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