If you've recently purchased some forged steel throwing knives, you may be dismayed to see scratches or even small dings in the blade after throwing it at a hardwood target. Tempering your blade can strengthen and harden it but may seem too complicated a process for you to tackle yourself. Fortunately, most steel knives can be tempered with materials you have around the garage (plus a few extras) and a free afternoon to tinker with them. Read on to learn more about tempering your throwing knives using just an oven and a few tools.
What are the benefits of tempering throwing knives?
Tempering your throwing knives can significantly extend their lifespan, making them more resistant to the normal wear and tear throwing knives go through. Many carbon-based knives may have one blade edge that's much more brittle than the other, a bad quality in a throwing knife that may lodge into the target at any point on the blade. Tempering a custom-made knife can also help "seal" its pattern from damage, as the knife will be too hard to warp or bend even when striking objects at a high speed.
What will you need to temper your knives?
In order to successfully temper carbon steel knives, you'll need the following;
- A forge (to heat the knife up to an ultra-high temperature)
- Heat-proof tongs
- A set of oven mitts
- A kitchen oven
- A fireproof quenching container (like an old aluminum pan)
- A nonflammable quenching liquid like used motor oil, heated to bathwater temperature
- A small length of aluminum tubing
- A steel file
Once you've assembled your materials, you're ready to begin!
Where should you start?
Although it can seem more efficient to temper multiple knives at once, those who haven't tried this before will generally want to temper throwing knives one at a time. Before you temper your knife, you'll want to prepare it by ironing out any defects (except the ones you'd like to keep) and filing the blade edges to dull them a bit. An ultra-sharp blade runs a greater risk of shattering during the tempering process, and the last thing you want to do is end up with a jagged-edged knife that quickly tears holes in all your targets.
Next, you'll want to pour the quenching liquid into the quenching container, setting the tongs next to it -- once you've used the forge to heat the knife until it's literally red hot, you'll need to quickly submerge the entire blade in the quenching liquid. Be careful during this part, as the blade can be incredibly hot and dropping it or hitting it against something is certain to shatter the blade into bits. In order to determine whether your blade has reached its critical temperature, place a magnet near it. Heated steel loses its magnetic qualities, so if the magnet doesn't have any attraction toward your knife, it's likely warm enough to quench.
Once the quenching oil has stopped bubbling, your knife has likely spent long enough in its oil bath. Remove it with the tongs and take it to a bench where you can gently run a steel file over its surface. Any rough patches or other defects should be smoothed out at this time, while the steel is still pliable and before it has been oven-tempered and is much more difficult to modify.
You'll then want to heat your oven to a temperature between 300 and 400 degrees. It's possible to temper your quenched steel at lower temperatures than this, but it won't be as effective at increasing its hardness. Baking your knife for about 20 minutes should finish the process, giving you a hardened steel knife perfect for target practice.