21 Jul 2005
Many times bowhunters are frustrated by a loss of accuracy and a change in impact when shooting broadheads instead of target tips. To fix this problem and get the best accuracy out of hunting arrows it is important to do what is commonly called "tuning your broadheads."
Every arrow as it leaves the bow is undergoing a series of flexes that do not dampen out until the arrow is many feet clear of the bow. Slow motion photography shows these flexes to be up to several times the thickness of the arrow itself. Often multiple flexes are occuring and the arrow appears like a snake as it leaves the bow.
The arrow point follows these flexes. When that point is a broadhead these flexes are pushing the side of the blades against the resistance of the air causing a defection (or planing) of the arrow. Tuning broadheads is positioning the broadhead on the arrow shaft to minimize the effects of these deflections.
The first step in broadhead tuning is having a well tuned bow with properly matched arrows. Arrows from a tuned setup wobble and flex less, and will often group broadheads very well without any extra work. However, even a tuned setup can benefit from the next two steps.
The second step is to orient each broadhead on the shaft so that its blades are in the same position in relation to the cock vane as every other arrow. By orienting all broadhead blades identicaly the deflection they cause will be the same for each arrow. Arrows that undergo the same deflections will group tighter then ones that deflect differently.
For three bladed broadheads the easiest and best way is to align the blades with the vanes. With four bladed broadheads pick an orientation and make them all the same. For two bladed broadheads or broadheads with two main blades and small bleeder blades it is best to orient the main blades so that their cutting edges align with the dominant nonforward movement of the arrow.. To determine the dominant movement shoot the arrow through paper (see paper tuning), if for example you have a slight up and down tear, align the blades verticaly, If your tear is left-right set them horozontaly.
If your arrows are aluminum with hot melt glue holding the insert, all you have to do to change broadhead orientation is warm the insert and shaft until the glue softens, turn the broadhead and insert until it is positioned where you want it, and let the glue resolidify. On carbon arrows with hot melted inserts do not heat the shaft, instead thread a field point into the insert and heat the tip, letting the heat work its way back the insert until the glue softens and and it can be turned. After it cools exchange the field point for the broadhead and recheck alignment.
Carbon arrow inserts are often glued with epoxies or other permanent glues. The best way to orient broadheads is to have them in the inserts when they are glued. If thats not possible try your broadheads in each arrow, often several will orient in your desired position. There are two ways of aligning the rest. My preferred method is to refletch the arrow, setting the jig to align the fletching to the broadhead. The other method is to use small plastic or rubber o-rings between the broadhead and the shaft. These rings compress and hold the broadhead even when it is not screwed firmly against the shaft, however they add weight and make it harder to complete the next step in broadhead tuning.
The next, and final step, is to center the broadhead on the arrow. Off center broadheads are ones whose blades are not parralell to the shaft of the arrow. Either spin the arrow on the point of the broadhead like a top or spin it in spin tester tool. If you can detect any wobble in the broadhead or shaft the broadhead will need centered.
If the insert is hotmelt glued soften the glue as when orienting the broadhead and with gentle finger pressure push the tip towards center. Let the glue harden, respin the arrow, and repeat if needed. If you are good this step can be completed at the same time you orient the broadhead.
With permantly glued inserts the best way to center broadheads is with the ASD tool (stands for arrow squaring device) from G5. With this tool the arrow shaft is turned against a blade which shaves any high spots from the insert and "squares" it to the shaft. A broadhead that does not spin true after being screwed firmly against a squared insert is itself at fault. This problem can mostly be avoided by purchasing quality broadheads to start with, 12.99 Walmart specials just won't make the cut!
Once your broadheads are tuned shoot them and check your groups. If you are still not satisfied try adding more helical or longer fletchings to your arrows. The little bit of velocity you sacrifice by doing so may be a good trade for an increase in accuracy.
Many archers are not happy until their field tips and broadheads impact the same point. This is because they do not want to change sight settings when practicing with different tips. If your arrows with tuned broadheads still do not impact with field tip arrows sometimes they can be brought together by microadjusting the arrow rest in the direction the field tip impacts. For example, if the field tip arrow strikes higher in the target then the broadhead tipped arrow, raise the rest a very small amount and try again. However this will not always work and can have negative affects if carried to extremes. Sometime it is best just to accept the changes from the broadheads and set your sights accordingly.