Paul's dovetail layout
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- This topic has 13 replies, 4 voices, and was last updated 6 years, 2 months ago by David B.
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Hello,
I’ve tried multiple time to understand how Paul managed its layout as shown in the “A Paul Sellers Dovetail Technique – Episode 1 & 2”.
But I can’t seem to grasp the formula to use and succeed in creating the layout. Maybe because I’m french, and so I didn’t learn how to use imperial unit.
Anyway, can someone help me on this one ?
Are you talking about how he plotted the 8 dovetails across a length of wood? That was just a matter of angling the ruler so that the 12″ “hypotenuse” that the ruler creates when laying it from end to end can then allow you to mark the mid-points of each dovetail so that they are equidistant. It wasn’t so much about laying out dovetails as it was about using a geometry trick to get the spacing right.
Unless of course you are referring to a different video?
22 February 2017 at 2:50 am #309431For those of us, or just me, that are slow to understand, would you try to explain it again. My board is 5 inches wide, 11 inches long, and I was wanting 5 tails. So confused.
So in the video, Paul says that he wants 8 tails on his board. He places the ruler from one end of the board in a diagonal that hits the ruler at the 12″ mark. In order to make 8, he needs the center of each to be at 1.5″ increments on a 12″ ruler (12/8 = 1.5). But the board itself isn’t 12″ wide so the actual centers of the tails will be less than 1.5″ apart. Paul doesn’t need to figure out the exact distance because the angle of the ruler solves the math problem geometrically. By marking the ruler at 1.5″ increments and then dropping a line straight down to a square line across the width, he can then measure to the right and left of the centers to mark the right and left sides of each tail.
Not sure if I explained it well enough but watch the first 8 minutes again and see if it makes more sense now.
https://woodworkingmasterclasses.com/2016/04/dovetail-technique/
22 February 2017 at 5:31 am #309433You added one big factor I didn’t pick up before, the width of the board being less than 12 inches.
Ok, let’s see if I do really understand it. Since my board is 5″ wide, and only 11″ long, I can’t come up with a 12″ ling either way.
So, I can? measure 6″ down and 12/5= 2 3/8″, measure 1 3/16″ (divided 2 3/8 in half because I divided the 12″ in half to 6″) across, and move those marks up If i figured right, that worked on the 5″ wide board.
If I got it right, Thanks for all your help. If not, ?
- This reply was modified 7 years, 1 month ago by 5ivestring.
OK, after doing some practice and re-watching it is important to point out that the marks you put on the board will be the center of the PINS, not the tails. But the trick is the same and determines the number of tails–it does not matter how long your board is (11″ is irrelevant)–you are just trying to get the spacing right to have 5 tails on a 5″ wide board. You don’t need the ruler trick for this because 5″/5 tails = one center point at each 1″ mark. It is not important whether you use imperial or metric–what is important is that you set the ruler at an angle that makes it easy to do the math to figure out where each center will go. You could use 250mm and divide by 5 to get 5 (meaning each pin’s center will be at increments of 50mm).
You also ultimately determine the width of your tails–the ruler doesn’t do this for you. So once you have the pins marked, you measure an equal distance to either side of the midpoint (and importantly you measure in 1/2 of a pin’s width from the edges of your board…I will try to do a step-by-step visual of this later today and hope it will make more sense.
So, you have a 5″ wide board and you want 5 dovetails. Well that is easy b/c 5/5=1 so you would mark the center of the pins at each 1″ interval. Instead, I’m going to draw a hypothetical board that isn’t exactly 5″ so that it better illustrates that it is just a geometry trick and the actual measurements aren’t important b/c they will take care of themselves if you measure your marks accurately and precisely.
I purposefully made my board an odd width that is not easily divisible (It was actually an arbitrary distance). So here is a board that is 6 1/8″ wide. If you were to do the maths on that, divided into 5 equal parts would give you 1 9/40″ (1.225″) spacing. Not sure about you but my rulers lack those markings. So instead we simply use the triangle to find a diagonal length across the width that is easily divisible by the number of dovetails you want. I found that 200mm fit well at a certain angle so I marked the center of the pins at each 40mm increment (photo 1).
After marking the points, I draw lines straight down to the edge of the board (Paul used a line that was 1″ inside the edge so he could have some overhang I believe). You don’t need to draw these lines–you just need to know where the marks hit the edge of the board so you can mark your dovetails. Once I have the centers of the pins known, I measured 5mm to the right and left of each point as well as a 5mm mark inside of each edge as these points now represent the outside edges of the pins (as well as the tails you will see). See Photo 2.
Finally, using your dovetail template or sliding bevel or whatever you mark them with, draw the corresponding lines. I always remember that the first line from the edges goes towards the center of the board and then just draw the same line on every other point you just laid out. Then do the same from the other side of the board. Voila, a 5 dovetail template (photo 3). Note what is waste and what is to keep! Disregard the 2 extraneous lines on the right side (I decided my angle was too sharp).
- This reply was modified 7 years, 1 month ago by David B.
- This reply was modified 7 years, 1 month ago by David B.
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You must be logged in to view attached files.23 February 2017 at 1:54 am #309483Thanks, I do think I understand it now. I understand about the points being center of the pins, and measuring to each side for the tails. And if I understand more correctly now, it isn’t so important what the length of the angled line is, you just find something that is easily divisible by 5 (or how many tails you want). Then mark your points and transfer them to the straight line.
If I got it Thank you very much. That was a lot of work you went through to explain it. You also did a very good job of explaining things.
Gary
- This reply was modified 7 years, 1 month ago by 5ivestring.
8 March 2017 at 7:13 pm #309926Thought you might like to know. I used the layout technique as you explained it, and just finished the most perfect set of dovetails I have yet done. It was so much easier, and much faster, not to mention a perfect layout.
Give your self a pat on the back for explaining the technique so well.
Thanks, Gary
Just wanted to resurrect this thread since Paul did such a great video today explaining the process, as well as how to modify it a bit. Hopefully it explains it so all understand it is just a great ruler trick to get perfect spacing/sizing on a board that may not have an easily divisible width…
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