DIY Magnetic 3-in-1 Hand Saw Guide - Cut Straight & Square Without Expensive Tools!

For years, I struggled at cutting straight. No matter what I tried, most of my cuts didn't end up square. I tried using different saws, marking additional lines, adjusting my posture - none of which helped much.

In this Instructable, I will show you how to make a magnetic hand saw guide that holds your saw straight for you - but doesn't interfere with the cut! This is my third attempt at making one. I made an Instructable for my first simple clampable magnetic guide, as well as one for my second version, and only made an experimental video for this one since after so many partially-successful attempts, I didn't believe I would use it - but I've used it over the past two years for hundreds of cuts, and love it. This tool can be made easily without the use of expensive power tools, takes seconds to set up, is simple to use, and requires actual effort to NOT cut accurately!

(Don't want to read the I'ble? Watch the Youtube build video and see it in action!)

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Step 1: What You'll Need: (affiliate Links)

Tools:

Japanese saw - I've been using an inexpensive Japanese pull saw for years and recommend buying one to use with this guide. Push saws can't be used due to their spine, and but large crosscut saws can, though I highly recommend using with a Japanese saw: Its sharpness, the speed in which it cuts, and the smoothness of the cut are on a whole 'nother level!
Replacement saw blades - I bought 3, but they last a very long time if you're careful.
Bench vise
Bar clamps
Speed square
Countersink drill bits
Spade bit - the diameter of the magnet, or slightly larger
Cordless drill
Impact driver
Drill bit set
X-acto knife
Small hacksaw (these use very fine blades that are great for cutting plywood)
Proper safety equipment (Kit: the PPE I recommend if on a budget)

Hardware, Materials & Consumables:

3-5 25x2mm neodymium disc magnets - I got 3 from a sports wristband. DON'T buy black ceramic magnets, they are significantly weaker.
Thin hardwood plywood
Epoxy
Scrap wood crosscut to square (more about it in the next step)
A few wood screws

I made it for free since I already had everything that was needed on hand. If you want to know more about a specific tool/part that I used, need ideas for alternatives, or don't see something you think should be here, please let me know in the comments.

Approximate Build Time: 2 hours

Step 2: A Square Piece of Wood

This magnetic guide might be useful for woodworkers that use power tools, though I assume most who want to build it want to because they are unable to cut accurately enough - if they had accurate power tools they wouldn't need a hand saw. This doesn't change the fact, however, that the guide needs a square face.

For that, there is a simple solution.

If you can't make accurate square cuts (like me!), find a board that's already square. It doesn't need to be perfect: I scavenged a square leg from a broken IKEA table that had a hole so I plugged it, and made sure it was square.

There are two ways to verify this: If you have a speed square you'll be able to see if it's square easily, but if you don't, you can also try to place the board on the end grain, vertically, and if it leans to one side or falls over, find a different piece of wood to use.

Step 3: Magnets - and Drilling

Magnets are needed to attract the saw to guide it properly. They need to be inserted into the square end grain of the board, and be flush with the surface, so I drilled a 25mm hole into the end grain with a spade bit. Luckily I had one that was big enough, otherwise I'd enlarge the hole with a rotary tool or a router, as I've done before.

I actually planned on using only two magnets, but they were so strong, I was unable to separate them! Future me doesn't regret giving up, the guide holds on to the saw with just enough force.

Step 4: Make the Plywood Face

This is what the saw rubs against. It has to be a low friction material, and I happened to have some thin hardwood plywood on hand. And two years after making the guide, it hasn't deteriorated at all. I recommend experimenting with different thicknesses if you're using random magnets like me, because their grade is unknown and they might end up being too weak (if they're too strong you can always glue on thicker plywood). You can also 3d print the face, or design and 3D print the whole jig, and if you do - I'll credit you in the Instructable and send you a free premium membership to Instructables :)

Someone asked me once about the friction, and I find the best way to explain it is to analogize it to skiing. You don't need an incredible amount of force (magnetic attraction) to assist in holding the saw at 90° while cutting, and there is very little (unnoticeable) friction between the saw and the birch plywood face. To exaggerate: even if the magnetic attraction was extremely strong, it wouldn't interfere too much with the sideways/sliding friction of the saw against the plywood face - but it would make it harder to pry off the saw. Imagine yourself ice-skating. Placing magnets under the ice would stop you from being able to lift your feet, but it wouldn't interfere too much with your ability to slide on the ice, because the ice is still very smooth and the friction between your shoes and the ice doesn't increase as significantly.

Step 5: Glue

I used two-part epoxy to glue the magnets to the plywood , and after it had cured, the plywood to the end grain of the board. Wood end grain sucks up a lot of glue, so you might want to wait a few minutes for it to seep in, so you don't end up with a glue-less joint.

None of my clamps were long enough to clamp it together, so I improvised a clamp with a bungee cord, pulling against my bench vise. On my first attempt, it exploded and hit me in the face, but I didn't catch it on camera. Because that's obviously what matters.

Step 6: Make the "shelf"

If you don't want to clamp the guide in a vise, and want to just clamp it to a workbench with clamps, skip this step. But I don't see any reason to do that.

I screwed on a wider board to the side of the guide, which is what the bench vise holds on to, and the piece of wood you want to cut can also be clamped to it. I suppose you could also say it helps cut wood straight on the Y axis, but it's not that complicated.

Step 7: Last Touches

The guide doesn't have to be too long. From my experience, 30 cm (about 1 foot) is enough. So I cut the rest off.

Saw blade teeth are usually bent outwards, so the kerf (cut width) is wider than the thickness of the saw blade, so it doesn't get pinched. I try to avoid having the teeth touch the guide, but in case it ever happens, I recommend rounding over the edge of the plywood with a sharp knife.

Step 8: How to Use It - + 2 MORE Ways!

There are three ways to use it.

99% of the time, I clamp it in my bench vise and hold on to the piece of wood by hand, but if I can't afford to make a mistake, or if it's too small or heavy and I don't have enough leverage, then I'll clamp it. (Pictures 1-2).
I've also used it to cut miters by clamping it to my workbench, and clamping the piece of wood I want to cut at 45 degrees with a speed square, and the guide makes the cut significantly more accurate. (Pictures 3-4).
You can also use it as a portable guide simply by holding it or clamping it onto a board. This setup would be ideal if you want to cut 2x4s, for example. (Pictures 5-6)

Watch it in action, on Youtube!

Some more thoughts:

To guide the saw even better, you could add another face on the other side of the saw, but it would interfere when cutting, and would have to be very precise or spring-loaded, and would be prone to breaking.
For certain cuts, I also have to bend down when cutting which can be uncomfortable and slows me down. The solution for this could be to make a tall stand, or tilt the guide forward which would make it harder to hold onto boards - non of which are worth the hassle for me because I like how it's small and portable.
Both of these ideas are minor improvements with major drawbacks.
As I've written previously, I've been using it for over two years, for hundreds of cuts, and am very satisfied with the results - and recommend you to build your own! The results I've gotten from it are much better than my circular saw, as I showed in my Instructable on How I find so much free lumber.
If you don't have a guide, and have tips for cutting straight without one, please let me know!
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