Finger
joints are a great joinery technique to get your hands on. You can use the joint for corners on any kind
of box, even drawers. Thanks to the huge
amount of surface area for glue, the joint is very strong. It's also an attractive joint, especially
when made with contrasting woods.
This
article will show you how to build a finger joint jig and use it on your table
saw.
About The Jig
With my
simple shop-made jig, finger joints are easy to make. The jig relies on being fastened to your
miter gauge. In this story I'm making
the jig to cut 3/8" fingers. You can
make it for any size fingers you want, just change the width of the key. You'll need a separate adjustable front for
each size of finger joint you want to make.
The backer
board on the jig fastens to your miter gauge using the mounting bolts. The oversized holes allow you to micro-adjust
the jig so the fingers fit perfectly.
The
adjustable front includes a key that registers the fingers when making a
joint. The adjustment bolts go through
oversized holes on the backer board and lock the adjustable front in position.
Making The Jig
Rip the
backer board and adjustable front to width, then cut them to length.
Install
your dado head and set the height to 5/16". I set the height using brass bar stock (see Sources) as a gauge.
The width of the
dado should equal the width of the fingers you want in the joint, in this case
3/8". No need to change how you make the
jig if you're using wider or narrower fingers, it'll still work fine. The height of the dado must be less than the
thickness of the material you'll be cutting the joint in. That'll make more sense later.
Cut a slot
in the adjustable front, located 5" from the end.
Cut a key,
and check its fit in the slot. A small
parts sled (see the story) is a safe and easy way to do this. I first plane the key board to 5/16" thick,
then rip the key. Once you have a key
that fits, cut a 2" long piece and glue it into the slot. Drill the holes for the adjustment bolts, but
only in the adjustable front. The holes
are located 10" and 14" from the key end of the jig, 3-1/2" up from the bottom.
Fasten the
backer board to your miter gauge so it's centered. I used 1/4"-20 carriage bolts, counter boring
the face of the backer board with a 3/4" forstner bit for the head of the
bolts. You may need to use a different
fastener for your miter gauge. Mark the
hole locations directly from your miter gauge.
Use an
offcut of the key to position the adjustable front against the backer
board. This will get your set up very
close to being perfect.
Mark the
adjustable bolt hole locations on to the backer board. Drill 3/4" holes through the backer
board at these two locations.T he over
sized holes allow the 1/4'" carriage bolts plenty of lateral adjustment for fine
tuning the fit.
Fasten the
backer board to your miter gauge.
Assemble
the jig on your miter gauge, again using a piece of the key stock to locate the
adjustable front board. Lock the front
in position using the wing nuts. The
fender washers are large enough to bridge the oversized holes.
Test Cuts
Set the
height of the dado head to slightly more than the thickness of the material
you're cutting. This creates fingers
whose end grain projects slightly past the face of the mating piece, which is
what we want.
With the
test board positioned against the key, make one cut.
Make one
cut in the mating board.
Test the
fit. If the joint is too tight, as it is
here, the key is too far from the dado head. Loosen the adjustment bolts and shift the position of the adjustable
front board. Continue to make test cuts
until your achieve the fit you want. The
fingers should easily slip together, but shouldn't be sloppy.
When the
height of the dado is correct the end grain of each piece should project past
the face grain of the mating piece.
Once you
have a perfect fit make an index line across the top edges of the two
boards. This will help you get a
close-to-perfect set up each time you use the jig. If you plan on making additional front boards
to accommodate different finger joints, mark the index line so you know it's
the one for 3/8" fingers.
Cutting Joints
To cut a
joint, reset the height of the dado head as needed to match your material
thickness.
Cut the
first slot with the edge of the board against the key.
Slip the
first slot over the key and cut a second slot. Now it's easy to see why the thickness of the key must be less than the
thickness of the material you're working with.
Continue
the process across the width of the board.
Repeat the
process for the mating piece.Note that
the top edge of the walnut board starts against the key, and the bottom
edge of the cherry board that starts against the key.
Slip the
joint together.You're ready for
glue!
Tips The width
of the boards you'll be joining should be in even increments of the finger size
so the joint starts and ends with a full finger and full socket. For example, the boards cut for this story
are 4-1/2" wide, an even increment of 3/8".
If you
find that you're getting a lot of blow out on the back side of your boards, add
a thin sacrificial board to the jig. I
use 1/4" plywood, held on with double faced tape.
Sources Brass Set
Up Gauges Part#
144932 Woodcraft Supplies (800)
535-4486
Jethro stated he saw this on the last dvd he recieved. I have bought the first two dvds that you had but haven't recievedthe third dvd. Is the third dvd the one with this jig.
This was such a simple jig that I am going to build it as I already promised my wife that I would build some boxes to my wife for her pantry to store spice bottles etc.
Where is the live version of the finger joint jig. You stated on the table saw techniques but where is the table saw technques DVD located. I want to see it. Please respond !
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