Tempering of knives is the best way to get your knife soft and also tough at the same time. These are two contrasting but possible properties that should characterize a good knife. The action is very vital as it ensures your knife becomes harder. However, if not done in the right way, it can also make your favorite blade brittle like glass, causing it to shatter when not handled properly.
As a result, it is vital to know how to temper a knife rightly; so, you don’t end up causing more harm than good. Do you have to be a professional to do this correctly? No, you don’t. I guarantee that after reading this article, you will be able to temper a blade like a pro.
What Does Knife Tempering?
Knife tempering is the process of treating knives with heat, between the temperature range of 347°F-662°F for about 2 hours. It is done to iron-based alloys toughness and follows after hardening of the knives has been carried out. The goal is to give it a hardness between 53-63 HRC making it flexible, while it also ensures it’s not so brittle that it shatters upon hard impact.
It is crucial to know that the temperature determines the percentage of hardness removed from the knife. When done at a high temperature (650°F), you get a soft blade that is also tough, while at a low temperature (375°F), you get a blade that is hard and also has a sharp edge. Therefore, depending on what you need the knife for, you’ll need to consider what temperature you need to temper your knife.
Steps on How To Temper A Knife
Having looked at what knife tempering means, I’m sure you would have realized that it is essential to get the temperature right to ensure you get your desired finished product. That is, you don’t want to get a soft knife when you plan on achieving a hard one and vice versa. So, what is the best way step-wise method to tamper your blade?
Step 1: Prepare Your Knife
The first step is to prepare your blade for the processes yet to come. To do this, you need to first get rid of left-over carbon buildup on your knife. To do this, you need sandpaper of about 180grit. This would be used for flat sanding the edge of the blade. This is done to dull it and also prevent it from warping or cracking. Next, you’ll need to remove excess chemicals with the use of a rag containing acetone. This process completely strips the knife of any left-over residue.
Step 2: Stabilize The Steel Structure
This is the next step; the process is generally referred to as normalizing. It entails stabilizing the steel structure by bringing the blade (unhardened) a few times to a critical temperature. The aim is to change the structure of the knife, making it tough and ductile. This way, the blade possesses greater resistance to warping when it is time to quench the knife. To do this, pass the knife across even heat, then use a magnet to check if it is at a critical temperature (at this temperature, the knife would become non-magnetic), allow it to cool back to room temperature. Repeat this process three times to enforce normalizing.
You can use a kitchen oven or even a toaster oven to carry this out if you don’t have access to a forge, and even heat is distributed around the knife. It is best to leave it in the oven for an hour each time before you test against the magnet.
Step 3: Quenching
Before you get to this step, be sure you have the right tools to carry this out successfully. You’ll need a set of pliers and a container with a lid. The container is for quenching and must be fireproof, avoid using plastic or anything that can meltdown due to the temperature of the knife. You also need a lid that is airtight to ensure the container can smother the flames.
First, fill this container with enough water and then mark the water level using a colored marker, taking note of the point where your knife would rest. You also need a regulator block and nails to mark the position of the block placed below the oil level. This will reduce the risks of warping as a result of one side cooling faster than the other side cools.
The oil is used to quench and should therefore contain qualities that make this process easy. You can check this out by warming it up. You can also determine the exact temperature you would be needing for this by heating the water placed in the container. It is also vital you get a fire extinguisher (BC) nearby to handle unplanned events.
After normalizing, put your blade back to the oven/forge, heat it again evenly, and then gradually submerge it into the oil in the quenching container. Ensure you do this in such a way that the oil does not splash out of the quenching container while making sure your knife does not lose significant heat. Then immerse it on top of the regulator block and leave it for about 15sec. Next, submerge it into the oil again. Wait for the oil to stop hissing and bubbling (about 45 secs later), and then remove the knife from the oil and leave it to cool in the open air. Then place the lid on top of the quenching container to ensure flames are smothered.
Note: you can check if this process worked well using a file placed on the knife’s bevel. Move the file up-and-down, back-and-forth, along the length. If the file feels glassy, then you’re good to move to the next step.
Step 4: Tempering the blade
It is advised you temper your knife outside your kitchen to avoid smoking the kitchen with residue oil in the oven. So, avoid a Kitchen oven if possible and stick to a toaster oven if you can’t afford to use an outdoor forge. However, if a kitchen oven is what you have, then end=sure you first get rid of the excess oil by using dish soap. This should get rid of the smoky oil smell.
First, determine the type of iron-based alloy your knife is made of and then determine the right temperature for tempering; you can find this information online. Heat your knife at the right verified temperature for about an hour, leave it to cool back to room temperature, and then place it back to heat up for an hour again. Repeat this process thrice to get a good-tempered knife that meets your specifications.
Step 5: Final Sanding Process
At the end of the day, you need to repeat step one to get rid of any oil residue or buildup that likely occurred as you went through the various processes above. However, in this step, we’ll start by using a stone of 220 grit or lower depending on what you have. Then we’ll switch to a larger gritstone until you get the desired edge that suits your taste. This would smoothen and ensure the knife retains its edge. After this is done, then your tempered knife is ready for your use (in the kitchen or outside the kitchen).
Tempering a knife is a skill everyone should know about, as well as its benefits, and how it can ensure your knife meets your various needs. However, unless you are aware of the process, you can end up doing the wrong thing, and hence damage your knife.
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Consequently, a comprehensive guide on how to temper a knife is crucial to ensure everyone knows the proper steps to take when they want to temper their knife. So, the next time you need to temper your blade, do not hesitate to DIY using this as a guide and let us know when you do; we would love to hear how the experience was for you.