The process of tuning a compound bow is considerably more complicated than tuning either a recurve or long bow since several steps must be taken such aligning the arrow rest for true center shot while also making certain that the arrow’s fletching has room to clear the rest as it passes through the rest, adjusting your nock point to the correct height for your particular bow and, making adjustments to the length of your cables and harness in order to synchronize the cams. Thus, if you have not already applied this process to your compound bow, then you definitely should consider doing so and, if you have, then you might want to consider “paper tuning” your bow just to make certain that it is still in tune before you venture into the woods next Fall.
So, order to correctly tune your compound bow, the first thing that you need to do is to make certain that your arrow rest is properly aligned to true center and, in order to accomplish this, you need to nock an arrow, place the shaft in the arrow rest, and then use the rest’s vertical adjustment to set the shaft at a height such that the center of the shaft sits level with the center of the plunger hole in your riser. Then, once the rest is positioned at the correct height, it then needs to be positioned at the correct distance from the riser such the shaft of the arrow is parallel to the face of the sight window. Thus, one method of accomplishing this is to use a small ruler to precisely measure the distance from the riser to the center of the shaft at both the front and back of the sight window. However, the method that I use is to position my eye so that I can look down on the arrow shaft from above and then I note the amount of distance between the arrow shaft at the front and back edges of the arrow shelf and then I use the rest’s horizontal adjustment to position the shaft so that it is parallel to the edge of the arrow shelf.
Next, you will need to make certain that the either the nock point or D-loop (which ever you use) is positioned at the correct height and, in order to accomplish this, you will need to use a device called a Bow Square. So, in order to use a Bow Square (which looks like a letter “T” with two clips on top) you will need to position the “arm” of the square in the arrow rest and then attach the two clips you will find on the top to the bow string. Then, you will need to move the bow square either up or down until the arm sits squarely in the arrow rest while it is attached to the bow string. Next, you will see several graduation marks on the edge of the square adjacent to the bow string and thus, you will need to position your nock point or D-loop in such a way that the top edge of the nock on your arrow is somewhere between a quarter of an inch and a half of an inch above level depending on your particular bow’s preferences. Thus, once the timing of the cams is complete, (provided that you shoot a double cam bow), you will then need to set the nock point, shoot the bow, note its performance, and then move the nock either up or down within this range until you find the optimum position.
Next, for those of you who shoot a double cam bow, you will need to make certain that both cams are synchronized such that they both turn over at exactly the same point. However, because this step requires the use of a bow press, actually adjusting the timing of the cams is best left to a qualified bow technician but, you (or an observer) can observe the cams as you draw the bow and note whether both cams are reaching their point of maximum rotation at the same time and, if not, then you can visit a local bow shop to have the timing corrected.
Last, in order to make certain that all of your adjustments are optimized, you will need to “paper tune” the bow and, order to accomplish this, you will need some sort of frame that can be positioned level with your bow when it is drawn. Then, you will need to attach a piece of paper to the frame and then stand back far enough from the paper such the belly of your bow when drawn is approximately three feet from the paper. Then, you will need to nock an arrow, draw your bow, and fire the arrow though the paper and into your archery butt. Then, you will need to examine the paper and note the shape of the hole it makes. So, if you have made all of the above mentioned adjustments correctly (and if your arrow has the correct spine), what you will see is a round hole the same diameter as your arrow shaft with three small, straight, tears radiating out from the center of the hole where the fletching has passed through. However, if you see an entrance hole where the point of the arrow has penetrated the paper and then a large tear extending in any direction (usually either up and/or to one side or the other) then further tuning is necessary. For instance, it the tear extends upward, try moving the nock point down slightly and, if the tear extends downward, try moving the nock point upward slightly and, if either of those steps do not correct the issue, then check the timing of the cams. However, it the tear extends to the left, the your arrow’s spine may be too weak and, if it extends to the right, then it may be too stiff. Thus, if the spine is too weak, then you can either reduce the bow’s draw weight or use a lighter broadhead (or target point) and, if the spine is too stiff, then you can increase the draw weight or use a heavier broadhead (or target point) or purchase new arrows with the correct spine for your bow.
Last, although this may sound like a complicated process to go through, it is actually relatively simple since any archer with a bow square and an eye for detail can properly set an arrow rest for correct center shot alignment and set either a nock point or a D-loop at the correct height. Then, it is simply a matter of shooting an arrow through a piece of paper and making slight adjustments until the arrow settles down as it leave the arrow rest and, once you have done so, you will likely find that you bow has suddenly become as accurate as your favorite deer rifle!