Jasper Tools 200 Circle Jig

Plunge Router Cutting Jig for Speaker Holes

The Model 200 Jasper Tools Circle Jig was designed primarily for making speaker cut-outs and flush mounting speaker drivers. The Model 200 allows the speaker-builder to be able to make 256 different size circles in 1/16 inch increments. This will enable holes to be easily made for tweeters all the way up to subwoofers! It is the first true one-pass circle jig. Trial cuts are not necessary when using the Model 200. 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 flush against the wood for a very professional finish with the added benefit of reducing sound diffraction against the speaker's edge. (See photo further down.)

Jasper Tools Model 200 circle jig in use (router not included).

The Model 200 will cut circles from 2 1/4 inches to 18 3/16 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 200 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.

Jasper Tools Model 200 in use.

Instructions

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 Tools Circle Jig Model 200 is designed to make circular cuts from 2 1/4 inches to 18 3/16 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 back 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: The jig has inches listed along the horizontal scale on the bottom edge of the pivot hole pattern, and the fractions listed vertically along the left end. To find the 12 1/2 inch pivot hole, find the 12 inch column of holes from the horizontal scale and the 1/2 inch row of holes from the vertical scale. Follow these lines to the 12 1/2 inch pivot hole and insert your pivot pin there.

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.