Speaker building-DIY Panel Cutting Jig

To make a speaker cabinet you are basically building boxes. The panel cuts must be precise and square. There are several ways to do this, but a Panel Cutting Jig is the easiest. I'm going to show you how to build one simply and cheaply.

For years I cut panels like this using as a guide an aluminum straight edge clamped to the wood. The problem is you need someone to help hold the ply to keep it from dropping and breaking as you finish the cut. Also, as you cut and push against the straight edge, the straight edge can bow slightly in the middle . To prevent that you can put a row of small brads or finishing nails along the opposite side of the straight edge. This leaves a row of tiny holes, and that side needs to be on the inside of the speaker cabinet. You should always make your cuts with the "good side" down so as to minimize splintering of the edge.



You have to be aware of the distance from your straight edge to the cut, as well as the width of the blade, so that you can make your cut at the right place.





So, what is really needed is a jig that can (a) hold the panel to be cut so that no assistance is required, and (2) guide the saw so that a perfect square cut can be made, a perfect 90 degrees.

Here you can see the completed panel cutting jig. It is made from 7/16" OSB aka "wafer board". This material is cheap, only $8 per 4'x8' sheet.



This photo is from the upper side of the jig. This jig is 4' wide x 5' tall. As you can see, there is a two layer thick horizontal support (the blue edge from side to side under the saw), which stack up to be 7/8" thick. This allows 3/4" ply to be slipped in under the cutting tracks without binding. Those pieces are 4' long x 6" wide.

The horizontal support along the upper edge (near end in this photo) are two pieces of OSB 4' long x 5" wide. Since the whole jig is 5' tall (60" - 6" - 5" = 49"), this allows a 4' wide panel to be placed in the jig with an inch to spare.



Here is some end detail from the "top" end of the jig. There is one additional strip added to the bottom to reinforce the 4' x 5' panel due to the fact that the saw will cut into the jig slightly.

The tracks are also made from two layers of OSB, and the metal straight edges attached with countersunk flathead screws. At first only one straight edge was attached. The track was secured at both ends with only one screw on each end. It was lined up by measuring from the outside edge of the jig. Then a test cut was made, and the cut wood checked for square. I found it to be off slightly, so I removed the screw on one end, adjusted position, resecured the adjusted end, and made another test cut. That piece checked out perfectly square. I then secured that side of the track with several additional screws on each end.

THEN the other straight edge was added by placing the saw at various places along the track, pushing the second straight edge up against the other side of the saw, and drilling and screwing it down.



If I ever get a new saw, I can simply move one straight edge to fit the new saw.



Here you can see that the saw is adjusted for depth of cut to just cut into the backing panel about 1/8".



This view from the "bottom" end.



A look down the first straight edge for straightness. Looks good to me!



Panel Cutting Jig finished.



Back side. There is a strip down the center to reinforce the cutting area. This piece is glued and screwed on. So that it rests evenly on the ground, there are also strips along both outside edges.



DOG! PUT THAT LEG DOWN... your tree is over there!!!

Anyway, now it is ready to cut panels up to 48" long.

One more hint... This saw uses 7 1/4" blades. For building speakers, making smooth precise cuts, I prefer a 40 tooth carbide tipped blade.

Nice jig, Paul, looks like it do a real fine job!

FWIW, another trick of the trade is to use a 4'x8' sheet of insulation as a sacrificial table. Anything over 3/4" should work fine. Just lay your sheet goods on it, set your saw blade depth shallow enough to cut the sheet goods, but not through the insulation and you'll have all the support you need.

I have a couple pieces of 3/4" foam I use for that purpose. I rough cut the sheet goods with the handsaw and finish up the small, much more handleable pieces on the table saw.

A second trick is to have the guys at HD use their saw for rough cuts too. I use them a lot to make the 4x8 panels fit into the Explorer. As long as you know where some of you major cuts are going, it works swell. 5 cuts for free too, and $0.50 each after that can't be beat.

Neat, Paul, if you make a lot of speaker boxes that ought to be just the thing.

I made a similar gadget for crate building, not as fancy as yours. With a plywood blade and accurate clamping you could do pretty fine work. I'd cut three panels at a time by screwing the sheets together in waste areas.

I eventually made huge outboard wings for my table saw to handle a guided 4' rip with enough table behind and beside the blade to support a full sheet with only one man at the saw. Made a great work table when not used for sawing.

I work at home now and barely have room for the saw. Back to rough-cutting oversize on sawhorses outdoors and final trimming on the tablesaw.

-Ed

Very Nice, Paul!

Geez Paul, I'll bet that saw is older than most of the gear we talk about here

Go, make fun of my saw... but it has cranked out a lot of nice speakers over the years!

:scratch2: It's about 30 yrs old. I replaced the power cord a few years ago.

I think I have the matching panel sander.:thmbsp:

Nice jig Paul, Building bottoms for all those horns?

Thanks, Jay!

I have four speaker projects to do in the next few months. This should speed things along.

I'll do a show and tell on those, too.

I have an extended table on my Ryobi. I can do 66 inches off the blade. I use a ripping guid on the circular saw that goes to 23.5, that seems to work pretty good too.

Looks great, Paul. After making one cube subwoofer enclosure and a pair of Pi 2 tower cabinets, I've spent much of my daydreaming time pondering square cuts. It's much like the hackneyed riddle, 'The sound of one hand clapping" and quickly induces a meditative, ineffectual stupor.

I assembled the four walls of the Pi towers first, then glued on the top and bottom. Glue went around the perimeter of the bottom, tower assembly on top of that, then the top on the whole thing. As clamps, I used three come-alongs (Harbor Freight) and tightened those bad boys down until they'd sing when strummed. It made a good seal, but the bottoms are nowhere near square and wobble like cheap diner furniture.

Very nice. Just another project to do at work instead of working.