While rotating the shaft you will feel a lump. That lump is the stiffest spot of the shaft and is called the spine.
Keep rotating the shaft and you may find a second spine or lump. Most times you find a second spine it is different in how it feels. The stiffest one is called the major spine.
Once you have found the spine(s) keep rotating and you'll find where the shaft wants to sit when you are pushing down on the shaft with the middle bearing. This is the softest section of the shaft and it is where I mark the position of the cock feather.
How hard do you push? Hard enough to know get the shaft to "lump" over when rotating the shaft.
Accuracy is all about consistency and once you have located your cock feathers in relationship to the spine you have a more accurate arrow.
This exercise will not help you kill more deer. It may help in getting better scores on targets and maybe turkeys at longer distances.
Static spine is measuring how much the shaft bends under load. The tool used to measure spines are not expensive to make and are widely available. In order to use a spine tester so you can match or sort arrows in spine category you have to locate the spine first. A spine tester can be made by building something that holds one end a bit above level and adding a weight to the free end. Measuring the deflection will indicate the stiffness of the arrow which is measuring the spine. The same can be done in the center. But you have to be consistently in the center.
Make sure you have the cock feather position up.
