Part 2 of 2
You have to continue counting until you achieve the active target coils in the completed compression spring. Then let it wind a couple of more coils. Keep counting and unfasten the lead screw. The wire lays on itself and starts forming closed coils.
If you have additional wire left, cut it. Afterwards, you have to put the compression spring in the oven to reduce any stress. In this trial process, you have to leave it inside for about thirty minutes. Remember that this process of relieving stress will make the music wire springs contract a little. In the case of stainless steel springs, it expands a little.
After completing the process, allow the compression spring to cool down at room temperature, i.e. by air-cooling. You can measure the spring to find out how near you are to the target. You should check the diameter initially. If the diameter is not correct, you need not bother to do any more measurements. You will require a different arbour which changes all the remaining dimensions of the compression spring.
However, if the diameter is perfect, count the active coils of the compression spring. If would be nice if you ended up quite close to your target. It is fair to be one-fourth of it off on either way for a smaller figure of springs. If it has more than 25% variation, you have to calculate how much additional or lesser you require and try achieving the target coil count next time.
You may also coil compression spring on your lathe without using the lead screw. But here the problem is that you may not make the same springs. Let us learn how to do it without a lead screw.