Jasper Audio 400 Circle Jig

Plunger Router Cutting Jig for Speaker Holes

The Model 400 Jasper Tools Circle Jig was designed primarily for making smaller speaker cut-outs, particularly for tweeters and midranges, plus it can also flush mounting speaker drivers. We like to think of it as a universal hole saw. It also makes a great guide. Manufactured from cast acrylic 3/8 inch thick, it can be left on the router as a sub base. It can also be used in place of forester bits in many applications. The Model 400 allows the speaker-builder to be able to make 105 different size circles in 1/16 inch increments. This will enable holes to be easily made for small tweeters and also for ports! It is the first true one-pass circle jig. Trial cuts are not necessary when using the Model 400. All you need to know is where you want the centre of the circle, the jig comes complete with a centre pin which you simply fit into the drilled hole and then pivot around it.

This jig also allows you to make partial cuts or rebates into the timber in the same easy fashion. Now you can mount the speaker driver or port flush against the wood for a very professional finish with the added benefit of reducing sound diffraction against the speaker's edge.

Jasper Tools Model 400 mounting.

The Model 400 will cut circles from 1 inch to 7 1/2 inches in diameter, in 1/16 inch increments. The jig has an easy to read scale that is calibrated for a 1/4 inch router bit. The Model 400 will generate circles that are smaller than the base of the router. This requires that some of the pivot holes be located under the router base. A matching centre locating pin is also available, the Model 350.

Instructions

Jasper Circle Jig Model 400 will make 105 different size circles in 1/16 inch increments from 1 inch to 7 1/2 inches in diameter. The scale is calibrated to read direct cutout diameter when a 1/4 inch router bit is used.

SAFETY:Read all the precautions that came with your router. Make sure your router is unplugged while changing the bit and leave router unplugged until you complete your set-up and you are ready to route your circle. Always use eye and hearing protection while routing.

GENERAL INFORMATION: The Jasper Circle Jig Model 400 is designed to make circular cuts from 1 inch to 7 1/2 inches in diameter. The pivot holes are precision drilled so that the jig holds the pin in the selected hole without falling out.

MOUNTING THE JIG TO THE ROUTER: Locate your router on the diagram on the front side of the package. Locate and mark the mounting holes for your router on the diagram. Align the jig over the diagram so that the mounting holes on the jig are aligned with the diagram. Locate the marked mounting holes for your router and mark the countersinks on your jig with a felt pen. Locate the jig on the router so that the holes that you marked align with the holes in the base of your router and mount the jig with the supplied screws.

HOW TO USE THE SCALE: While looking at the jig, find the first radial line labeled 1 through 7. The next radial line in the counter clockwise direction is labeled 1/16. As you continue in the counter clockwise direction around the jig, radial lines are labeled in 1/16th inch increments to 15/16. Fractional pivot holes for each inch are connected by a line around the jig. To locate, for example, the 4 5/16 inch pivot hole. You find the 4 inch pivot hole on the first radial line and follow the 4 inch line around to the 5/16 radial line. The pivot hole at the intersection of these lines is the 4 5/16 inch pivot hole.

CUTTING DISKS: The jig is calibrated to make HOLE cutouts using a 1/4 inch diameter router bit. To make disks, use a 1/4 inch router bit and add 1/2 inch to the scale.

USING OTHER BIT DIAMETERS: To make a cutout with a bit other than 1/4 inch diameter, select the pivot hole by using the following equation:
Pivot Hole Value = Cutout Diameter - Bit Diameter + 0.25

To make a disk with a bit diameter other than 1/4 inch, use the following equation:
Pivot Hole Value = Disk Diameter + Bit Diameter + 0.25

SETTING UP: The figure below shows a typical set-up for cutting circular holes, mortises, or disks. The work piece should be taped to the backup with double sided tape on both the inside and the outside of the cutout. Using a 1/8 inch diameter drill bit, drill a vertical hole through the work piece and into the backup. This hole should be located at the centre of the circle to be cut.

CONVERSIONS: To convert mm to inches: Inches = mm / 25.4. Use the following example to convert decimal fractional parts to fractional parts: If your cutout is 6.729 inches, you convert the fractional part (0.729) to 1/16ths of an inch by multiplying 0.729 x 16 which is equal to 11.664. Round this number up to 12. So your cutout would be 6 12/16 or 6 3/4 inches in diameter.

Set-up for circle routing.