Scroll saw size is based on the distance from the blade to the back of the overarm. This is called the throat depth and may vary from 12″ to 24″ (305 mm to 610 mm). The throat depth limits the length of material that can be cut. 23.9.2 Selecting and Installing Scroll Saw Blades Blades for scroll saws are very narrow and so are capable of sawing a small radius. The number of TPI varies. A rule of thumb is to select blades that will have three or more teeth in contact with the wood at all times. This way, the edge next to the kerf will not splinter as much. • Variable. A variable speed scroll saw adjusts while the machine is running. • Pulleys. A belt is tracked over opposing step pulleys. Make sure that the switch is off and power is disconnected while you move the belt. 23.9.4 Scroll Saw Operation There are two types of cuts made with the scroll saw. One is around or through the work- piece, typically called an outside cut. The other is an interior cut for pocket cutouts. An example of a pocket cutout would be a hole cut out of the center of an object. 23.9.3 Scroll Saw Setup Preparing to use the scroll saw requires just a few simple steps. For saws having a guidepost, raise or lower the post so material can pass under the hold-down. The scroll saw may have one of three speed adjustments. • Electronic. A speed knob adjusts the speed, which is displayed in a digital readout. Beveling Beveling on the scroll saw is done much like the band saw operation. Tilt the table, and then adjust the hold-down to the tilt angle, Figure 23-55. Keep the workpiece on the same side of the blade until the cut is complete. 398 Section 4 Machining Processes Copyright Goodheart-Willcox Co., Inc. Changing a Scroll Saw Blade The procedure to change a blade is as follows: 1. With the machine off, disconnect power and lock out the saw. 2. Remove the table insert (if equipped) and loos- en the blade tension. 3. Move the lower blade clamp to the top of its stroke by turning the motor shaft knob. 4. Loosen the thumb screws or set screws on upper and lower blade clamps. 5. Remove the old blade. 6. Slip the replacement blade into the lower blade clamp. Point the teeth downward and toward the front of the machine. 7. Tighten the lower blade clamp to secure the blade. 8. Pull the upper blade clamp down, insert the blade, and tighten the screw. 9. Tension the blade and install the table insert (if equipped). Procedure Making Outside Cuts The procedure for outside cuts is very similar to the procedure used on the band saw. For outside cuts, proceed as follows: 1. Plan your sequence for making relief cuts. Even though the scroll saw has a narrow blade, relief cuts may help when cutting small radius curves. 2. On tension sleeve scroll saws, lower the hold- down until it rests on the material. Press lightly on the blade guard, and then tighten the guidepost. The hold-down on some rear-tension saws adjusts automatically to the workpiece thickness. 3. Aim the air nozzle at the point of operation. 4. Adjust the blade speed if necessary. Saw thick and hard materials at slow speeds. Faster speeds and fine tooth blades are appropriate for thinner materials. 5. Fine tooth blades leave smooth cut edges. 6. Start the machine and proceed with your cutting sequence. Relief cuts prevent having to back the blade out of a long saw kerf. Procedure