newb question on cutting rectangle out of plywood sheet - Woodworking Talk - Woodworkers Forum
 
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post #1 of 17 Old 02-23-2013, 10:27 AM Thread Starter
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Question newb question on cutting rectangle out of plywood sheet

As someone without much woodworking experience, I have a question for the board.
I am going to be cutting a door, out of a sheet of 3/4 plywood. It will be rectangular. So two sides long, two sides shorter. My question is, what is the best (or is there a best) order to make the cuts. Obviously the fourth cut will be the last, so I wondered what order expereinced woodworkers would do that in. Or if it even would matter to them

Also a 2nd question, any tips on the best way to get smooth finishes at the 90 degree corners on this (I'm only using a power saw, don't have table or miter) type of cut appreciated too, if you have
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post #2 of 17 Old 02-23-2013, 12:06 PM
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Quote:
Originally Posted by markinatlanta View Post
As someone without much woodworking experience, I have a question for the board.
I am going to be cutting a door, out of a sheet of 3/4 plywood. It will be rectangular. So two sides long, two sides shorter. My question is, what is the best (or is there a best) order to make the cuts. Obviously the fourth cut will be the last, so I wondered what order expereinced woodworkers would do that in. Or if it even would matter to them

Also a 2nd question, any tips on the best way to get smooth finishes at the 90 degree corners on this (I'm only using a power saw, don't have table or miter) type of cut appreciated too, if you have
You will probably get a lot of good replies but you also may want to give more details. I will assume your powersaw is a circular saw. To get a good cut on a sheet of plywood the saw blade is critical but even more so is how you support the plywood, both the cutoff piece and the main piece. If there is any tendency for either piece to move/shift after being cut it will do that before the cut is finished and create a tearout at that point. Use a saw guide is a must for a nice straight cut. If the board you are starting with is new and in good shape the factory edges will probably be as straight and clean as anything you can cut with a circ-saw so I would use them for two sides of the door you are making. Determining what cut to make first is usually based on how you layout the cut and what leftover piece is more desirable. Often one cut will be easier to do due to the size of a sheet of plywood, as you reduce its size it becomes easier to manage. If the door is small such as a cabinet I would tend to layout the work so that more than one door could be made in case I mess up the first attempt.

More details and you will get some great advice from this group.
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post #3 of 17 Old 02-23-2013, 02:35 PM
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It would really depend on the size of the part you are cutting and what would be the most usable size of the wood left over. I would just use a straight edge and clamp it to the sheet and cut the door. If you use a sharp 60 tooth blade it should make a clean cut.
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post #4 of 17 Old 02-23-2013, 05:26 PM
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Personally, I'd use a saber saw to make the cuts. Drill a 3/8" clearance hole in opposite corners and saw to the lines.

It can be done with a circular saw but it's not something to do without being shown how to do it. In addition using a circular saw leaves visible waste material on the lower sides.

Howie..........
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post #5 of 17 Old 02-23-2013, 08:57 PM Thread Starter
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Yeah I guess part of the point of this question, was how to do it with a circular saw, i.e. that's all I have (that could work). As far as the other statements, there is no throw away part - the idea is I have a "side" of a cabinet and I want to cut a door, out of it. So hen finished will still use both pieces. I'm prepared to measure/draw my lines, and start the cut in the lines then go to edges. And feel that I get the whole support/binding part. What I was wondering is, what's the best order for the 4 cuts. Two are (equally) long, and two are (equally) short. Would seem like the last of the 4 cuts is critical, since that's when the 'door' will finally 'drop'
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post #6 of 17 Old 02-23-2013, 09:31 PM
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I didn't fully read your question I guess. Make three cuts then Add support on the bottom side. Keep you blade deep to minimize the length of over cut needed t free the piece

Last edited by TooTightIsBroke; 02-23-2013 at 09:36 PM.
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post #7 of 17 Old 02-23-2013, 09:37 PM
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the short dimesions are critical

They cannot be smaller than the diameter of the "exposed" blade. If that's not a problem then there is another..... You must "plunge cut" the saw into the work up to the lines ...and go in reverse! You have to had done this a few times to get it right. and it's not exactly the safest procedure using the circular saw. I could do it myself and have done it, but I would not recommend it to a novice.

Plunge cut saws like the Festool, Makita and others may be a safer way if you have one? Lacking the proper saw and prior experience I recommend using a saber saw and drilling a line of small pilot holes to start the blade. A Rotozip with a spiral up cut bit against a guide would yield a narrow kerf also. If your door could have radiused corners rather than sharp, 90 degrees, that would make the process easier and safer.

Another method I have used is to fully lower the table saw blade, then slowly raise it into the workpiece which is held securely downward and against the fence. Again experience is required for this process as well.

The Fein, Rockwell and H-F saws that cut with a oscillating motion also can create their own kerf without a starting hole.

Ideally it is possible, but in reality it's not an easy project.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #8 of 17 Old 02-23-2013, 09:55 PM
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Rail saw, easy peasy.
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post #9 of 17 Old 02-24-2013, 12:19 AM
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Cutting a door opening in the side of a cabinet I would mark a line and cut the line at the top and bottom with a utility knife so the veneer doesn't tear when you make the cut. Then I would put masking tape on the side of the cabinet so the base of the saw doesn't scratch the finish. Then I would use a 60T blade and freehand cut the hole stopping at the corners. Then the corners could be cut with a jig saw or hand saw. The piece of plywood removed could then be cleaned up and made into a door.
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post #10 of 17 Old 02-24-2013, 02:33 AM
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Quote:
Originally Posted by Steve Neul
Cutting a door opening in the side of a cabinet I would mark a line and cut the line at the top and bottom with a utility knife so the veneer doesn't tear when you make the cut.

Then I would put masking tape on the side of the cabinet so the base of the saw doesn't scratch the finish. Then I would use a 60T blade and freehand cut the hole stopping at the corners.

*** Yes but...this seems like a tricky cut for a novice to freehand. IMO (not knowing the dimensions of the material or the cut) it might be better to clamp a good straight guide (fence) to the material taking into account the distance from the edge of the CS base to the blade.

Then make the plunge cut by setting the front of the saw base to the fence while holding the blade off the material until the saw reaches full speed then plunge and keep the saw base to the fence until you reach the corner (end of the cut).

Because your blade is circular the bottom of the cut will be shorter than the top. This will leave some material at each corner that can be cut with a jig saw after all of your plunge cuts are done.

To support the outside and inside pieces cut 8 ea. 3 1/2" lengths from a 2x4, Using double sided tape place four of these under each corner of your plywood. Place the other four under the intersections of your cut line.

Set the depth of your saw blade to 1" (assuming the material us 3/4" thick).

The blade will cut into but not through the support blocks and still support the material as you work.

Once you've completed the plunge cuts move the blocks that span your intersection lines to the inside so that they're out of the way of the jig saw when you complete the corners (edit: freehand)

Note: Depending on the length of stroke on your jig saw and the length of the blade you make have to use additional blocks so that the jigsaw blade does not touch the surface of the floor or bench.
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Last edited by jharris2; 02-24-2013 at 02:36 AM.
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post #11 of 17 Old 02-24-2013, 10:32 AM Thread Starter
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Wow, all of this is sounding a lot more complicated, than my original research indicated. But thanks for the feedback
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post #12 of 17 Old 02-24-2013, 10:40 AM
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Quote:
Originally Posted by jharris2 View Post
*********
Well I originally said clamp a straight edge to the plywood but the OP said in post 5 he was cutting a hole in a cabinet. I assumed he meant a finished and installed cabinet. This makes clamping a straight edge pretty difficult. You would almost have to nail the straight edge to the cabinet and fill the hole later. It's a difficult project for anyone but if he takes his time he should be able to do it. The most important thing to do is cover the side of the cabinet where the saw base slides so it doesn't scratch the cabinet.
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post #13 of 17 Old 02-24-2013, 10:46 AM Thread Starter
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It *will* be a cabinet, but its unfinished plywood at this point.
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post #14 of 17 Old 02-24-2013, 10:54 AM
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Don't forget about "really" thin kerf blades

Quote:
Originally Posted by markinatlanta View Post
It *will* be a cabinet, but its unfinished plywood at this point.
My older Dewalt 18V battery saw as some really thin kerf blades, 5 3/8" Dia. I believe, 10 MM bore. There are others in 6" or 6 1/2" for Rigid I think. If you need a miniumum kerf all the way around than that's what I'd use. You can always border the door panel with a thin strip of veneer to close up the gap from the kerf.....

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #15 of 17 Old 02-24-2013, 10:54 AM
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Quote:
Originally Posted by markinatlanta View Post
It *will* be a cabinet, but its unfinished plywood at this point.
That would be a lot easier especially if you can turn the side you are cutting up. I was picturing cutting a hole close to the wall, floor and countertop. You could skip the masking tape then. The scratches would be very superficial which could be sanded out later. Just run your hand over the base of the saw before you get started and make sure there isn't any sharp burrs.
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post #16 of 17 Old 02-24-2013, 03:55 PM
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I didn't understand what you were doing until re-reading your posts carefully.

I would use a drill to make a hole for a jig saw blade and then make the cut with a jig saw. Not the easiest tool to use for finish cuts but it can be done. You would need a blade that is meant for making finish cuts though, preferably not an old dull one.

Do you have a jig saw? I think it is a common enough tool that most people would want one.

I don't have a plunge / track saw. They are pretty expensive and I don't think I would use one enough to buy it. Maybe you could rent one?
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post #17 of 17 Old 02-24-2013, 07:23 PM Thread Starter
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I will use both pieces, after cut, so drill is not a good option. I;ve decided I'm just going to make 4 plunge cuts with the table saw, and then finish the corners with a jig saw. After lining it all up today I'm pretty sure I can make it work. I was just short a clamp, for how I wanted to secure it, so hope to get that tomorrow, and try it. Thanks everyone
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