This is where it gets a little tricky-this is something that can only be specifically explained with expensive and obscure spring-tensioning tools and meters, so you'll just have to feel this one out. Slide the armature bar onto the arm. post sideways and snug the screw.
You don't want too much tension on the arm. spring, or your machine will hit weakly, however not enough and your spring won't pull your arm. bar back up hard enough to make a good connection and will make your machine stall out and sputter.
Now you have to do the contact spring-it should have just enough tension on it to make it move down a millimeter or two when the arm. bar pulls it back up and it makes contact with the contact screw. If this spring has too much tension it will keep contact with electricity too long and re-connect too soon, which will shorten your throw-contrary to popular belief the distance the arm. bar nipple moves when you press it with your finger is not necessarily your throw, your throw is also affected by spring tension, if your arm bar tension is high and your contact spring tension is low, your contact spring may be bent too much from being pushed up too high by the arm spring, making for a very strange throw. I've also heard of a machine that was cutting a figure 8 pattern at the arm nipple instead of just reciprocating-the cause was a broken fork on the armature spring-the springs will do some funny things, so it's best to understand how they function.
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