Driver Cutout Tips

[ChrisR1983]

Hi

Can anyone share the best ways to do driver cutout if you have limited tools?

I do have a router; what type of bit do I need?

Does anyone just use a hole saw and then sand/file away?

Thanks

Chris

[richie00boy]

Buy a Trend N-Compass and a template following bit with bottom cut (plunge). Then you cut the hole so it's almost through, then on the final run plunge down through and the bearing will guide you round the top of the newly created hole.

[stephenmarklay]

Is a "plunge" router required? I have a new circle jig and wondered if my fixed base router can be used or should I get a plunge type?

[richie00boy]

Without plunge you will have a job getting the pivot pin in the hole.

[Francec]

I've built a circle cutting jig for my plunge router based on the attached. I've added aluminium guides down each side of the base plate and it is very secure.
What I need is a pivot pin; one that canned be screwed into place into several points along the length of it.
Does anyone have any suggestions, please?

Frank

[dangus]

I use a non-plunge router, but it's a vintage B&D Pro (same as DeWalt but not yellow) with the rack and pinion depth adjust which can be lowered easily. A quarter-inch straight carbide bit does the job. I've tried a spiral upcut bit, which ejects material from the groove, but doesn't make as clean a cut on some materials.

For big driver holes, I use a DIY circle guide based on something I saw in Speaker Builder. Scrap plywood with a 1/4" slot and a wider recess. In the slot goes a T-nut with the barbs cut off, a long bolt and a washer. The bolt is the pivot. Easy to make if you have a router and a 1/4" straight bit.

For small drivers, I bought a Black & Decker guide that has an offset pivot that allows putting the pivot under the router footprint. Not my first choice for big holes.

[lloop9]

Hey guys, good recommendations. But what is the driver frame is not round, such as the MCM 55-1853 woofer in Zaph's ZBM4? Other than making a template & using a template guide (which bring us to the issue of making a precise template itself)...

[dangus]

I've never gone the template route. I did buy some hardboard with the intention of making one, but I found the hardboard frayed too much. If I did have to make one, I'd find a material that can be filed cleanly. If possible, create the template using CAD and print on adhesive label stock. Otherwise, if the surface doesn't lend itself to drawing on, cover with a blank sheet of self-adhesive paper. Lay out a a couple of lines at right angles to align the mounting holes with, and place the driver face down over the lines. Mark the holes. Use a fine drafting pen or pencil with something around it to match the diameter of the router bit bearing to trace the driver flange. Cut the hole undersize, and file or sand carefully up to the line.

[mightydub]

It is pretty easy to make a guide for an arbitrary shape.

1) mount the driver in a 1/4" piece of mdf/hdf with enough space around the driver to accommodate the diameter of your router base. You may have to shim the driver up a bit so there is enough height to guide the router. Make sure to draw lines through opposite screw holes that will be long enough to go outside the cut out portion, these will be the guide for later alignment.

2) hold the router tight against the driver to use it as a guide, route all the way around. You'll end up with a big hole.

3) On a new piece of mdf/hdf, draw a set of lines at 90 degrees and line them up with the lines on the pattern from step 2. Use 1/2" material so that the final template is thick enough for the router bushing used for the next step. Put the router inside the big hole created in step 2, use it as a guide for the router base to route a cutout in the new piece. This new hole will be the template for creating the cutout for the driver.

4) Assuming you used a 1/4" router bit, use a 3/4" outside diameter router bushing to follow the template from step 3 to route the driver cutout. Again, draw lines at 90 degrees through the center of the hole for the driver and use them to align the template.

I used this technique to do flush mounting of HiVi TN25s (square with rounded corners), it worked perfectly. Maybe it is obvious, but the minimum radius of curves/corners is the same as the router bit. Sketch it out on paper if you're not convinced it works. You can also use a smaller router bit and adjust the size of the bushing appropriately.

[ChicagoJTW]

The frame shape doesn't matter that much; it's the shape of what drops through the hole--which is likely round. Try resting the driver over a pan or other container of appropriate size. I doubt the rectangular frame comes into play.

As far as the hole goes, you can use a circle jig, a sabre saw with a fine-tooth bit or, for small openings, a Forstner bit. I would not recommend a hole saw for most woods. If your material is plywood, be sure to tape all around the cutting area to prevent tear-out. If you are veneering, it's less of an issue, but always good practice when cutting plywood across the grain.