to corrosion at higher temperatures.
- Magnetism: Whether the blade does or doesn’t exhibit magnetism (if you’ve ever had kitchen knives you can store on a magnetic strip, heat treating is why!).
Depending on application, knifemakers will want their knife blade – or even different layers of the same blade – to have different properties. Therefore, heat treating knives usually occurs in multiple stages to alter different properties, which we’ll be covering in more depth below.
Equipment You’ll Need for Heat Treating Knives
Before heat treating knives, you’ll need to have the proper equipment. Knifemaking is one of humanity’s most ancient tool making processes, with heat treatment being introduced to the medium during the Bronze Age in 3300 BC.
Of course, heat treating knives can be done with extremely rudimentary setups – such as using a charcoal forge or a propane torch! But, for the purpose of this guide, we’ll be writing for the modern artist and assuming you’re using an electric heat treat oven.
- Heat Treat Oven or Knife Kiln: You’ll need a knife kiln or heat treat oven that’s big enough to accommodate the blade and capable of reaching the right temperatures.
- Heat Treat Oven Controller: You’ll need a heat treat oven controller in order to manage the temperature of your heat treat oven – your controller can be a single setpoint controller or an advanced multi-setpoint controller.
- Finished Knife Blade: Heat treating knives hardens them and makes them less workable, so you’ll want to cut your blade and give it your preferred finish prior to heat treating. Knives can be made from a variety of metals and alloys, ranging from uber-versatile options like 1095 steel to more specialized, premium (and expensive) options like CPM S110V.
- Vise Grip or Tongs: When heat treating knives, you will need to be able to transport the blade while it’s still extremely hot from the oven to the quenching medium.
- Quenching Medium: You will need a quenching medium – such as oil, a salt-water solution, or sand – in which to cool the knife blade. (Oil is by far the preferred medium for knives, which we’ll cover in more depth below).
- Quenching Container: You’ll also need a fireproof quenching container in which to hold the quenching medium.
- Tempering Oven: You will need an oven, set at a lower temperature, in which to temper the knife. It may take too long for your primary heat treat oven to cool down enough to use for tempering, so many knifemakers use a dedicated tempering oven or even their kitchen oven (our partners at Evenheat offer a really cool stackable configuration that combines a knifemaking kiln with a tempering oven!).
- Fire Extinguisher: Any time you’re working with high temperatures, kiln safety precautions are key. Keeping a reliable fire extinguisher near your oven can help protect your property, as well as your personal wellbeing.
- Protective Equipment: Additionally, you’ll want protective equipment such as heat resistant gloves and a face shield or safety glasses for safely handing your blade and managing your oven at high temperatures.
- Knife File: You will need a file in order to test the hardness of your blade after heat treat.
- Sandpaper: After heat treating your knife, you’ll need to finish it a final time to remove the black coloring from quenching. For this, you’ll want to start with a coarse grit and finish with a smoother grit.
- Knife Sharpening Stone or Belt Sander: Finally, you’ll need a knife sharpening stone or belt sander to sharpen your finished knife so that it’s ready for use!
10 Steps for Making Knives
As we mentioned at the beginning of this article, heat treating knives is one of the last steps in the knifemaking process. Since heat treating knives makes them harder and less workable, most of the steps in the knifemaking process will need to be done prior to heat treat. Just like with baking a cake, you want to get everything right before placing it in the oven!
Below are the general steps for knifemaking:
Step 1: Designing Your Knife
Before starting work on your knife, you’ll need a design. For your design, the more detailed, the better! You will want to consider the shape of the blade, the correct bevel, the kind of finish you’ll want, and the type of handle you’ll be using.
While many knifemakers use pen and paper to sketch their knives, you can also find tons of free templates online such as these free knife templates from D. Comeau Custom Knives.
Step 2: Selecting Your Steel Alloy
There are a variety of different steel alloys that can be used for knifemaking. Alloys containing different elements have different properties, so it’s important to consider what your knife will be used for. For instance, with kitchen cutlery, you’ll most likely want to use stainless steel and may prioritize exceptional sharpness over toughness. For a more general-purpose knife, options like 1095 steel are easy to work with, widely available, inexpensive, can hold a very sharp blade, and exhibit good toughness – but they are susceptible to rust.
At the end of the day, there will always be some sort of tradeoff, so it’s about selecting the steel alloy that provides the most benefits and the fewest cons for what you’ll be using your knife for.
Step 3: Cutting the Blade Profile
As we mentioned earlier, you’ll want to get your blade as close to its final shape as possible before heat treatment. Before cutting your blade, use a marker or sharp tool to draw the outline of the knife blade onto the steel. Then, use a hacksaw to get close to the final shape, while still leaving slight margins around the edge.
From there, place your blade into a set of vice grips and use a blade file to clean up the edges, until you have the intended profile. At this stage, it’s better to move slowly and methodically – you can always remove excess material, but you can’t add it back if you cut or file too far!
Step 4: Beveling Your Blade
A knife bevel is the point where the body of your knife begins angling into the edge of the blade. You will want to define this transition point prior to heat treatment. To bevel your blade, use a marker or sharp object to denote where the bevel begins and use a file or sander to slowly define the angle to the blade’s edge. Start by beveling one side of your knife, and then do the other – keeping your angle as steady and consistent throughout as possible.
Step 5: Drilling Your Blade
After heat treating knives, you’ll need to attach the handle. Prior to heat treat, you will want to drill the holes in the blade profile where you’ll use pins or rivets to secure the handle later. The number and placements of these holes may vary depending on the type of handle you’re using, as well as how you’ll be using the knife – but the important thing is making sure that the holes in the blade profile match up evenly with the holes in the handle (and to drill the handle before heat treat – unless you want to blow through carbide bits with little luck!).
In the video below, Walter Sorrells provides a walkthrough for fashioning a jig to ensure the holes you drill in both the blade and the handle match up every time:
Step 6: Finishing Your Blade (Prior to Heat Treat)
We’ve said it before, but just to reiterate: Your knife will be far more easily workable prior to heat treat. As much as possible, you’ll want to get your knife as close to its final form as possible before putting it in the oven – and that includes giving it the correct finish! To finish your blade, you will use rough grade sandpaper to smooth out any marks or irregularities. Then you’ll use a finer grade sandpaper to fully polish your blade.
This will also be the opportunity to apply any textures or effects to your blade if you’re going for more artistic effects.
Step 7: Heat Treating Your Knife
Finally, now it’s time to heat treat your knife! While we’ll be covering heat treating knives more in-depth in the sections below, at minimum heat treating knives requires at least two processes:
- Hardening: The metal is heated and then cooled to increase its hardness. There are several different types of hardening used in heat treatment, but quench hardening, where the metal is heated and then rapidly cooled in a quenching medium, is by far the most common for knives.
- Tempering: After hardening, the metal is heated to a lower temperature for a longer period of time to reduce excessive hardness and relieve internal stress, reducing brittleness.
The general goal of heat treating knives is to have a blade that’s hard enough to cut the necessary materials, without being so brittle that it’ll break under pressure. But some knifemakers will have more specific requirements for their blades that may require additional, or more specific, processes.
For each metal, there is a unique setpoint and hold time for both hardening and tempering. Using an advanced heat treat controller such as TAP II, TAP II Pro, or the recently released TAP&Go Single Setpoint Heat Treat Controller from SDS Industries allows heat treat artists to precisely program their heat treat oven to reach the exact setpoints and hold times they need.
The heat treat controllers in the TAP Ecosystem also have additional benefits for knifemakers that ensure consistency, save time, and maximize efficiency, such as:
- The ability to save an unlimited number of different firing schedules – so that you can select the exact schedule you need for each alloy and process without ever having to recreate them.
- The highest possible precision and accuracy through PID-driven control algorithms for maximum consistency.
- Remote temperature monitoring and real-time alerts via the TAP Kiln Control Mobile app so that you are always fully aware of the progression of your heat treatment.
- Premium TAP Kiln Control Mobile features like Remote Start lets you get your oven heated up remotely which can help you multitask more effectively.
Step 8: Re-Finishing Your Blade
After quenching, your blade profile will likely be discolored and darkened from the quenching oil. Now that heat treating is complete, it’s time to put on the finishing touches. You’ll need to finish your blade once again. This process will be very similar to finishing your knife prior to heat treating. First, you’ll start with a coarser grade sandpaper to remove the discoloration, followed by a finer grade sandpaper to give it its finishing sheen.
Step 9: Attaching Your Handle
Remember the holes you drilled into your blade profile in Step 5? Now you’ll use those holes to attach the handle to your knife! You will need to insert pins or rivets through the holes in your blade profile and through corresponding holes drilled into your handle. And then you’ll use epoxy to securely fasten the handle to the blade.
Once the multiple layers are securely attached, you may need to finish cutting and sanding your handle to ensure a one-to-one match.
Step 10: Sharpening Your Blade
Finally, the last step in making a knife is to sharpen your blade. With the bevel already defined, you will only need to focus on the edge of the blade. Here you can use a knife sharpening stone or an electric belt grinder. Just make sure to alternate between sides until your blade is sufficiently sharpened.
Also, be sure to be mindful of heat transfer from your knife’s edge – especially if you’re using a belt sharpener. This is when you produce so much friction that it causes your knife to heat up so much that it starts to deform or lose its sharpness. To prevent this, do quick, light passes where you don’t hold the knife to the belt for prolonged periods of time.
Additionally, sprinkling water over the knife’s edge during sharpening can help prevent this.
Processes for Heat Treating Knives
Now that we’ve looked at the role of heat treat within the knifemaking process, we want to zoom in on the specific processes used for heat treating knives. As we mentioned earlier, there isn’t a one-size-fits-all process when it comes to heat treating knives. The purpose of this section is to give you an overview of the different types of processes so that you can choose the ones that are right for you!
From there, you’ll be able to research the critical temperatures of the type of steel alloy you’re using for your blade. We encourage you to check out Facebook groups, YouTube, and Reddit and reach out to other knifemakers if you’re trying to accomplish something more specific for your blade. The heat treat community is vast and extremely helpful, and you can save a lot of time by benefitting from other knifemakers’ knowledge.
Normalizing
Normalizing relieves internal stress in your knife, reduces grain size, and ensures uniformity. The result will be a harder, stronger blade. To normalize your blade, you will heat it to extremely high temperatures for a pre-defined period of time – and then allow it to air cool. Knifemakers often repeat this cycle several times.
Below is a normalizing schedule for 1095 steel:
After the 15-minute hold time has been reached, remove your blade from the oven and allow it to fully air cool before repeating the cycle again if necessary.
Annealing
Annealing your knife can have several benefits. Firstly, it can be used to make your blade profile more workable, which makes it easier to make adjustments to your blade. Additionally, annealing can be used to increase the overall ductility and toughness of your blade.
To anneal your knife blade, heat it up to the critical temperature and then allow it to slowly cool at a controlled rate. Since you don’t need to maintain the critical temperature during the first part of quenching, you don’t need to heat your blade to as high a temperature as you would for normalizing or quench hardening.
So ,for 1095 steel, the annealing setpoint would be 1475°F. Once the blade has reached this temperature it would need to be cooled at a rate of 50°F or slower until it reaches 1200° F, at which point your blade can be air-cooled.
In order to achieve this specific ramp rate on the cool down, knifemakers often use their furnace and a programmable digital kiln controller to cool the blade at a controlled rate.
Quench Hardening
Although there are multiple types of hardening processes, quench hardening is by far the most common type used for heat treating knives. Other processes, such as case hardening – which only hardens the outside of a blade – aren’t really applicable on such a small blade and are common for swords, battle axes, or other larger blades.
Quench hardening your knife involves a similar firing schedule to normalizing – the big difference is the rate at which you cool down your knife after bringing it to temperature.
As you can see, you heat the blade above the upper critical temperature, but when you remove your knife from your oven, instead of letting it air dry, you submerge your blade in quenching medium until it cools down to 150°F. You can purchase dedicated quenching oils which cool at specified ramp rates, but many knifemakers also use peanut oil, canola oil, or motor oil. Sometimes water is used, but this often causes the knife to cool very quickly, resulting in a very hard, but extremely brittle knife.
The important thing is to use a quenching medium that cools your knife down fast enough to give it sufficient hardness, but not so fast that it jeopardizes its structural integrity.
Tempering
After quench hardening, your knife will be harder, but also more brittle than it was prior to heat treat. If you think about the practical applications of a knife, you need the blade to have enough give so that it doesn’t shatter or fracture when you apply pressure to it. That’s where tempering comes into play!
Tempering your knife will reduce excessive hardness and relieve internal stress, resulting in a more resilient blade.
To temper your knife, you will place it in an oven for a prolonged hold time at a significantly lower temperature than you used during hardening. Some knifemakers use their kitchen oven, but you can also do this in a dedicated tempering oven.
Below is a tempering schedule for 1095 steel:
The important thing is to temper your blade shortly after it cools from quench hardening – within 30 minutes to a maximum of 2 hours. After tempering, you can allow your knife to cool within the oven or air cool – and you’ll have a blade that’s hard but not too brittle!
Explore TAP Heat Treat Controllers by SDS Industries
Are you looking for a heat treat controller that provides more precision and convenience for heat treating knives and smithing blades? TAP by SDS Industries has got you covered!
The TAP II and TAP II Pro Controllers by SDS Industries provide advanced, precise, and easy-to-use multi-setpoint controls for your heat treat oven. These controllers offer responsive controls and an intuitive graphical UI on a large, easy-to-read touchscreen, allowing you specify ramp rates and hold times for each step for maximum convenience.
Our new TAP&Go is a single setpoint controller designed specifically for heat treat. With simplified controls and a more affordable price point, TAP&Go provides the fundamental functionality most knifemakers need!
All of the TAP Controllers are compatible with any relay-controlled kiln or oven and integrate with the TAP Kiln Control Mobile app to maximize your productivity while always keeping you informed on the status of your oven.
We invite you to explore our selection of programmable kiln controllers, standalones, and conversion kits on our online store. You can also purchase TAP Digital Controllers or TAP Controlled Kilns and Heat Treat Ovens through one of the following distributors:
- Evenheat
- Hot Shot Oven & Kiln
- Paragon Kilns
- Mobile Glassblowing Studios, LLC
- Jen-Ken Kilns
- Kiln Frog
- Sheffield Pottery
- Delphi Glass
Knife Heat Treating FAQ
What temperature will my oven need to reach for heat treating knives?
To effectively heat treat blades or knives, you’ll need a heat treat oven that’s large enough to accommodate your blade and capable of reaching the right firing temperatures.
But how do you know the right knife heat treating temperature? That all comes down to the alloy you’re using for your knife or blade.
There are three important setpoint temperatures you’ll need to keep in mind:
- Critical Temperature: This represents the maximum temperature you’ll need your oven to reach for normalizing or quench hardening.
- Annealing Setpoint: This is a slightly lower temperature through which your knife blade needs to be slowly cooled before being allowed to air cool during annealing.
- Tempering Setpoint: This is a drastically lower temperature that you will need to heat your knife blade to in order reduce excessive hardness and relieve internal stress.
Knife Heat Treating Temperatures
Each of these setpoints will change based on the alloy you’re using. Below are critical temperatures for common alloys used in knifemaking:
- 1084 Steel: 1600°F (871°C)
- 1095 Steel: 1600°F (871°C)
- 80crv2 Blade Steel: 1650°F (899°C)
- C1500 Copper: 1796°F (980°C)
- A2 Medium Alloy Steel: 1800°F (982°C)
- A6 High Carbon Steel: 1875°F (1024°C)
- Stainless Steel: 1900°F (1038°C)
- T2 Tungsten High Speed Steel: 2375°F (1302°C)
To work with any of these alloys, you’ll need to ensure that your heat treat oven is capable of firing to the temperatures above! Then, be sure to look up the annealing and tempering setpoints for your specific alloy.
How do I sharpen blades after heat treating?
After heat treating your knife, the blade will be far harder and less workable than before. So, you’ll want to make sure you have your bevel defined, your holes drilled, and your shape fully defined before heat treatment.
But, by the same token, if you try to sharpen your blade before heat treatment, the steel will be too soft to hold an edge – and you’ll risk accidentally shaving off material you didn’t mean to.
So, you’ll want to wait until after heat treat to sharpen your blade. You can make sure your knife is as sharp as you need it to be by following these steps:
How to Sharpen a Knife After Heat Treating: Sharpening Stone
First, we’ll look at how to sharpen a knife after heat treating using a knife sharpening stone. This is one of the most popular methods of knife sharpening for a few reasons: It gives you more control, it’s harder to mess up, it’s more affordable, and it gives you the hands-on, tactile experience that many knifemakers and bladesmiths appreciate.
Plus, this method drastically reduces the chances of heat transfer from friction deforming your edge (but that’s still something you’ll want to be mindful to avoid). You can sharpen a knife with a sharpening stone by following these steps:
- Prepare Your Knife Sharpening Stone: Depending on the type of stone you’re using, you’ll typically need to lubricate it with water or oil (unless you have a specialty stone you can use dry). Sometimes this involves completely soaking your whetstone. Make sure to follow manufacturer instructions – and take the time to be sure your stone is completely free from debris that can damage your blade.
- Place Your Sharpening Stone on a Slip-Free Surface with the Coarse Side Up: You won’t be able to generate the friction you need to sharpen your blade if your sharpening stone is sliding all over the place. Place your stone on a surface like a wet towel, rubber mat, or between vice grips to keep it firmly in place. You will want to start with the coarse side facing up.
- Hold Your Blade at 20° from the Sharpening Stone: If that angle sounds overly specific, don’t worry! Hold your knife blade-down against the whetstone so that it’s completely perpendicular. That’s 90°. Tilt your blade closer to the sharpening stone to halve that distance. You’re at 45°. Tilt your blade again to halve the remaining distance, and you’re at 22.5°. Just a touch beyond that, and you’re ready to start sharpening!
- Flip Your Blade to Sharpen the Other Side: When you notice a burr develop, flip your blade over to start sharpening the opposite side to balance out the edge of your blade.
- Repeat Steps 4 and 5, Regularly Alternating Sides: Repeat Steps 4 & 5, regularly alternating sides to ensure uniformity, balance, and sharpness. If you feel your blade heating up, take a quick break – and regularly relubricate your whetstone as necessary.
- Refine Your Blade: Once your blade is sufficiently sharp, use the finer side of your sharpening stone, a leather strop, or both, to polish out any rough edges. Again, make sure to alternate sides so that your edge is perfectly centered.
Now, your heat treated knife is sharp and ready for whatever job you throw at it!
How to Sharpen a Knife After Heat Treating: Belt Grinder
Using an electric knife sharpener is the quick and easy way to sharpen your knife after heat treating – but you’ll have to be mindful that your edge doesn’t get too hot!
Just like with a sharpening stone, you’ll hold your blade at approximately 20°, applying gentle pressure against the grinder, and regularly alternating sides at equal intervals.
If you notice your blade warming up, apply water or oil to cool it down – or take a break to let it cool down.
Regardless of which method you choose, make sure to regularly sharpen your knife blade to protect its integrity.
What type of oven controller do I need for heat treating knives?
Choosing the right type of oven controller can make a major difference on your heat treating experience. Different types of controllers provide different levels of precision, versatility, and ease of use.
Knifemakers can usually get by with a single setpoint controller since most cooling processes for heat treat occur outside the oven. However, a fully featured multi-setpoint controller adds additional levels of convenience and precision – especially for controlled annealing.
Regardless of whether you choose a single setpoint or multi-setpoint controller, SDS Industries has you covered! Last year, our partners at Evenheat conducted a study about customer buying habits. When shopping for heat treat ovens, they found that – when given a choice between TAP and the competition – 80% of heat treat artists choose TAP.
That’s because TAP provides a host of benefits that help knifemakers and bladesmiths make better blades. Benefits include:
- PID Precision: Our PID oven control algorithms ensure your ovens get as close to your programmed setpoints as physically possible.
- Simple Controls: In a heat treat environment, you don’t have time to fumble with keys. Our intuitive touchscreen controls help you program your oven faster and reduce user error – even when using gloves.
- Unlimited Schedules: TAP lets you create, save, and execute unlimited firing schedules – so all of your setpoints for all of your alloys are only ever a few finger presses away.
- Remote Monitoring & Control: All of our controllers let you remotely monitor your oven – with real-time push notifications alerts and alarms – through TAP Kiln Control Mobile. You can even remotely start firings, abort firings, or make adjustments on the fly!
- Advanced Diagnostics: Advanced diagnostics and preventative maintenance alerts help you maximize uptime, enhance oven safety, and accurately price work.
These features help you multitask more effectively, operate more efficiently, and improve the quality of your projects.
And that’s just scratching the surface. We invite you to explore the TAP Ecosystem to find the perfect heat treating controller for your knifemaking adventures!
