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DIY Circle Jig
For past speaker projects I had thrown together quick simple circle jig consisting of a piece of 1/2" piece of MDF bolted to the bottom of a router with a hole drilled for a small bolt to use as a center pin. Similar idea to a Jasper Jig, but without the pre-drilled holes. It worked fine but setup was tedious since the only method of adjustment was to drill a new hole for the bolt each time.I decided for my current Continuum and sub project that I would make a better jig, one that was easily adjustable to an infinite number of positions. I did some looking online at other DIY jigs and come up with one that I think will work pretty nicely. Mine fits the plunge base for my Bosch 1617 EVS but I think something similar could be made for almost any plunge router out there.
I think the pics are pretty self explanatory. The key to this jig is the offset pin and lock down bolt. It allows the pin to slide under the base of the router to cut holes as small as possible while leaving the locking bolt accessible from the top side of the router for easy adjustments. The pin is just the top of a 1/4" bolt cut off and epoxied in to a 1" wide strip of 1/2" baltic birch, the locking bolt is carriage bolt. This jig will cut holes from under 2" to over 22", the largest holes are made by reversing the offset pin piece so that the pin is further out that the locking bolt. The design could easily be modified to suit and size holes you want but I wanted to keep mine relatively compact while allowing me to cut holes and recesses for anything from small tweeters to 21" subwoofers.
The jig was built entirely from stuff I had kicking around in my garage, and can be built with basic tools that most speaker builders will already own. If you wanted to go to extremes I am sure a really nice version could be built from UHMW and some aluminum or steel. The only things I could see changing at this point are replacing the nut on the locking bolt with a large wing nut for tool free adjustment and maybe increasing the size of the cutout for the router bit for better sawdust removal.
I won't post any dimensions since some will depend on the size of the router base used. If anyone has any questions please feel free to ask.
Jason
I think the pics are pretty self explanatory. The key to this jig is the offset pin and lock down bolt. It allows the pin to slide under the base of the router to cut holes as small as possible while leaving the locking bolt accessible from the top side of the router for easy adjustments. The pin is just the top of a 1/4" bolt cut off and epoxied in to a 1" wide strip of 1/2" baltic birch, the locking bolt is carriage bolt. This jig will cut holes from under 2" to over 22", the largest holes are made by reversing the offset pin piece so that the pin is further out that the locking bolt. The design could easily be modified to suit and size holes you want but I wanted to keep mine relatively compact while allowing me to cut holes and recesses for anything from small tweeters to 21" subwoofers.
The jig was built entirely from stuff I had kicking around in my garage, and can be built with basic tools that most speaker builders will already own. If you wanted to go to extremes I am sure a really nice version could be built from UHMW and some aluminum or steel. The only things I could see changing at this point are replacing the nut on the locking bolt with a large wing nut for tool free adjustment and maybe increasing the size of the cutout for the router bit for better sawdust removal.
I won't post any dimensions since some will depend on the size of the router base used. If anyone has any questions please feel free to ask.
Jason
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