One of the things we get the most questions on is the use of the aluminum bar for the bending machines. What is the purpose of this and why do I need to use it is offen the question we get.
The answer is that you don't absolutely need it, but it sure makes things more accurate, especially when the length of the sides are quite limited in length. One thing you want to do is to make sure the center of the waist of each side is pertectly aligned with the form insert so the side length works out correctly with the head block and the butt joint of the instrument.
You will notice that on our side template for each of our instrument plans the center of the waist is clearly marked with a vertical centerline. This line should be adjusted to center of the waist slots on the form insert and also centered on the long vertical slot in the bending machine. After the side wood is all prepared and ready for bending. place a piece of masking tape on the edge of the side at this centerline and extend it over the top and bottom of the side a bit. With a permanent heavy marker, mark this centerline on the edge of the side wood so it can be clearly seen through the bender vertical slot.
Prepare the side to be bent by inserting the wood and silicone blanket between the 2 stainless steel slats. Be sure to align the instrument top, which would be the straight side of the side wood with the edge of the sandwich. Insert the sandwich into the bending machine over the top of the selected instrument form insert. Align the sandwich so the waist marking is visable through the bender vertical slot. Crank down the press screw and place some pressure on the waist.
Now insert the aluminum bar into the bending machine. It gets inserted through the long vertical slot in the bender, below the aluminum slats and sits in the waist slots of the form insert. Continue to crank on the press screw a bit if needed. Hook up the springs at the top of the bender on each side to the aluminum bar. The sandwich will be held tightly in place between the waist retainer of the bender and the aluminum bar. Make any final adjustment to see the waist marker on the side wood through the vertical slot and finish the bending operation. Also make sure the sandwich is perfectly straight in the bender.
When do you turn on the heater? I usually get everything aligned and have some pressure on the waist, even to the point of having the aluminum bar slightly down into the form insert waist slots, Thats when I place some spring clamps of each end of the sandwich to hold it together better and plug in the bender and let it heat up for a few minutes. When the side is starting to steam I run the upper and lower bout retainers around the form and then slowly crank down the waist retainer until the aluminum bar full sets in the form slots. Never force anything as you may not have the alignment correct.
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