Mar 08 2012

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Magnetic Saw Guide

Last month, I watched an excellent video by David Barron called “Hand cut dovetails made easy.” His whole technique was excellent and it was easily the best demonstration for cutting dovetails I’ve seen yet — it made me feel like a hack for posting my dovetail slideshow. This first time through, I took two solid tips away from the video: back cut (around 92°) when chiseing the waste from the base of the joints and use a saw guide when making your cuts. I’ll probably end up watching it several more times though.

I had always thought saw guides were for beginners, but seeing David use one got me to thinking that I could make one very easily from materials I already had in my shop. Grabbing some scraps of 3/4″ MDF, I squared them up on my miter saw and glued them together at right angles to form the guide. Once the glue dried, I went back to the miter saw to square up the ends.


Since I was using a pull saw, I oriented the guide so it rested against the back of the board — the cutting stroke will pull the guide into alignment. Since I’m right handed, I drilled the two 1/2″ holes for the magnets on the right side of the guide. I tried to drill them so that the magnets were right below the surface, rather than flush so only the soft MDF would rub against the saw not the hard magnets. As you can see from scratches on the magnets in the first picture I didn’t quite drill the holes deep enough the firs time.


The two magnets hold the saw pretty firmly, so when you line up the cut you need to do it with the saw stuck to the guide. At first there seemed to be more much more resistance when sawing, but then I figured out that the set of the teeth was wider than the body of the blade, and I was cutting into the MDF, as you can see in the first picture. After a few uses, when I wasn’t also cutting the MDF, I really didn’t have to exert much more force to overcome the magnets when sawing.


I made the cut on the left free hand while I made the cut on the right using the guide. If I had a line to follow, I’m sure I would have made a much straighter cut, but if I use the guide, I might be able to skip a few steps during layout saving time. I don’t show it, but I checked the cuts with a square and the cut I made with the guide was dead-on.


Another interesting effect of using the guide is that the cut is much crisper. As you can see from the cut on the bottom made with the guide, the guide stopped me from swinging the saw side-to-side as I made the cut.

I made several more test cuts with the guide and found a few of the cuts weren’t perfectly straight. It seemed like the deeper I made the cut the more chance there was of the blade wandering, but I think that the guide should prove fine for cuts 3/4″ deep and shallower.

Now that I’ve made a straight guide, I am in the process of making a guide with a 1:8 pitch. I just need to figure out how to drill perpendicular to the side of the guide to place the magnets. The project has been put on the back burner though since I just got my new lathe.

Permanent link to this article: http://workshop.electronsmith.com/content/magnetic-saw-guide/


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  1. Tracy Hall, CalDIY

    For deeper cuts, you may want to add a magnet or two down the longer part of your guide (on the back face) – between the top magnets, and the extra hint, it shoud help…

  2. Tracy Hall, CalDIY

    I’d also note that mr. barron’s guide had a “step”, allowing it to be used *above* at the start of the cut, and deeper (by moving it back, dropping the step) for a deeper cut…

  3. Joe

    It probably wandered on deeper cuts because you were cutting a bit of the deeper part of the gude away due to the offset of the teeth.

  4. Anonymous

    Regarding drilling the hole for the magnet, David Barron uses a jig to present the guide to the drill bit in the correct position and at the correct angle – probably the the best way if you are producing them in quantity. Since I was only making a one-off for my own use, however, I took the easy way out : I cut two small pieces of thinish sheet material to the shape of the ends of the guide, drilled the holes to accomodate the magnets, then glued the cut/drilled shapes to the ends of the guide.

    Any sheet material a bit thicker than the magnets will do – I used off-cuts of cheap laminated flooring (about 8mm), but pretty much anything really. Exact shape doesn’t matter – if it’s slightly too small, it’s OK, and if it’s slightly too big, just file/chisel it down to below the bearing surfaces.

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