Best way to enlarge the stock speaker hole?

[JWPrendergast]

Ive been salivating over the Jl M7.7" speakers, so I purchased a set today (should be here by the end of the week). I need to open the speaker hole to 6.25"; whats the best way to do this? Big ass hole saw? Dremmel? Flapper wheel?

 

[Speedling]

Whats stock size? I forget.
jig saw would be fine except for the fact its made from fiberglass. Flapper wheel is good idea actually.

 

[David Analog]

There are a number of methods. Also consider that some will create a larger mess than others dispersing fiberglass dust all over. So having a second set of hands with a vacuum against the work surface as you are cutting is important. Wears masks and goggles.
Flap wheel or disc? Nope.
If you can find the right hole saw size, you can use a smaller hole saw inside that fits the existing hole as a guide. Or, you can install a wood plug to fill the existing hole and drill a centered pilot hole.
A plunge router with an MDF template that is double face taped in place. The particular bit type and rotation will be important. The wheel guide will need to be at the router base end rather than at the tip of the bit.
A die grinder or dremel with a rasp bit.
A die grinder with a spindle sanding drum although that is a lot of work for opening up what will probably be a .625" radius. Perhaps more of a finishing tool.
A jig saw which may not allow access all the way around.
A reciprocating air saw which is compact and allows complete access.
The surface should be well covered with painters tape.
Any hole saw should begin in reverse until it deeply scars through the surface gelcoat.

 

[KXCam22]

I way I use is to cut a piece of plywood and put it behind the hole and attach it using screws in the speaker attachment holes. Then you can measure and drill a center hole and use a large hole saw. Other than than the easiest is to mask the area, mark the larger hole and use a saber saw to cut the new hole. It will be a bit rough but is hidden by the speaker and trim. Hope this helps. Cam.

 

[Jeff0319]

I had to cut front speaker holes in my old LS2000. I put blue painters tape over the whole area and then traced where I needed to cut. I found that a dremel tool worked the best. Take your time, but it was a clean cut.

 

[JWPrendergast]

Jeff0319, what dremel attachment did you use?

 

[JWPrendergast]

Here is a sketch of what im considering doing. I cant seem to find a 6 1/4" hole saw that would be good for fiberglass AND not cost a fortune. What im thinking about using is a 6 3/8" carbide grit hole saw (pictured in blue on sketch). This would make the hole slightly bigger than needed, but still leaves room for the bolt holes (small dark blue circle on sketch). These hole saws are much more affordable and better for cutting out fiberglass vs. hole saws with only a few large teeth. Does anyone have any thoughts about this?

 

[Jeff0319]

I don't know the exact name, but it looked like a drill bit and was made for cutting wood. I went through two or three bits though.

 

[Addicted]

I used a multi purpose cutting bit for my Dremel, and used the long flexible attachment. I also held my shop vac close to the cut, and it picked up 90% of the mess. It was quick and easy. That bit cut through with relative ease, but not so much that it was difficult to control. I went through a bit for every 2 holes.

 

[txav8r]

David gives the options. I would follow one of them...two of them actually. Either the dremel for the less accurate but certainly doable method, of just widening the existing hole to a line you draw on blue tape. Use the sanding drum wheel, not a cutting bit. This will be slow but controllable. The tape will create havoc with the sanding drum but it needs to be there. If you use a cutting bit it will fray the fiberglass. If you used a jigsaw so close to the edge like that, you will get more fraying as well...and as David says, you won't be able to make all radius turns due to clearance issues with the body of the jigsaw.

The best option is to lay out the inner and outer diameter of the speaker ring like you have in your drawing, on a piece of MDF, and make a template. Just double side tape it over the existing hole and use a template following bit in a trim router to trim away the excess fiberglass. These bits are also called flush trim bits. They have a bearing installed on the end or bottom of the bit that follows the edge of the template precisely, and lets the bit cut a controlled line matched to the templates inner edge. I would also try to match a couple of holes that I would use for mounting screws so that I could run a couple of screws through to secure the template to the surface for an extra measure of both safety and security to prevent a wandering cut.

Here is the JL audio YouTube video of the install on the Yamaha 210, using existing holes and installing the 770's. They did it how I described in the above paragraph...

 

[txav8r]

Best of all...it is an excuse to purchase a trim router!!! That is a tool that will get use from now on! You will love doing it this way...perfect holes, safe, easy, and professional.

 

[MNdrifter]

A man after my own heart. I always tell my wife that I pick my woodworking projects based on what tool I want to buy next

Best of all...it is an excuse to purchase a trim router!!! That is a tool that will get use from now on! You will love doing it this way...perfect holes, safe, easy, and professional.

 

[Julian]

I used my Dewalt cordless cut out tool. Was really easy! I was cutting 6.5 holes to accommodate 6x9 polks. The 6x9s came with 2 bezels and I only needed one, so I used the 2nd bezel as a cutting guide for the hole as the inside edge of the bezel is exactly the same as the hole size needed for the speaker. I took the bezel, clamped it over the existing hole with some c-clamps and then took the cut out tool to the hole. I had to move the clamps when I got to them, but that was easy.....just applied 2 more clamps first then took the 2 in the way ones off....and finished the cut. And yes, if you can have someone manning the shop vac while you are doing this....that helps!

http://www.dewalt.com/tools/cordless-specialty-cordless-cut-out-tools-dc550b.aspx

 

[JWPrendergast]

I went ahead and ordered a hole saw after all. I figured with all the money I have (and will) spend on this boat, $50 for a hole saw bit that ill use to make 4 holes larger, and add 2 extra holes mid cabin, will be worth it. Looks like those JL M7.7s will fit PERFECTLY! Im glad I went with the ones I really wanted. Ill have 1 set installed by next weekend, but wont post an update until ive ordered and install all 3 sets.

 

[David Analog]

A hole saw is safe with less mess and makes a precise hole. Just begin in reverse and keep the speed moderate with minor push. But keep both hands firmly on the drill. If that saw catches and grabs it can hurt you.
You can rear load and screw the wood insert for the pilot hole to the exterior of the old hole and to interior of the new hole. Obviously the block will freely spin once you cut through the fiberglass. Just control any reaction to pull back. Follow through.
Or....you can create a 5-inch round diameter (assuming that's the size of the old hole) and deep (multi-layer) wood circle as a guide for the old hole. Simply screw it to the hole saw through the holes or slots provided in the back plate.