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As a beginner in woodworking I would like to build a simple box from plywood. The edges will be simply glued butt joints which means they need to be straight and smooth. When I use a hand saw I can't quite get it to go along the line and it can veer off a bit. I can compensate by sawing a bit further from the line but sanding down the excess seems to take longer then would seem reasonable.

Given that the cut lines I drew are accurate, what is the best way to accurately cut a rectangle or square from a plywood sheet with unpowered hand tools? Are there other tools I will need beyond a hand saw and a sanding block?

Edit:

To cut the plywood I am working with a two sided Japanese pull saw. Similar to the following picture.

ryoba saw

For short lengths I can make reasonably accurate straight cuts. The problem occurs when I want to make a 50cm-100cm straight cut. I have a lot of patience so speed is not an issue. Mainly I am asking how people did this sort of work before they had powered tools. Am I using the wrong saw? Should I be using guides? Should the saw just be used to get close and a wood chisel is used to remove the small excess?

  • Related: diy.stackexchange.com/q/25386/2815 – RedGrittyBrick Mar 27 '15 at 13:51
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    Echoing the answers that say, "practice". Some people like two hands on the saw; others one. You might discover that gripping the handle at the end (as opposed to being close to the blade) works for you. Experiment. Once you're cutting very close to the line, you might try scoring the line with a utility knife to minimize splintering on the topside. (A knife line isn't helpful if your cut is way off it, though.) Also wanted to note that you should use the side with coarse teeth if you aren't already. – Aloysius Defenestrate Mar 27 '15 at 13:58
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    This would have been a good question for woodworking.se, unfortunately I think it's only in private beta. – Tester101 Mar 27 '15 at 18:35
  • The description for this site included DIY which is what I consider this project. However I would not complain if this question is moved to woodworking.se in the future. – cspirou Mar 27 '15 at 21:01
  • A miter box seems like it would help. – zwol Mar 28 '15 at 4:01

12 Answers 12

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First off be aware of a couple of important points.

  1. In the old days before there ever was electricity and power tools crafts persons could build amazing things out of wood with hand tools alone.

  2. Woodworking, similar to any other craft, takes patience and practice.

  3. Plywood material such as you are proposing to work with is a modern thing invented in the age of power tools.

So yes you should be able to achieve your goals with hand tools if you take your time and work carefully. If you find any step of the process not going quite right slow down and practice till you perfect the skill for that process.

You should be able to cut the plywood with a good sharp handsaw. Plywood is a challenge though because you are simultaneously cross cutting some of the wood layers and rip cutting others. Hand saws are typically optimized as a cross cut (across the grain) or a rip (with the grain) type saw.

To get the best smooth cuts on plywood most folks will find that a power saw equipped with a carbide tipped blade will do the best job. This could be a portable circular saw if you measure for and setup a straight edge guide to run the saw base against you can end up with very good cuts.

The downside of hand cutting plywood is that you will invariably end up with a fairly rough edge. Sanding to get it smooth can be done but sanding has its problems because you can end up with a non-straight edge that may be rounded off. A hand plane may be a better choice but plywood is also a challenging material to hand plane and it is easy to get edge splintering when planing plywood in this manner.

  • I agree that plywood is a modern material. However it is my understanding that there are certain Japanese style hand saws that are ideal for cutting plywood which is what I am using. Plus I believe the problems I have outlined are not unique to plywood and would occur when cutting any large sheet of wood. – cspirou Mar 27 '15 at 12:12
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    A good jack plane (hand plane) is the "old fashioned" way to get a straight and true edge when starting with either an imperfect piece or a speedier and less true method of cutting. As Michael said, you will need to set the blade very shallow to avoid splintering. – Jeff Meden Mar 27 '15 at 15:35
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Cutting shallower (with the handle closer to the work) will encourage the saw to cut a straight line. Cutting steeper (with the handle up high) gives you more maneuverability.

Start the cut being careful to keep the blade in line with the cut. As you cut deeper, lower the handle to about 30 degrees. The blade will want to keep cutting in the same straight line that you've done so far. If you start going off the line, bending the saw to one side (slightly!) will cause the cut to start moving in that direction.

If you have some scrap plywood, I'd recommend doing some test cuts to see how it feels to cut straight and how bending affects it.

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    Basically you want to groove the wood along your cut-line before you bite deep into it. The groove will guide the saw as you make the deeper cut. Also when cutting the groove you have a longer length of saw to align with your cut-line, improving your accuracy. – Arluin Mar 27 '15 at 14:56
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I've never used a Japanese-style saw, but have always found it easier to keep a long cut straight with the rigid blade of a tenon saw than with a carpenter's saw. Held at a fairly shallow angle, a tenon saw can make an indefinitely long cut in material up to about 12mm thick.

Then finish with a jack plane with a very sharp blade set shallow.

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I have found that the stiffer the saw blade, the more accurate it is at long push/pull cuts. You are probably getting a lot of bend when you push the saw back into the plywood. My two sided saw is somewhat flimsy and so I found the following process really helps.

  1. Cut only on the pull
  2. Slide the blade back in, do not cut.
  3. Cut again on the pull

It is slow and requires patience, but that's the point of hand tools is to live in that moment instead of using power tools.

Final thing I will say is that plywood can dull the teeth of a blade very quickly due to the glue. So don't push too hard, let the blade cut as much as it wants to.

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I have a large t-square designed for doing drywall work, but it's great for many other things. I think the long side is about 4-5 ft long. Use that as a guide. It's great not just for cutting, but for layout as well.

Something like this

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Japanese saws like yours often have very thin blades which are not very rigid. Therefore, they don't respond well to the torque that's required to correct a cut that's going astray. Using a more rigid saw would be better for straight cuts.

Another idea: in some Japanese saws, the teeth are offset to one side only. You could use one of these with a metal guide, as others have mentioned, and presumably it would not damage the teeth. This is not really what these saws were designed for, but I think it would work.

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Traditionally, to dimension wood accurately with hand tools is a multi-step process. First you saw; then you plane. To make a straight edge along the grain you would typically use a jointer plane, or a jack plane tuned like a jointer (to make a relatively fine cut). To make a straight edge on end grain you would typically use a "shooting board" to keep a jack or miter plane square to the board.

If you practice sawing a lot and use an appropriate saw for the task, you can keep the planing fairly minimal, so sawing well is important. But a good hand saw cut over a several-foot cut might get you a tolerance like 1/16" or so, then the plane brings that down to thousandths if you want.

The problem with plywood is that it's hard to plane it because the grain goes in multiple directions and the glue can dull edges quickly. You may be able to do it, but might want to learn to plane boards 4-square on solid wood first.

Plywood also tends to splinter both when sawn and when planed.

There's a useful concept "coarse, medium, fine" that Christopher Schwarz explains in a video by that name, that happens repeatedly with hand tools; many operations are multi-step with rough dimensioning (using a tool that's fast but coarse tolerance) followed by fine tuning (using a tool that's slower but more accurate). This is how hand tools are able to be both somewhat efficient and precise enough, by having separate steps for removing most of the material and then for refining.

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Jig your saw into submission. Use (two) known straight edges of available material to constrain your saw. See this video on YouTube for the method:

https://www.youtube.com/watch?v=NuFb4k8Mh9Q

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best way to accurately cut a rectangle or square from a plywood sheet with underpowered hand tools

I would say the best way is to use power tools. At the bare minimum use a guide - clamp 2 straight boards on either side of the cut with a gap just wide enough for the saw. Aluminum angle works well - it's straight, hard enough that the saw won't wander into it, soft enough not to ruin your saw.

Plywood is a modern product, the grain alternates 90 degrees between layers, and it contains a lot of glue. While handsaws can produce straight cuts (and, in fact, have produced excellent results for centuries) they don't do so well when the material isn't uniform. The wood we had in the days of Louis XIV was old-growth timber carefully chosen for it's best qualities, the wonkier stuff went into the barn or the fireplace.

A circular saw with a guide and/or a couple of clamps (or just some practice) works very well on plywood, and is readily available for under $100.

If you really, really want to continue the old-fashioned way then you need to completely embrace the old fashioned way, and that means not using manufactured materials designed in the age of power tools. Or adopt a hybrid process - I assume you are using plywood because it's a LOT cheaper than large slabs of select, kiln-dried quarter-sawn cabinet-grade red oak, so use the table saw for the straight cuts and the hand tools for everything else. You will spend less on saws this way too, as the glue in the plywood is a bit rough on a plain steel blade - that's why carbide-tipped sawblades are so popular.

  • While I appreciate the answer, the question is specific to unpowered tools. I realize that there are many tools available for accurate cutting but it's not the path I decided to take for woodworking. If it is not possible to get the desired accuracy with hand tools then I think a better answer would be to explain why this isn't possible. – cspirou Mar 27 '15 at 12:04
  • I think longneck already did explain that to you. Just due to the makeup of plywood, it's very difficult to cleanly cut at low speeds without causing splintering. Keeping it straight is the least of your worries. Perhaps what you could do is clamp a level or straightedge along where you want to cut and saw against that, not sure how well it will work. You may need to rip the wood a few inches wider than you want, then go back and carefully cut to the size you need. – amace Mar 27 '15 at 12:25
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    @cspirou ask and ye shall receive. Also keep in mind that sometimes the answer to "How do I do this" is "Don't do that" – paul Mar 27 '15 at 14:13
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    @cspirou I feel like if you desire to not use power tools for your woodworking, you should also not desire to use modern wood products (plywood) in your woodworking. – guitarthrower May 11 '15 at 19:23
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I'd suggest that you get angled metal L-brackets. Clamp these on both sides of your cut line such that the saw blade fits between them.

This will keep the cut to a tight line. The closer the clamps the cleaner the cut, but also the more wear on your saw, potentially.

Widening the clamps will allow more stray in your cut (deal with that with planing and sanding) but be less wearing on your saw.

  • Pushing a handsaw between metal brackets is a sure fire way to knock the points off and the set out of the teeth. – Michael Karas Mar 27 '15 at 23:47
  • aluminum brackets and steel saw should mitigate that. You'll definitely have drift that needs to be retouched by sander and planer.... You could use as easily use hardwood guides though those will be trickier to clamp effectively – Matthew Mar 28 '15 at 2:51
  • Even aluminum guides as you describe will degrade the precision ground and set teeth of a high quality hand saw. For a cheap handsaw this would be a death call. – Michael Karas Jun 24 '16 at 6:22
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Are you using the wrong saw? Yes. I have no idea what yours is for; felling trees? After practicing with that, these should be a cinch:

Carpenter's Cross Cut Hand Saw:

enter image description here

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I used a sharp blade like an exacto knife (It was actually a chip carving knife) Worked like a charm. Not sure how thick your plywood was, but mine was only 1/2 cm thick so it took no time at all and gave me a great clean detailed edge.

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