Hole cutting made easy

[Don Mascali]

I just finished doing the circle cutouts on the front baffle boards of my new speaker project. I thought I would do a “how to” for those who may be new to this hobby and save them some time climbing the learning curve.

First, this may sound like an “Info-mercial” for the Jasper Circle Guide. It is! I have built quite a few speakers using a jig saw to cut the holes. Man did I waste time and energy. This little marvel will help you cut perfect holes, 2 ¼” to 18 3/16” with ease. That covers every driver JBL makes and if they don’t make it you don’t need it, right?

I had to cut a 12”, a 15” and two 4 ½” holes in each of four baffles. I hate to think about how long and how ragged looking a job that would have been with out the guide. I purchased the guide from Parts Express for under $40.00 and I feel like it paid for itself in reduced frustration alone.

The guide attaches to a standard “Plunge Router”. Mine is a Porter Cable #1001-T2 and I used a ¼” round carbide plunge bit, Porter Cable #2880201. Any brand will do of course but you should use a carbide bit. MDF and particle board will make short work of a high speed steel bit.

You start off by laying out the center of the cut out and drilling a 9/64” hole. The center pivot pin of the guide is 1/8” and I found a little larger hole worked better as the pivot pin stuck in the hole with an 1/8” hole. I used the exact measurement from the JBL .pdf documents. The marks are very well calibrated for the ¼” bit and are laid out by 1/16”. You insert the pin in the marked hole on the guide plate for the desired size and then insert the router and guide with the pivot pin in the hole drilled as center. When using ¾” material I set the plunge guide for ½” and did the front by turning the router clock wise 360 degrees around the pivot pin. Then turn the piece over and repeat. This leaves a nice edge on both sides, where trying to do the entire cut was problematic. It helps to keep another board under the cut as the puck wants to move or fall out when you get to the end of the cut. Having the support underneath gives you more control.

A word here about hearing protection, please use some! Routers scream at a high frequency and nothing will make your tweeters useless quicker if you aren’t protected.

I hope this proves useful and if any of the more experienced builders have something to add, please do so.

Good luck,

Don M

[Titanium Dome]

Did you take any pictures?

[duaneage]

I've used the Jasper unit for years. With the right bits you can really get creative on speaker baffle boards.

[boputnam]

Search for "Jasper" - there's tons of great reports.

http://audioheritage.csdco.com/vbull...ghlight=jasper

[Ian Mackenzie]

Don,

Nice post.

Any pics ....oh found some. Here a 4345 baffle in progress.

The dust when routing MDF is a bit of a problem. Always use safety goggles with a router (or any power tools) and a diposable face mask to avoid the dust going where it shouldn't.

I also found double sided tape useful to hold the cutout in posting when you cut right through.

Ian

[Edwards]

I have always made a template by taking a piece of plywood ripping it in half, drawing the circle, carefully cutting it on my bandsaw, Sanding any high spots, and then quickly securing to a few 3/4 inch cross pieces. See first photo.

Once I have the pattern, I use a patern cutting bit, to cut(route) the identical pattern in the finished piece. (see photo #2)

I even secured side pieces for ensuring perfect line up. You just clamp and route. This works everytime, and is very easy to line up and create multiples, with no additional drawing, or measuring. I have done some fairly large signs, and other pattern routing in this identical manner.

See attached.

[Baron030]

I thought I would share with you some ideas for cutting those smaller port sized holes.

I have found that a plunge router equipped with a 1/2" pattern router bit works really well for this application, provided that you have a pattern to work from. Pattern router bits have a ball bearing guide wheel that allows the cutter to follow a pattern.

For my latest project, I decided to use Schedule 40 PVC plumbing pipe for all of the bass reflex ports. PVC pipe works well for ports, and it's really cheap. But, unfortunately all of the standard pipe sizes come with some very non-standard outside diameters. So, a drill equipped with a hole-saw bit is not best tool for the cutting PVC pipe port holes.

So, I needed to come up with a way to cut very precise holes for the PVC pipe.Well, the perfect "pattern" for PVC pipe turns out to be a PVC pipe coupling.
For this trick to work, all that is needed is a way to temporarily attach the PVC pipe coupling to the inside of enclosure, during the hole cutting operation.

Using, some J-B Weld epoxy and a small block of wood, I fabricated the custom "pattern" tools seen below. Simply rough cut a hole in a block of wood and glue a PVC pipe coupling into the opening. A little trick to making this custom "pattern" tools is to use a sheet of aluminum foil as a release agent. Otherwise, you will end up gluing a small block of wood to your work bench.

Also, required for my latest project, I needed to come up with a way to cut very precise holes for a pair of 2405 drivers. Well, it turns out that the perfect "pattern" tool for this task was actually made by JBL. It's an old 075 mounting plate. So, needless to say, the drivers fit perfectly.

Baron030