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Mechanisms

There are five types of scroll saw mechanisms:

1. Rigid Arm

2. Parallel Arm

3. Double Parallel Link Arm

4. “C” Arm

5. Oscillating Loop

Each has its own advantages and, in some cases, disadvantages.

Rigid Arm Saw

1. RIGID ARM

An example of the rigid arm saw would be the 1935 Delta jig saw. This saw had a heavy cast iron rigid arm that held the top and bottom of the blade at the ends of the arms. The motor pulled the blade down and a spring brought the blade up. This motion gave a perfect up-and-down blade motion. The blade tension always changed as the blade tightened on the down stroke, but loosened on the up stroke. This gave a very rough saw kerf. Unfortunately, more time was spent sanding the edges of the cut than cutting out the project. This mechanism was very popular from 1935 to 1975. Most saws took the large pin-type saw blades, so they could not do complicated fret work projects. This saw was very expensive in its day—in the sixties it sold for around $1700.

Parallel Arm

2. PARALLEL ARM

The parallel arm mechanism has two arms that pivot about two points (bearings). The two arms move up and down parallel to each other. This mechanism is the very same as it was in the early 1880s in pedal-powered scroll saws. The parallel arm mechanism gives an almost perfectly straight up-and-down blade motion. This near-perfect perpendicular motion allows you to make very sharp corners and precision cuts because the wood does not have a tendency to “pick up” on tight turns. If the blade breaks, the top arm stops immediately and swings up out of the way. This is an important safety feature.

3. DOUBLE PARALLEL LINK ARM

The double parallel link arm scroll saw mechanism incorporated two horizontal rods that moved back and forth horizontally. This back-and-forth motion of the rods is converted to an up-and-down motion at the ends of the rods. It is the up-and-down motion that creates the “arched” blade motion. This system gives a smooth blade motion with little vibration.

Double Parallel Link

The only drawback I see is if the blade breaks, the top half of the broken blade still moves up and down until the motor is turned off. This could be dangerous.

“C” Frame

4. “C” ARM

The “C” arm scroll saw mechanism uses an arm in the shape of a “C” with the blade attached to the ends of the arm. The “C” arm pivots about a single pivot point. Using this design, the blade moves in an arc—not straight up and down. This gives an aggressive cut but cannot make sharp turns without burning the edge of the wood or picking up the wood as you turn. For your information and as a safety point, if the blade breaks, the top half of the broken blade will keep moving until the motor is turned off. This could be a dangerous situation. While this model was popular years ago, I believe it is no longer made.

5. OSCILLATING LOOP

The oscillating loop mechanism uses a flexible, toothed belt that moves back and forth through a series of pulleys. This motion gives a perfect up-and-down blade motion without any vibration. It is smooth and quiet. The top speed is only 1350 strokes per minute; but because of the long 1 ½" stroke, it is one of the fastest-cutting scroll saws.

Note: The machine will stop immediately if the blade breaks.