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Forum topic by Angelicwood posted 10-18-2018 12:36 PM 392 views 1 time favorited 12 replies Add to Favorites Watch
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Angelicwood

5 posts in 29 days


10-18-2018 12:36 PM

I am looking for help before I start this new wood working project. I have acquired several small sheets of some really well laminated plywood. Ranging from 1/2 to 3/4 thickness. These sheets are around 2’ square. I am wanting to miter cut these with a bevel to make audio speaker horns. The tricky part here is that these sheets are not flat. They are pressed into the shape of a fattened “S”. With on end up and the other end down, with a difference of around a 2” rise and fall.
Any help would be greatly appreciated.


12 replies so far

View BlasterStumps's profile

BlasterStumps

942 posts in 612 days


#1 posted 10-18-2018 01:01 PM

you could make a jig to hold them while cutting them on a table saw but, without knowing more about the project, I might suggest marking the cut and simply cutting them with a good sharp handsaw. Clean up the newly cut edge with a block plane and you should have it. hope that helps

-- "I build for function first, looks second. Most times I never get around to looks." - Mike, western Colorado

View mahdee's profile

mahdee

4006 posts in 1940 days


#2 posted 10-18-2018 01:14 PM

Sandwich them between two straight boards, place the sandwich on table saw and cut it with the desired angle, flip it over and repeat.

-- earthartandfoods.com

View squazo's profile

squazo

109 posts in 1818 days


#3 posted 10-18-2018 03:30 PM

very difficult to imagine I think pictures are in order here.

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Angelicwood

5 posts in 29 days


#4 posted 10-18-2018 05:29 PM

Hi guys,
Thanks for your comments.
I am having some luck using my radial arm saw.
I am cutting 45 degree bevel, need to miter at a lesser degree to make horn flair outwards. This really makes some interesting wavy cuts. These horns are similar to what I am making.

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Angelicwood

5 posts in 29 days


#5 posted 10-18-2018 07:29 PM

Ok here is a pic of the plywood I am using.

View waho6o9's profile

waho6o9

8478 posts in 2750 days


#6 posted 10-18-2018 07:56 PM

The miter is on the long edge?

Maybe use a router with a 45 degree bit on it?

View Lazyman's profile

Lazyman

2559 posts in 1560 days


#7 posted 10-18-2018 08:02 PM

It is more like a mitered curve. The shape of the cut has to match the shape of the wave in the plywood compounded by the taper to get a horn. You won’t be able to cut that on a saw that cuts in a straight line (table, radial or miter saw). You will need to use a bandsaw or jig saw. The challenge, assuming I am visualizing this right, is that the blade has to stay at a right angle to the undulating surface in the direction of the cut, even while cutting a 45 degree miter or bevel perpendicular to the direction of the cut, while at the same time scrolling along a curve. It might be slightly easier if you get rid of the 45 beveled edge and use right angle butt joints.

But maybe I am over complicating this .

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View jbay's profile

jbay

2744 posts in 1072 days


#8 posted 10-18-2018 08:13 PM

How good are you with a file. Remove as much material as you can and dial in the 45 with your file.
It’s a pretty complex cut.

In my world (shop) I would use butt joints and veneer the exterior.

-- “Hanging onto resentment, is letting someone you despise live rent-free in your head.” (Ann Landers)......

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squazo

109 posts in 1818 days


#9 posted 10-18-2018 08:14 PM

so are you saying that you want a 45 degree angle on the long edge as though you had run a chamfering router bit down it (but in such a way that it is done perfectly)

Im thinking flatten it 45 45 it then bend it

View Lazyman's profile

Lazyman

2559 posts in 1560 days


#10 posted 10-19-2018 04:44 AM

It just occurred to me that there might be another way to make this cut that does not require you to cut a curved miter. I realized that you can approach this as you would to cut a piece of crown moulding for an outside corner, treating the wide part of the horn like the part of the molding that fits against the ceiling. Ultimately, it occurred to me that this is just a 4 sided splayed miter . I think you could do this by making a miter sled for the table saw (or jig for the radial arm saw) that holds the wood at the required miter angle as you slide it through the blade tilted at a 45° angle. Note that because the blade only tilts in one direction, your sled will have to work slightly differently when cutting the left versus the right side of each joint. If I am thinking about this correctly, one side will be cut narrow end first and the other wide end first.

Of course I could completely off base too. LOL.

Here is a good article that explains how to cut a splayed miter joint.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Angelicwood

5 posts in 29 days


#11 posted 10-19-2018 07:38 PM

Thanks for all of your thoughts on this project. I am still experimenting with cuts and will let you know how it progresses.
Lazyman’s observations seem to be spot on. Thinking of it like crown had occurred to me as well.

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Angelicwood

5 posts in 29 days


#12 posted 10-19-2018 10:19 PM

Thank you lazyman for including the article on splayed joints. Very useful with great setup charts! I had never heard of a splayed miter joint.

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