[7 Key Facts] How to Harden and Temper a Knife? (Knife Knowledge)
It is difficult to tell if a knife has been properly heat-treated by simply looking at it. The contrast between the knife’s surface and heat treatment can be determined by using it continuously. Heat treatment is essential for a knife to be able to perform at its best at the task at hand.
You should research the steel you are going to use before heat treating it. Each steel is different and each has its own heat treatment process. To maximize the steel’s potential, it is a good idea to identify and follow the recommended procedure.
Tips Before You Harden
The next step in the blade-making process is hardening. However, working with hardened steel can be more difficult. There’s another round of grinding after hardening. Make sure you have removed any impurities from your blade while it is still soft. Drill holes in your tang as soon as possible to attach the scales later with pins. To fully secure the full-tang knife’s scales, epoxy is used in addition to pins. Pins are used to ensure that epoxy bonds can withstand any shear force and strengthen scales. Pins make attachment much easier by guiding the scales. Your personal preference and the look you prefer for your knife will determine which holes you choose to place on your handle. You can also decide the pins’ diameter you will use. Make sure the hole you drill is the same size as the pins, or slightly larger. You can use your grinder to reduce the pins’ diameter if you make a mistake when drilling. If your handle and blade are not balanced, you can make your tang skeletonized by drilling some extra holes in your tang.
A gap at the handle of bushcraft knives is often used to attach a lanyard or rope to your knife. This hole can be made optionally, or you can use a drill to make it.
A jimping can be added to your knife. A jimping is an assortment of The spine has notches near the handle. These are added grips for precise movements, such as detailing. You should space them evenly and keep them parallel to the edge of your blade. You will need a power tool and a Dremel to create one. Next, use sandpaper to fill e the edges. This can be a difficult task, so make sure the blade is securely secured before you begin.
Be sure to check your blade for any weak points before you harden it. There are three key factors to heat -treatment: heating, cooling, and time. You need to know how to combine these three factors in order for your steel of choice.
Hardening is the first step in heat-treating. This is done by heating the steel to a high temperature and then cooling it down quickly. While steel that has just been annealed is soft and can be used, it will harden after hardening. It is important to harden your blade in order to keep its edge. To prevent your blade’s steel from becoming too hot during hardening, please pay attention to every part. This could cause damage to your blade and can make it difficult to enjoy the fruits of your labor.
Steel can also become too fragile during hardening. Temper your hardened blade with extreme care. Dropping hardened steel can cause it to shatter like glass. If you don’t have time to temper the knife immediately after, never harden it.
You don’t need a forge to harden your knife. Instead, make a firepit and heat it. This produces the same results that a forge does, but you can easily monitor your knife during hardening. It is easier to check with a magnet because you can pull the blade out of the pit. You will need bricks or rocks to make a firepit. Place them in a circle so the fire doesn’t spread. If an accident does occur, make sure you have a water source nearby. Hardwood charcoal is better than regular firewood because it will heat up quickly.
To create an air source for the pit, attach a steel pipe to a hairdryer. The steel pipe should be placed in the middle of the charcoal.
The steel’s temperature can be quickly brought down to room temperature by quenching. Slow cooling does not allow the steel’s microscopic structure to undergo further changes, so quenching is a better option. Your steel will become harder the faster you quench it. However, this can pose a danger to your steel because a fast quench could crack or deform your steel. The steel will not fully harden if the quenching process is too slow.
Every steel has its own requirements for quenching. This is why you need to research the steel type you intend to use first. The cooling rate will depend on the agent used to quench. Water is a good medium for quenching. You can also use commercial oil quenchants for quenching. You can also use Canola oil, or a can motor oil as an alternative. Preheated oil can quickly disperse heat, and it is less stressful for steel.
You should be prepared for any accidental fires that might occur when you heat your steel in the oil. You can prevent fires by completely submerging the steel in the oil. To cut out oxygen, prepare a fireproof lid to place on the flames. Water is not recommended for extinguishing a fire as it can spread the oil. To avoid injury, always use your safety equipment to quench your blade.
The Hardening Process
Start your forge, or add a good amount of coal to the pit. Then start your fire. As you heat your blade, make sure there is enough coal to keep it going. You should keep an eye on the fire and add charcoal as soon as possible to ensure that it doesn’t go out.
The blade should be placed in the middle of the fire. If you are using a pit, place it where the air meets the charcoal. To ensure that your blade doesn’t heat up, align the tip of the blade away from the hot spot. Keep in mind that your blade’s edge and tip are the most delicate parts of your knife. You should take extra care not to damage these areas.
Move the blade around the fire and observe the consistency of the steel. This will help spread the heat evenly across your blade. Do not worry about heating your Tang.
Your blade’s overall performance will be affected.
Similar to forging, you’ll need to constantly monitor the temperature of the blade. You can use the same technique as when forging, either using a thermometer (or a magnet). The steel that is forged with a magnet will lose its magnetic properties around 774degC. This will mean you have reached your desired heat. After the steel loses its magnetism, heat the blade for about twenty seconds more. Then remove it from the fire.
Once you have removed your blade, submerge it in the oil. To cool the blade quickly and prevent it from hardening, move the oil around. You can reduce the risk of your blade becoming bent by moving it from the spine towards the edge, rather than from any other direction.
After the blade has cooled, take it out of the quench. Use a file to move the edge of your blade across its side to check if hardening has been successful. The file should be able to move freely throughout the blade, without having to dig in. If the surface is scratched it may mean that the blade has not reached its maximum heat and will need to be heated again.
After hardening your blade, cool it to room temperature. Then wash the oil off with soap and water. Next, temper your steel by heating it evenly at a temperature close to its critical temperature. The steel must cool down after being heated. This will allow the steel to fully temper and complete the heat-treatment process. After this, your blade’s edge should be durable and hardened.
For tempering, you will need an oven. For around 15 to 20 minutes, heat the oven to 204°C. This will stabilize the temperature and allow you to begin the tempering process.
The blade should be placed in the oven on the rack. Let the blade cool down after heating it. After cooling, return the knife to the oven to heat it up again. Some types of steel require additional heating cycles. Make sure you research what steel you are using before heating it again. After heating is complete, take the blade out from the oven and let it cool down again.
Grinding Round Two
It’s now time to grind the blade again after the heat treatment process. You will be using a water quench more frequently by this point, as it is important not to heat your steel on the grinder. To check if your blade is too hot, you may not need to wear gloves. If your steel starts changing color, it is an indicator that it has become too hot. If the color changes to blue, it is likely that your steel has been overheated.
After heat-treatment, scales can also build up on your blade. These can be removed with a rough belt. If you notice that the blade is heating up quickly and scales are still present, use files to remove them.
Once you have removed the scales, it is time to complete your bevel. It can be harder to use the blade after the steel has been hardened. This can take more time, but it is worth it. To create a sharp edge, complete your plunge lines. After you have removed the majority of the steel, switch to a finer belt for cleaning up.
Polishing is the last step in making your blade. Your blade will look great and create less friction. This allows you to make better cuts. Your blade will look ten times better if it is polished than a non-polished blade.
Do not forget to polish your tang as this will be a key part of your handle creation later. Attach scales to your Tang. A rough surface is more compatible with adhesives than a smooth surface. You should polish the knife’s exposed parts, especially the handle.
This section requires sandpaper that is specifically designed for sanding metals. Wet/dry sandpaper is a good option, especially for hard steel. Polishing your steel can be made easier by using oil such as WD-40 to lubricate it. This will help your sandpaper last longer, and can prevent binding or clogging.
Place your blade by the tang on a flat surface. Turn your face to the blade. Take note of your last grind lines. You can then start sanding at 45 degrees on these lines. This will allow you to distinguish between the finer, polished grinds and your earlier grinds. You’ll be moving from coarser sandpaper to a finer one. More polish than you polish. Focus on removing gridlines from the previous grits. Once you have removed these gridlines, you can switch to a finer grade grit and adjust your angle. To see the lines in your grinds clearly, make sure you have a good lining.
Continue polishing your blade until it reaches the desired level of polish. The final sharpening of the edge will take place later. To prevent any accidents, cover your blade with painter’s tape after you are done polishing.