it's a very common question people
contact me and say what size dovetail do I need for this particular project this
size of piece of wood is there's some formula that I can use and I want to say
not definitively but there isn't really a formula there are standards that
people reach for and usually the dovetails are bigger than the pins but not
always so let me show you what I have found works for me I'm not saying this
is the only way but it does work well and I've used it for many years what I
have is a dovetail piece this is a two inch section of wood so if I put this on
its side it looks like a draw now I've got one dovetail and a two inch section that
doesn't mean that you can't put two dovetails in but generally one dovetail
is enough then I found that if I have a three inch section I can use two
dovetails in it if I have a four inch section I can use three dovetails and
that works perfectly well the size seems proportionate it seems to be a good
balance of everything I want then when I get to a five inch piece of wood I've
got four dovetails and if from there on it's getting taller and taller
say for the edge of a toolbox or something like that I just generally
stay with my dovetails not being bigger than one and a quarter and my pins being
fairly compact three-eighths of an inch ten millimetres something like that
works perfectly well so that's how I do it now then I also will use
3/8 of an inch here so I'll use 3/8 of an inch on these and that gives me a
good proportional size here as I said I would never go more than one and a
quarter generally that gives me a nice strong dovetail and the strength is
important but sometimes let me take this one and show you some alternatives here
this one I've got 1/2 pins on the outside and full pins here full pins
here but then on this side I've changed it I've got very small pins and these
are the options so it's the pins that usually dictate what size the dovetails
are or vice versa but the pins become primarily important to you so here I've
got a small pin small pin small pin small pin here I've got
fairly good-sized dovetails this would be more utilitarian it would make a
great toolbox it would make a good kitchen drawer that kind of thing but
when you get to the fine furniture generally we go down in pin size because
it looks very refined it can look a little bit prissy and I'm never sure
what makes it prissy and what makes it refined this is my favorite dovetail for
a box for a working box 3/8 3/8 and 3/8 exactly the strength I want for this
particular box I've used it for years on boxes made hundreds of boxes using that
and it works great so let's look just briefly at this
five-inch one because often you may not want these outside pins to be half size
sometimes they can be too thin sometimes they're so thin that they will split off
along the side of the pin piece and it will make it weak so I try to avoid that
so let me show you first of all how would you lay this out to get the half
pins what we're going to do is we're going to divide this five-inch piece of
wood up here now the piece of wood may not be exactly five inch it may be four
and three-quarters four and seven eighths five and 1/8 or whatever how do
you divide this up if you've got these odd numbers these difficult numbers to
divide if you're in metric it's slightly easier but you still have to divide up
that single millimetre so what we're going to do we've got five
and a quarter actually here so what I'm going to do is I put my ruler across
here and however many dovetails I want I want to divide this up into something
that will divide into four so four increments I've got four dovetails I
want this to divide into four increments I could go to 12 and divide it by three
inch increments but I can go to eight and that works fine I can't go to four
because it's too small so I make a line across here and then I make a mark on
the two inch mark the four inch mark so all I'm doing you could use any unit of
measurement for this what that does there and if I take this
line and transfer it down the length here it brings me to the center of the
pin if I go here it brings me to the center of the pin turn it round pull it
this way it brings me to the center of the pin so what happens then when I take
my dovetail template onto this line if I measure if I want say 10 millimeter
dovetails I go 5 millimeters on each side of that center line and that gives
me the size of the pin and then I take my dovetail template and Mark my lines
on here just like this flip over and I do the same on the other so that's how I
get that and what that leaves you with is equal sized dovetails but you end up
with a half sized pin on the outside what to do if you don't want that if you
want equal size dovetails all the way across including the outside or even if
you want bigger dovetails on the outside edge bigger pins on the outside is let
me show you what I would do let's say I want ten millimeter pins what I would do
is if I've already decided that I take five millimeters off this side and five
millimeters off this side and I run this line down here there's a guide there and
then I go across here from the from the pencil line this time not the edge of
the board go to that pencil line set it on to the eighth mark if you're going to
have four dovetails make your mark two inch increments again pull that down to the same here now I'm going five mill five mill I'm
guesstimating this just for speed but you'll measure it five mill five mill
take my dovetail template make my mark oops wrong way there and then I measure the 10 mil onto this
outer edge like this and that will give me equal size dovetails so these are all
now the same twenty one twenty one and twenty one so that's how I do it that's
my dovetail layout that's how you can alter the size of those outside pins and
that gives you equal dovetails and equal pins all the way through you
