# Best way to cut openings in 3/4" plywood



## MrRon (Jul 9, 2009)

I am doing a project that requires me to cut 8 openings in 3/4" plywood. The opening sizes are 16"x30" and 14-1/2"x16", 4 openings of each size. The openings will be covered by cabinet doors. I have 3 ways of accomplishing this. I can use a scroll saw; plunge cut on a table saw and finish the corner cuts by hand; Use a router with a template.
I'm inclined toward the router method, but I don't have a bit long enough, but I can go buy one. If I go with the router, I suspect I will have to make several passes at increasing depths. What do you think is the best way? I'm a bit leary about using a saw as I can easily get off line and ruin the cut. As the sketch shows, the openings are spaced far apart, too far to use solid lumber and I need the grain to run vertical.


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## nwbusa (Feb 21, 2012)

I'd probably use a jig saw and then clean it up with a router pattern bit.


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## Loren (May 30, 2008)

Make hollow templates carefully to make them square and 
straight-sided. I like 1/4" hardboard. You could also find
a may to make mitered templates out of thicker stock
which would get you out of filing the inside edges 
straight. Mark out the holes and cut them out inside 
the lines with a jig saw. Then use your templates and
a top-bearing flush trim bit to clean up the sides.

You could also avoid the templates and just use a
straight edge clamped to the work to trim the edges.
This method might be more appropriate if you want
the edges of the 8 top and bottom holes to come
out perfectly aligned.


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## Dal300 (Aug 4, 2011)

Use a template and the router. Depending on your router you wouldn't want to cut 3/4" deep in one pass. With my 2 HP I go that deep in 3 or 4 passes depending on the material.

When you get the holes cut clean up the corners with a sharp (SHARP) chisel or even a jig saw if you have a good one.

Good luck.

Someone else will probably come along with an easier way to do it, but this is how I've done it for years.


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## pintodeluxe (Sep 12, 2010)

Well usually face frames are hardwood, so this is a unique problem. Why do you need so much of the cabinet face to be solid, as shown in your picture? I think I would design it with a face frame, which can be easily built with a pocket hole jig.

If you need it to be built as pictured, I would cut the rough openings with a jigsaw. Then come back and pattern rout the openings to final size. If you cut to within 1/16" of your layout line with the jigsaw, you should be able to clean up the cut in one pass with the router. The pattern for the router can be built from scraps. Just make a square or rectangle, and screw it together with pocket hole screws. A bearing guided router bit will ride the pattern for a perfect cut. Leave the corners rounded, or square them up with a chisel.


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## DS (Oct 10, 2011)

Mr. Ron, for me, historically, I would treat this front panel as a giant face frame. 
The Rails and Stiles could be solid wood, or, they could be banded plywood.

You could use dowells or a Kreg jig to make the joints and I'm pretty sure, you will use far less material to accomplish your desired result.

You say you need all vertical grain. I guess I don't understand why that is.
I suppose it's possible to veneer the entire front.

Then again, careful skill saw cutting gets the job done in a pinch.

Proof again that there are thousands of ways to "skin a cat".

Don't suppose you have a CNC machine-that would be a slick method too. ;-D


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## shipwright (Sep 27, 2010)

Skilsaw (sorry, circular saw) and a guide on the good side of the cut. If you wander you wander into the waste. Second would be a jigsaw but that's much slower.


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## mprzybylski (Nov 21, 2011)

I would make two templates, one for each size of hole, out of 1/4" hardboard. I'd make the non-hollow portion of the template a bit longer and put a cleat at the end then I can butt it up against e edge of the panel and know that every square will end up being the same distance down the panel. Line it up to some vertical lines to line up the width of the template. Before doing this I'd cut a rough opening with the jig saw and then apply the template, clamp/double sided tape it to the piece and rout the perfectly square portion then go back and chisel out the corners for a perfect square.


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## tierraverde (Dec 1, 2009)

What am I missing here?
A Bosch jigsaw will fly through that, and no corner work is necessary.


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## AandCstyle (Mar 21, 2012)

Lay out the piece of plywood with extra width. Cut it into strips on the TS corresponding to the sides of the openings. Crosscut the strips that need to have the openings to correspond with the tops and bottoms of each opening. Glue the strips back together in the correct order and use biscuits or splines to strengthen the joints. Clear as mud?


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## OggieOglethorpe (Aug 15, 2012)

I'd use a router, templates, and the smallest spiral bit I could find. If you make the templates right, they can be indexed against the top and bottom edges for perfectly straight holes.

The spiral bit will leave a perfect face, the templates support the shear, and the smallest diameter will leave the least corner cleanup. With a small bit, there's no reason to precut holes. Think "RotoZip"...


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## tierraverde (Dec 1, 2009)

Jonathan,
I disagree with all of it.
In order of your statements:
1. Draw the lines, it only takes a 1/2 hour for that whole piece.
2. I know how to tilt a saw, but drilling a hole take seconds.
3. I can "walk" the saw into every line/corner from the original first cut.
4. No blade drifting with a good, modern, jigsaw (Bosch) and I think you meant perpendicular (not flat)

Please explain the table saw method, as I'm trying to understand how this can be done accurately without seeing the underside, as well as over cutting the square at the bottom.


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## RogerInColorado (Jan 18, 2013)

I'm in the router with a template, template guide and spiral bit camp. The cut will take a whole lot less cleanup


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## runswithscissors (Nov 8, 2012)

I think Art, and a couple others, are on the right track. Make it a face frame in the usual way, but using plywood boards rather than solid. I had a scheme something like yours in mind when I made my workbench. But after I got everything marked out (I think I even had started making some of the cuts), I realized I wasn't going to have a lot of plywood left, just a lot of holes. So I did ordinary face frame. Your horizontal pieces can simply be made as crosscuts on the plywood, giving you the vertical grain (But I, too, am not sure why that matters to you). Also, you'll be left with a fair chunk of usable plywood. And biscuits work very well for joining in that kind of structure.


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## tierraverde (Dec 1, 2009)

Jonathan
I thought you might explain the table saw method for those of us without the experience.


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## waho6o9 (May 6, 2011)

Plunge saw like a Festool, or a home made version.

Clean up as needed, easy peasy.


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## TerryDowning (Aug 8, 2012)

I agree with Paul M shipwright.
Plunge cut with circular saw using a straight edge guide on the good side.

finish the corners up with a jig saw or hand saw.


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## helluvawreck (Jul 21, 2010)

I'd cut it with a jigsaw and then make a pattern to tru up the openings with a router that has a pattern following bit with guide bearing.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com


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## tierraverde (Dec 1, 2009)

I really like the idea of a plunge cut saw with the rail. But not many folks have access to one. But it certainly makes sense. The plywood face is up, so you can control the cut lengths.

Still waiting for a reply from Jonathan on how he would plunge with a table saw. I know you could attempt it like sawing a zero clearance insert, but I'm wondering where you would know where to stop to avoid over cutting the corners.


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## waho6o9 (May 6, 2011)

One should not do this procedure on the table saw.


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## MrRon (Jul 9, 2009)

Thanks all. I have done this kind of cut using all three methods in the past, except for the router method which was on thin material. I was happiest with the router method as it made the cleanest cut. I'm just concerned with the bit. I'm guessing a 1/4" upcut spiral bit would be best, taking 3 incremental depth cuts.


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## tierraverde (Dec 1, 2009)

waho6o9

I couldn't agree more, but I'm waiting for jonathans explanation to enlighten the inexperienced.


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## waho6o9 (May 6, 2011)

Understandable.

I'm trying to prevent a kick back or worse….


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## Loren (May 30, 2008)

Of course you can just nail a crude frame to the back defining all the
holes and use that as a giant template for routing it out.


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## MrRon (Jul 9, 2009)

Thanks all. I have done this kind of cut using all three methods in the past, except for the router method which was on thin material. I was happiest with the router method as it made the cleanest cut. I'm just concerned with the bit. I'm guessing a 1/4" upcut spiral bit would be best, taking 3 incremental depth cuts.


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## smitdog (Aug 20, 2012)

Perhaps you could "plunge cut" with the table saw using reference marks and lowering the blade, clamping the piece in the right position then raising the blade into it with the saw running to make the cut? Kind of like making a 0 clearance insert? Seems like a nasty accident waiting to happen but I would love to hear a more thorough explanation! What's the secret Jonathan?


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## Billp (Nov 25, 2006)

I would just bring it to SPalm and have him cut it on his CNC ROUTER setup. Ha!


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## RonInOhio (Jul 23, 2010)

I agree that unless you have a really good jig-saw your cuts will likely not be 90 degrees. Just my experience.
I probably would use templates/guide with a circular saw w/good blade, and finish up with a router in several passes.


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## sprucegum (Dec 6, 2012)

If I were doing it I would lay it all out with some good dark pencil lines, put a good quality carbide tipped plywood blade on my best circular saw , hook the guard up out of the way, and make plunge cuts with blade at full depth (easier to stay strait that way). I would do this with the sheet suspended between to good solid horses and move the sheet as needed to avoid cutting them in two. After all of the cuts were made I would finish the corners with a jig saw. I am sure this is not the safest way to proceed but after 45 years of experience with circular saw I am very sure of my ability. Having said all of that you better use one of the other ideas.


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## TeamTurpin (Oct 3, 2012)

If using the router, jigsaw or circ saw methods on saw horses, I'd make some sort of jack to firmly support the cutouts from underneath. Pieces that big will make a mess falling out.

If your knees and back can stand it, this might be a good project to cut on the floor on top of a piece of styrofoam/ridgid insulation.


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## sprucegum (Dec 6, 2012)

If you leave the corners they will not fall until your are ready. A scrap board screwed to the top of the waste and overlapping the face frame works well for support while finishing the corners, that is how I do my sink hole cutouts in laminate counter tops.


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## MrRon (Jul 9, 2009)

I have a Bosch scroll saw, and I may go that route or I may go with Jonathan's method of raising the blade through the plywood with start/stop marks on the fence. I've done this before with no problem. It has the potential of being unsafe, but it can be done if you are careful. This last method will ensure a perfectly straight cut. I checked the price of a spiral upcut router bit and $38 is more than I want to spend for a one off job, especially since there are other ways to do it with the tools I already have on hand.


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## muleskinner (Sep 24, 2011)

Plunge cutting this project, which appears (from OP drawing) to be full and half sheets, on a table saw seems like a recipe for disaster. A saber saw or router are much easier to finesse than a full sheet of plywood on a table saw.


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## oldnovice (Mar 7, 2009)

I am with *nwbusa*, jig saw and router.

Or, since I was recently given a *Rockwell VersaCut* I would use that. I am impressed how well this tool really works and since it is a plunge saw it is perfect for this application! A benefit is that it only has. 1/16" kerf.


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## Grandpa (Jan 28, 2011)

I have done it on a table saw saw as described above. I think a good blade on a circular saw is just as good and safer but you can have wood splintering unless you devise a zero clearance shoe.


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