Use Dividers for Quick & Easy Dovetail Layout – No Measuring

I’m in the midst of making a place to put my woodworking stuff, a la Christopher Schwarz’s “The Anarchist’s Tool Chest.” The picture at left shows my dire need for just such a receptacle. (And it perhaps also shows a need to cull my collection.)

It’s the same chest build Chris is teaching to a full house of students right now at Roy Underhill‘s The Woodwright’s School in Pittsboro, N.C., and although we started on the same day, as Chris’s blog reveals, the students are well ahead of me. (I’m guessing they’ve had fewer meetings to attend in the last few days.)

This chest, when finished, will be painted on the exterior (likely a slate blue – which will surprise exactly no one who knows me), so the dovetail joinery won’t show. And, I want it to look sturdy and rugged (and actually be sturdy and rugged). So I elected to lay out big tails and fairly big pins rather than fuss around with delicate and refined.

I’m gang-cutting the tails (which is why I’m going tails-first on this one) because even though they’re large, there are still a lot of them. I might even be brave enough to “gang cope” the majority of the waste before separating the two tailboards for chopping. Maybe.

But no matter what size tails you like, I think it’s easiest to lay them out using two sets of dividers – it’s a lot faster and simpler than measuring the layout on all four ends of the tailboards. Plus, as long as you don’t adjust either set of dividers after you’ve determined the spacing, all of your dovetail layout will match perfectly (something that’s a challenge to achieve when using a tape measure or rule). I make no promises, however, about perfection once the sawing starts.

I used a pencil to mark the tails, because I find it’s a waste of time to bother knifing in whichever part of the joint you choose to cut first. When I transfer to the pin board, then I’ll grab my marking knife.

While we’ve written about this dovetail layout method several times over the years, until I actually saw it done, I didn’t really get it. So I’ve filmed a short video to show the method. Apologies for the several title cards and words. I was planning a voice over, but one of the cats kept meowing in the background (they love to play in the shavings pile when I’m in my shop/study). So instead, you get guitar music (because I’m not cool enough for the banjo).

— Megan Fitzpatrick

And…I’ve shot another (longer) video. I’m calling this one “the director’s cut,” because everything is in it, soup to nuts (as Chris would say). Nothing on the metaphorical cutting-room floor. Might want to grab a cup of tea first.

46 thoughts on “Use Dividers for Quick & Easy Dovetail Layout – No Measuring

  1. Barquester

    I sure am glad I tracked this down and reread it.
    That second video cleared up a lot of misconceptions about half pins. I had thought they were supposed the be as wide as the inner pins, yet you are making them much bigger. Much better for a tool chest. I think I may have been trying to make them too small even on small boxes.

  2. Nikk

    Thank you Megan,

    today I was going nuts how to layout my dovetails. I tried around for some hours and it didn’t work out.
    At lunch I thought I should look at popwood and there it was!
    You made my day!

    Regards from Germany
    Nikk

  3. MikeHenderson

    That’s a very old technique for marking out dovetails, probably reaching back to our earliest woodworking ancestors. In fact, Rob Cosman teaches that technique in his DVD on making dovetails. You can use a ruler to mark out the half pin, rather than a set of dividers, so you really only need one set of dividers for layout.

    It’s a very technique for laying out evenly spaced dovetails.

  4. BPKeyes

    Megan – I decided just to watch the second video, since I’m new to dovetails. It was perfect – clearly shown and explained. I might actually go out and try it! Thanks so much.

  5. chopnhack

    Thanks Megan!! That was really awesome to see, very simple and elegant. To read about… not so much :-) Thanks for making the video and good luck with the rest of the chest.

  6. ColH

    Hi Megan It would be far easier using a Gifkins B jumbo jig.
    No need for measuring or marking out, cuts timber up to 22mm thick and 480mm wide, very easy and simple to use on any length timber. Less than 20 minutes to cut all joints using the router bits supplied with the jig on any router table.

  7. milesthom

    Please – redo the video. Watched the it twice and could not figure out how the pin width was set. You’re not showing the whole process, and the second half of step 4 (above, walking back from the other end) is critical.

    Cheers – Miles

  8. Barquester

    The title (no measuring) leads us to believe that you divined the tails width by means other that a rule. So how does that work?
    Would not hermaphrodite calipers be better for the half pin layout. Heck, a mortising gauge would be better than guessing where the edge is.

    1. Megan Fitzpatrick Post author

      Divined only by what looks right, really – as long as it can be stepped off along the edge and give you a pleasing pin width.

      I’m sorry – I don’t quite get what you mean about guessing the edge? You can just hold the point of caliper 1 at the edge (you might be off by a 64th or so I suppose (but the problem would be the same with the pins on a mortifying gauge, no?)

  9. andrae

    I had never used dividers until I started practicing hand dovetails. I think it’s a great way to work. Then building the tool chest caused me to acquire a small collection of dividers to reserve the various dovetail spacings and other measurements. I gang-sawed and gang-coped. I didn’t mess up any more than I would with a single board, so I say give it a try, you’re surely better than I am. I stopped and redirected further from the baseline when I got nervous.

    Peggy: I used federal blue milk paint and like the color. It’s more cheerful than the dark, dull shades I’ve seen on most tool chests.

  10. TomHolloway

    As I understand it you use this whole procedure, including the many placings of the template, for all four ends of the tail boards. I do something similar one time, complete the first set of tails, then use that finished set of tails as a template for marking the tails on the second board with a single placement of the template. When those are cut, one end of the second board becomes the template for the other end of the first board. This means much less freehand placing of dividers and angle gauges, and consistency on all 4 corners. Pins are still marked (with a knife) from the tails they will match with.

  11. Peggy

    I’m going to paint my tool chest federal blue (not a surprise to anyone who knows me, either), if I ever get it done.
    I would have enjoyed cat meows as background music, especially Siamese!

  12. Planesaw

    Megan,
    Like you, I have seen this but didn’t “get it.” This is very helpful, but I am still with Travis (above) with the question, exactly where did you start in/on the half-pin with your 2nd set of dividers? If it doesn’t matter, just anywhere on/in the half-pin, then shall I assume (dangerous) that the pins will not come out “centered” or will come out closer to one end than the other? BUT, I may be getting it — when you start anywhere in the first half pin, are you just marking one side of the pins? And, then when you start in the other half pin to go back the other way, are you then marking the “other” side of the pins? Therefore, they are coming out uniformly? Hope this makes sense. Alan

    1. Megan Fitzpatrick Post author

      See? Much easier to watch it done! And clearly, I should have shown the entire process. No – you don’t start just anywhere in the half pin – you start in the pin hole.

      1) With the divider that is set for the half pin, place one leg on the narrow edge of the board at the very end along the top, and make a pin mark where the other leg hits (typically somewhere in the 1/8″ to 1/2″ range – whatever you want that half-pin size to be). Do the same at the other end. Those marks denote where you’ll mark the start of the first tail (and start in either of those two holes for the next step.

      2) Now, set the second set of dividers to the approximate size you want your tails to be, with the understanding that you’ll likely meed to make an adjustment or two before you decide on a final size. Drop one leg in one of the half-pin holes already marked on your top edge, then walk the dividers down the top edge, without pushing the points in, until you cross the second half-pin mark already on the edge at the other end. When you get to that last “step,” whatever distance is between the leg of the divider that’s closest to the end and the marked half-pin hole, is the size the top of your pin will be – in other words, that denotes the gap between the tails. If it doesn’t look right, e.g. you’ve gone too far over that half-pin mark so the gap is too bucky, or you can’t cross it at all without falling off the end of the board, adjust the second set of dividers in or out (out for fewer tails or to make a larger pin, in for more tails or a more narrow pin – it may be a big or small adjustment.) It’s trial-and-error, of sorts – but one small adjustment adds up over the entire width!

      3) Now repeat. Once you can walk from one half-pin mark down the board and cross the second half-pin mark with a pleasing gap in between the leg and mark, you’ve got your setting for the second set of dividers.

      4) Drop the divider leg in one of those half-pin holes, and walk down the board but this time, press down with the point at each half-turn of the dividers as you go to make a mark. As you cross the half-pin mark at the other end, don’t push down. Instead, lift the dividers and drop a point into that second half-pin mark, then walk back the other way, pressing down with each half turn. The end result is two pin marks at each tail, spaced in between by the distance you established in step 3.

      Line up your gauge with those marks to mark the extents of each tail, and you’re ready to saw. And when it’s time to move on to the next board, there’s no trial and error. Simply mark the half-pin holes off the setting on the first set of dividers, then use the second set to make the marks.

      Hope that makes sense.

  13. Steve_OH

    I sometimes mark out dovetails on a story stick of appropriate length, and transfer the tick marks from the stick to the board ends. That way, I’m better assured of consistency from one set to the next, even if I knock my dividers onto the floor, or a ferret runs off with them, etc.

    -Steve

    1. Megan Fitzpatrick Post author

      Sorry…didn’t want to bore with the moving up and down. Leg starts in half-pin hole on the far end, and walks down to cross other half-pin hole – then lift, drop point in near half-pin hole, and walk back the other way to define the other side of each tail.

      1. B Jackson

        … and what they’re not telling is, you can make one for yourself out of, say, 50 cents worth of stuff from your scrap bin … Sorry, Megan and guys, but sometimes the truth, the whole truth, and nothing but the truth gotta get out there …

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