It’s Not How Sharp It Goes In
That Matters, It’s How Sharp It
Comes Out
At R.A.D. Inc. when we set out to design a broadhead the blades are the first thing we look at. They control almost everything from flight, penetration, and speed of kill. Vent shape, trailing edge shape, diameter, thickness, grind, hone, heat-treat and material all come into effect. Everything revolves around the blade. And here at R.A.D. it remains the leading feature.
Everything in a blade is interrelated. You want them to fly true, but only if they are stout enough to hold up against the target and sharp enough to finish the job at hand. And most important is maintaining that sharpness through the target.
Flight
Flight is a relatively easy thing to design. You reduce the effect of wind, rain, and updrafts with straight sloping edges. You keep vents to a minimum while maintaining the chosen effect. And again, watch the size of those edges. Many ask us how we fly better than “X expandable” or “X manufacturer” In most circumstances today it has to do with trailing/vent edges. For the most part if you reduce friction, you improve flight. Solid blades, within today’s size, are great fliers too. In most cases outperforming vented models.
Durability
Durability like flight has a lot to do with edges and vents too. Vents and edges need to be shaped to minimize stress, noise, and shear. Solid blades shine when durability comes to bare. The thickness of the material is a big factor too. Too thin and it’s easier to fly, sharpen and penetrate, but it tends to fracture or must be made soft. Too thick and weight is hard to achieve, sharpness is hard to achieve and flight and penetration suffer greatly. A softer blade is often used to add durability; however, this rarely gives you what you are looking for as far as killing the animal.
Penetration/Noise
Penetration/Noise are pretty much the same. What makes noise from air will conflict with tissue also. This affects the front of the blade as well as the internal and rear of the blade. A straight sweeping back edge, a solid or small properly designed vent, blade thickness and sharpness are all carefully employed to avoid problems with noise and penetration. Sometimes a level of compromise must be used, but the properties that affect it are always the same.
Sharpness
Sharpness is the final and most important step in this interrelated challenge. For when the flight is true, the durability maintained, when noise reduced and the arrow finds the proper home, it’s how sharp it enters and more yet, how sharp it EXITS that matters most.
Stainless Steel
Stainless used in most hunting blades today have come a long way. In its original form stainless was a terrible blade material. Heat-treat had to be very soft or it reached a glass state easily. The carbides moved very little leaving a very porous hone, and burrs ruled the roost. With proper selection today’s stainless can exhibit many of the benefits we enjoyed with 1095C carbon without the visible rust. Most people believe “Stainless” means “Rustless” however that is not the case with hunting blades. Slower to rust – in most cases. Harder to see rust – most definitely. But add enough carbon to heat-treat well and rust is a way of life. Replace often or carefully touch up edges maximizes their usefulness.
The two most used stainless alloys for hunting blades is a modification of 420, 440C. The 420 models are rather durable, grind nice and are very rust proof. But one of the drawbacks is the poor movement of carbides. While durability over the entire blade is good, the cutting edge suffers. It enters the cut rather sharp but exits rather dull.
The Swiss and German version of 440C (will name as AEB-L) when cryogenically heat treated has very mobile carbides. This makes steel that rusts easier but has carbides that migrate to the seam. This means an AEB-L blade cryogenically hardened to 55Rc and cutting edge properly honed, will have a cutting edge considerably sharper than 55Rc in standard 440C. Producing a blade that maintains its durability, but more importantly maintains its sharpness though the cut, producing an edge known as the 1095 of stainless.
What we are also able to do with AEB-L is hone extremely fine. Whereas an average hone is 300-500 for hunting blades we are able to be 500-800 easily. This means less dull space and more sharp space on each blade. Less destruction of blood platelets means less modification of those platelets. The less platelet modification the longer it takes for a cross-link of fibrin to make a clot.
For simplicity, the finer the hone the longer we can prolong clotting. If the brain/spinal cord or aortic arch is struck it probably makes no difference as death is usually quick. Miss your mark even by a little and the finer hone means sharper and that means more that cuts.
