When setting up a bow it is important that the arrow fits correctly onto the string, it does not matter if you are using a recurve, compound or longbow having the correct nock fit is critical. Most nocks made are designed to snap onto the bow string but it is important the fit is not too tight or too loose.
The nock should fit onto the string in such a way that it snaps onto the string but still has enough movement to freely rotate an slide up and down the string. As you draw a bow back, the string will rotate, the nock fit should be such as to allow this rotation without placing excess side force on the arrow. This is particularly important on compound bows as the string rotation will affect the “Peep Sight” position when at full draw.
You can carry out a simple test to determine if your nock fit is correct.
Firstly, place an arrow on the string holding the bow in one hand so the arrow hangs down towards the ground (Fig 1).
Now with your other hand using your thumb and first finger, rotate the string. The arrow should not move (rotate) as the string is rotated but remain hanging down (Fig 2).
If the arrow moves with the rotation of the string and starts to swing then the nock fit is too tight.
Alternatively if the nock will not stay on the string then it is too loose.
Never wrap material (such as dental floss or cotton thread) around the nocking point to build up the serving. This can be used as a temporary measure only but should never be used as a permanent solution. This material can quickly wear giving you a poor fitting nock.
How do you correct this problem?
Many brands of nocks come with two hole sizes, .88 mm and .98 mm also called small or large hole, select the nock hole size that best suits your strings diameter.
Also, string serving material comes in different sizes, experiment and find which size material gives you the best nock fit.
If all this still does not work you can try laying additional strands of bow string materials onto the string and then serve the string over these additional strands.
For example, the bow string has 20 strands and is served with .22 thousand of an inch serving thread but has a loose nock fit. To correct, remove current serving, cut off a length of string material and lay 4 additional strands of bow string material on the string effectively now giving a 24 strand string, reapply the serving using the .22 thousand of an inch serving and check for correct nock fit.
The other alternative may be to obtain thicker serving such as .24 thousand of an inch, remove the old serving and reapply the thicker serving.