I have been fascinated by the Woodgears.ca website for years.
Matthias Wandel builds fascinating gizmos, jigs, tools as well as
interesting wood projects, and posts new items regularly.
In particular I have been thinking about building a version
of his Screw Advance
Box Joint Jig
for a few years now. Not that long ago I decided that I would try and get
started on it over this Christmas holidays as a present to myself.
And of course if I'm doing that, a photo essay here was almost
If you want detailed build instructions, please go to his website and
read his web page, and/or watch his instructional videos, and/or buy his
plans -- they're quite inexpensive. My intent here is to just post
some photos of my own build, with a focus on what I did different, or
areas where I had particular challenges, or anywhere that I thought his
plans needed a little elaboration. So I will NOT be posting detailed
instructions or plans here, and if you are not familiar with his jig you
will likely not understand what I'm doing!
Note that I wrote this document while I was building the jig,
so this is mostly written in the present tense, and with no knowledge of
what is coming up next.
Building The Jig:
I actually got started a few months ago when I bought the
Box Joint Cutter
set at my local tool store.
The blade has a good reputation in various
online forums, and was also recommended by the guy at my store (whom I
Now, curiously enough, Matthias actually uses all kinds of different blades
with his jig -- none of which, to my recollection, are actually
purpose-designed for box joints. So I hope this will work out, we'll
The first thing that I advise is to do is go out and buy yourself one of
these. Look closely, it is not just an ordinary tape measure!
Matthias works in metric; his plans and instructions are almost
entirely in metric, so you will want to have a metric tape measure at
minimum. I also have a combination square which reads in
metric, which is proving to be extremely useful.
I am not used to working off plans other than my own. I've been
designing my own projects pretty much since I began woodworking. So
working off of plans is already a stretch.
One thing unique about Matthias' plans is the inclusion of these 1:1
plans. I've watched several of his videos where he
demonstrates how he uses 1:1 plans in a lot of his projects. It
intrigues me, so with this project I went ahead and printed out the
1:1 plans and taped them together. (This took two tries, two sets of plans,
to get right. It is not quite as simple as he makes it look in his
And so I am trying out his method of taking some dimensions and cutting
instructions directly off of the plans.
You'll need to go shopping for some hardware. Some of the
requirements you might already have in your shop. Check through your
bolts and jig parts. The threaded rod, 2x10, and
other random t-nuts and so on, were easy to find at the local Big Box
lumber/hardware store. I also had some jig knobs/bits from Lee Valley
which I'd picked up years ago for various projects.
The metal bar for the miter slot is also
fairly easy to find at the local metal supermarket, though I haven't
yet picked it up.
The bearings are another matter. Home Depot did not carry them.
Princess Auto has some, but not the right size. I happen to have some
broken down Rollerblades which also has pretty decent bearings in the
wheels -- I plan to try to use one of those for the Idler assembly,
since I don't believe that the bearing size is critical there.
However, for the bearing that supports the threaded rod, size is
critical. You'll need to look up a bearing supplier in your
hometown. It was only about $3 each, so I grabbed two to have a
Here is the stock holding box glued and clamped.
Typically I build with hardwood.
Typically, Matthias uses a lot of softwood in his projects.
If you watch his videos you will quickly realize that he is extremely
frugal, and uses a lot of found or scrounged wood, as well as often
looking for more inexpensive ways to accomplish something rather than
simply buying the latest whatsit.
I do have extra hardwood on hand, and briefly considered just building
it all out of hardwood. But as this is my first time using one of his
plans, I decided to just go with his plans as much as possible and use
the same materials he does. As well, this is going to be a fairly big
jig, so I am also conscious of how much it is going to weigh!
I will make one comment on this step. The plans note that a
single 8ft 2x8 piece of construction lumber will provide enough wood
for the needed pieces. I would suggest instead buying the nicest 2x10
that you can find. Around here, the 2x10 lumber in the local big box
store is FAR nicer and clearer than the 2x8 lumber. Check the rings
on the end of the wood. With 2x8 lumber they can use smaller trees
than with the 2x10s, so by buying a 2x10 and cutting out your pieces
from the outside edges, you will get closer to quarter sawn, which will
be more stable, and farther from the pith of the tree.
Another thing: Do buy your 2x stock a few weeks ahead of time to
let it acclimatize to your shop. Construction lumber is not always
the most dry and stable. Even so I would also build the box the same
day that you cut and plane the pieces.
Here I am cutting out the slots for the corner splines in the stock
holding box. In the instructions/video he just uses a jury rig with a
cross cut sled. I can understand that, as it is only a few cuts.
However I found that procedure a bit unsteady. As well, building a
jig to hold this stable was only the work of about 10 minutes. You
can see that it is just 4 pieces of scrap plywood assembled with
NOTE: If you build a little jig like this, think
in advance of where you are going to cut. For the sides, I kept the
nails in the upper half of the boards. For the cradle portion, I
only put in two screws, and kept both of them at the extreme edges.
This leaves lots of room in middle for the saw blade. Note that for
this cut you are raising up the saw blade quite high, so you need a
lot of clearance around it.
Keep those nails away!
Early in the process, I realized that I needed the plans close at
hand. Fortunately I happened to have an old clunker laptop that I
could bring into the shop, which I did not care too much if it died
due to the dust or other shop hazards.
This way I now had the plan package close at hand, and I could flip
through the files, photos, instructions, as needed. Even more
importantly, I could play snippets of the instructional videos. I
found I would play roughly 1-3 minutes of video at a time, which would
give me pointers as to what would be the next step in the process.
For the thin piece of hardwood to glue to the front of the stock box, I
used some scrap maple hardwood flooring which I had obtained from a
neighbour some time ago. The baked on finish on this stuff is REALLY
hard. I learned the hard way to NOT try planing it off. Instead I
rip about a 16th inch off of the top with my bandsaw.
You can see the scrap on the left
-- the finish is really strong as you can see. Beside it is the
glue-up of two pieces of flooring
This is what happens when you cut a dado on the WRONG SIDE OF THE
LINE. ARGH. The tolerances on this project are very precise, so I
did not think I could just adjust the result, so I glued in a
carefully ripped pieced of maple and then proceeded. Thank goodness
for modern glues and long-grain joints! And thankfully I caught this
before I'd make the next cut, as that would have really set me back!
Here is the next cut, which was fairly complicated to set up. This
is the half-dovetail which is cut along the front of the stock-holding
box, for where the box rides along the front rail.
Got the t-nut mounting piece fabricated, as well as the dado in the
stock box where the threaded rod fits.
Gluing up some maple for the gear mount block. Working on this is way out of
sequence, but I discovered that I did not have a piece of 12mm Baltic
birch plywood that was large enough for the base. So, I'm kind of
stuck until I can get to the lumberyard to buy some more.
This gear block is a pretty beefy piece of wood. So you likely
will need to glue up a few chunks of hardwood, unless you happen to
have some particularly thick stock on hand. The left-hand frame
piece, where you mount the bearing, is another such piece. Three cm
thick hardwood (1-1/4") is also not the most common. I wish I'd taken
note of these pieces at the beginning, so I could get them all
prepared at once, rather than having to come to a stop right now as I
wait for the glue to dry.
Here is my first quibble with the plans -- and it's a minor one.
(These plans are awesome.) The 1:1 plans show the screw locations for
fastening the frame-front-rail to the base of the jig. The
instructions suggest that you just lay the plans over the base and tap
a scribe on each mark to transfer the location to the wood and then
drill the holes.
My quibble is that the screws for the front rail are all centered on
the front rail, which makes perfect sense. However at the left side
of the front rail, we have earlier cut the rail skinnier, so it is
only 3cm thick there. So those two screw locations are NOT
positioned over the center of the rail. On my build, my front rail
split when I screwed into it from the base. It was a small split and
I was able to force in glue and clamp it closed, and then reposition
the screw. I'm sure part of that is just the way the grain moved
through my piece of wood, but I do think that positioning the screws
so they were properly centered there on the left would have helped.
The front rail is just spruce -- very soft wood -- from a 2x10 from
the local building center. So in the original how-to video he did not
pre-drill these holes, and as I followed along neither did I. I
probably should have, as that may have helped also. I definitely did
pre-drill when I redid the hole in a new location!
I have written to Mattias about this, and it will be changed the
next time he updates his plans.
Oops. The instructions call for drilling a stepped hole in the left
side of the frame, where the bearing is inserted. However, I managed
to somehow drill the step on the WRONG side of the board. I
considered milling up a new board, but decided to just reverse this
board, as it was already milled to a perfect fit, and drill the
CORRECTLY POSITIONED stepped hole on the other end.
Also, I just happened to have a 7/8" plug cutter. (seriously, it's
the only one I have, from a project I built years ago.) So I drilled
out the stepped hole so it was 7/8" diameter the whole way through,
and then used the plug cutter to make myself a matching oak plug,
which I glued into the offending hole. A slim piece of oak was also
glued into the slot. I don't think a whole lot of strength is really
the issue there, but I liked the fact that I could (mostly) close up the
I then worked on the idler pulley assembly. Here I made use of a
bearing from a junked Rollerblade wheel. Since the inside/outside
diameters really are not crucial, this is a good place to substitute
for something free.
Unfortunately, on my first try, it is positioned too low. Note from
the photo how the bearing is riding against the softwood section of
the front rail. Not good. The bearing is already digging in.
Fortunately, it was a simple matter to reposition the hinge a few mm
higher on the side of the box.
Later on, since I had an extra rollerblade wheel bearing, I changed
the idler pulley assembly to ride on TWO bearings. This spreads the
load out over the wood also. (You can see this in a few photos way
near the end of this document.)
A view of the jig partially assembled. Next I'll be working on the
whole screw advance part of the jig.
Drilling out the axle hole from one of the two gears. This is
a mistake, by the way. After I drilled out the holes and then cut
out the gears I moved on in the instructions and realized that I was
supposed to mount a T-nut in the larger 16-tooth gear. This of course
requires a larger hole. The smaller 12-tooth gear requires the 3/8"
hole just to accommodate the threaded rod. (In my defense, I'll point
out that the drawing from the plans does not have this noted. But
really, it's my own fault. I was just following along with the
youtube video instructions, and this is noted in the written
instructions which I was NOT reading. I am now...)
The plans call for 39cm (15") of 3/8 threaded rod, and of course I
could not find that exact length in the store. It's easy enough to
cut with a hacksaw. After cutting, roll it along a grinding wheel at
a 45 degree angle, and you'll take off the burr and rough edges caused
by hacksawing, and you should have no trouble getting nut on or off.
(This is wonderfully illustrated by Ron
in one of his video shop tips.
If that link goes dead, simply google "Ron Walters cut threaded rod".)
What is going on?!? This is NOT going to fit in that space. There is
no way to tip in the threaded rod with the bearing and nuts into
place. I was perplexed. On the video, Matthias said it was tight,
but this is way more than tight! I double checked against the 1:1
plans and the dimensions of the gap are correct.
The problem is the same as on the gear noted above. Actually I
realized both problems about the same time. In the written
instructions, it is explained that he was using 9mm Baltic birch
plywood, which requires a 2mm wooden washer between the two gears. I
had been watching the video, as mentioned, and NOT reading the written
instructions, and I simply stuck in the washer. I was using 11mm
Baltic birch, and that extra thickness is enough.
The parts list notes that either thickness of plywood is fine. I think
that this is probably the only spot where you might need to make
allowances for the different thicknesses of plywood.
The video instructions are so good, that I had mostly been
building this by watching the Four step-by-step videos a little bit at
a time throughout the build. But These two situations drove home that
I also need to check the written instructions for more details that
are omitted or glossed over in the video.
Fortunately this was easily remedied by removing that wooden spacer.
And another view from the other side.
(Just a note for clarity -- in this picture I am just positioning the
rod + gears beside their mount point to verify that they fit. It is
not yet mounted into place.)
I'm about to insert the screws that clamp the bearing into place in
the bearing holder frame.
What I often do when fastening screws into hardwood is to dip the
tip of the screw into some paste wax. A bit of wax on the first
couple rows of threads just makes the screw go in quick and easy.
Of course I had also pre-drilled the holes (in
the foreground). But, this oak was quite hard, and I really
did not want any accidental splits. Cheap insurance.
Annnnnd another oops. This is supposed to be the gear mount block.
I'm not sure how I got the orientation mixed up
on this, but as you can see I ended up with the boards that make up
this block turned sideways. That is not terrible, but the other issue
was the holes that the bolts go into. You are supposed to drill these
holes a touch oversized (the gear mounts use a 5/16" bolt.) because
later you cut out the notch in the block and then it clamps down on
the bolt when you tighten the lock down bolt. I don't remember what
size drill bit I used but there was no way it would properly clamp
down on the bolt.
The truly silly thing here is that the blank that I cut the gear
mount block out of was large enough to provide two. But when
I cut it out I was not really thinking about saving the rest, and so I
cut the block out of the center of the blank, partly to avoid a small
knot, but mostly just because I didn't think I needed to save the rest
Oh well, time to reach for the re-cycled maple hardwood flooring
and quickly glue up another blank. Just for fun I slipped a piece of
scrap cherry in the middle. In time that will darken up (you can't
really tell right now) and give me a racing stripe in my block.
Drilling the mortise for the carriage bolt that clamps the block
And that is much better. Time to make another big gear!
I printed out the 48-tooth gear plan, stuck it to some Baltic Birch,
and started work. I forget why, but I got the idea that this was a
good size gear to start with.
Later on, I found a section of the build video where he explained a bit of
the gear ratios... The threaded rod is 16 tpi (threads per inch), so
each turn of the rod is a 16th of an inch in travel for the stock
holding box. Using a 48-tooth gear with the larger 16 tooth gear on
the shaft gives a 3-to-1 ratio, and with the 12 tooth gear a 4-to-1
ratio. (48 divided by 12 gives 4.)
so if you use a 48 tooth gear on the lower setting, so it engages
the 12 tooth gear on the shaft, then with each turn of the 48 tooth
gear, the 12 tooth gear spins 4 times, which yields four times 1/16th
of an inch, or one quarter inch of movement of the stock box. 1/4"
fingers in my box joints is what I'm aiming at to start, so that works
But back to the cutting of the gear. I first tried drilling a few
holes for the back of the gears, as you can see in the photo, but I
didn't like how it was working -- I mostly have twist drillbits. This
would work a lot better with a brad point bit! So I cut it all out on
the bandsaw. I tilted the table to the right for cutting one side of
the teeth, and then I wanted to tilt to the left for the other side.
My table does tilt a bit to the left, but I don't like to do that,
since it involves resetting the 90-degree stop that is on the saw. So
I built this little ramp for simulating the left-tilt. Works quite
In hindsight, I wish I had first taken the time to review his videos
on making gears. (Link
Here) I was worried that drilling the holes was affecting the
teeth. In that tutorial + video, he uses a drill for drilling out the
insides of all his gears. I now realize that the depth of the notch
between each tooth does not really matter much. What matters is the
spacing between each tooth. I had to do a fair bit of filing and
fiddling to get my gears to mesh nicely. I'm still not 100%
satisfied. If you build it, go check out that tutorial first!
On to the next problem...
I had the gears meshing well, I thought. But the mechanism was still
not working well. The gears did not seem to fit properly, and they
would jump out of the shaft gear's teeth all the time.
I was very puzzled for a time... Eventually I realized that this was
yet another problem with plywood thickness. Again, I used 11mm
plywood for my parts, and I think Matthias was using 9mm. The plans
say that either will work, but I don't think that is quite true.
Take a close look at the photo and you can see that the gears are not
fully mated together. The piece of plywood on the gear block is 11mm
thick, which I think is too thick. But I don't HAVE any 9mm plywood.
I tried to rip it skinnier (see
the chunk out of the corner?) My bandsaw blade just popped over and
would not rip it thinner. I was scratching my head for a solution.
I want this to be stable, so it had to be good quality BB plywood.
Fortunately, while I did not have any 9mm plywood, I did have some 19
or 21mm (3/4" equivalent) Baltic Birch. So I had a go at resawing
that down to 9mm in thickness, which actually worked perfectly.
After resawing, and then some sanding and drilling the proper mounting
holes, I now had a thinner mount under the gear, and the gears would
now full engage each other. Whew!
I was now nearly complete. The next step in the plans is to use some
3/4" x 3/8" bar stock to fit into the miter slot of the tablesaw and
fasten to the base of the jig. I don't have a tap-and-die set, and
could not find one at a price I was willing to pay. So I waffled on
this for a while, and eventually decided I would first give it a try
using just hardwood for the runners. I've had hardwood runners on my
Table saw cross-cut sleds for 10+ years with no worries so I thought
this was at least worth the attempt. I also discovered some well
seasoned tight grained white oak in my leftover pile. This is very
hard, and very dense, and I was able to cut out some strips that were
practically quarter-sawn with their grain arrangement. I'm hoping
that these will be stable enough to serve. I did go ahead and put two
of them on, one for each slot. The plans call for just one steel
The final step was to cut out a handle and fasten it to the front,
which brought me to the end of the build. Here are a few more photos
showing it from all sides.
Now the jig is built, the moment of truth is the actual use
the jig to cut some finger joints. But first, let us digress into a
bit of math.
On a woodworking forum I was writing about this jig and someone asked
about errors. Essentially, since I am just turning a crank (the big
gear), and there is nothing in the jig that makes the crank alwasy stop
in the same spot, can't errors creep in? If I don't always stop the
gear in exactly the same place, won't that affect the spacing?
The short answer is, of course, NO!
The more detailed explanation takes some basic math. Just a bit
further up in this web page, there is a section where I write about
cutting out a 48 tooth gear. As part of that I learned a bit of the
math for how this thing works, and wrote about that there. Here then,
is the second half of that discussion, which should explain why there
really is not any worry about error.
It goes a bit like this:
- I'm cutting 1/4" finger joints. I've got a Freud box joint blade set in
my saw, set to cut a nice square cut exactly 1/4" wide.
- I have a threaded rod that moves the stock box, which is 16tpi, (threads
per inch). So each full turn of the rod moves the box 1/16th of an inch.
- I have a 12 tooth gear (the smaller one) mounted on the rod, which I am
- I have a 48 tooth gear mounted in the gear block, which is meshing with
the 12 tooth gear.
- This big gear has a handle on it, which I use for turning the gear.
48/12 = 4. So each full turn of the 48 tooth gear turns the 12 tooth
gear 4 times.
- Therefore, each full turn of the 48 tooth gear turns the threaded rod 4
times. 4 x 1/16th = 1/4.
- Therefore, each full turn of the 48 tooth gear moves the stock one
- Therefore, for making 1/4" finger joints, I turn the 48 tooth gear twice
after each cut. That moves the stock 1/2". 1/4" for the bit just cut,
and 1/4" for the next finger.
So, the question remains. I am just eyeballing this as I turn the gear.
What if I'm off? What kind of error do I get?
First of all, the gear mounting block has a clamp in it. The 48-tooth
gear is removable. (So you can put in different sized gears for
different cuts.) So when I set up the jig to make my cut, I loosened the
clamp, lifted up the gear, and then moved it and set it back down such
that the handle on the gear was positioned right beside the secondary
gear. This gives me a nice visual reference for stopping the gear each
time I turn it.
But secondly, and more importantly, let's go back to math.
Suppose I do make a mistake. There are 48 teeth on this gear. Let's say
I make a turn and am sloppy and am off by one or two teeth when I stop
the gear, what happens? Remember, each full turn of the gear moves the
stock box 1/4". We're dealing with small measurements here, so I think
it is easier if we start talking about thousandths of an inch:
- 1/4" is is 0.25 inches, or 250 thousandths of an inch.
- 250 divided by 48 teeth is 5.2.
- Therefore, each tooth in that 48 tooth gear, in this setup, is
equivalent to moving the stock 5.2 thousandths of an inch.
- So if I'm off by two teeth, that is 10.4 thousandths of an inch.
One thousandths of an inch is .001"
- 10.4 thousandths is .0104" which is less than 1/64th of an inch (.0156")
--- It's actually about two-thirds of a 64th... Ummm, that is a bit
under 3/256th of an inch. (I'm the one doing the math, and I find 3/256th to be a silly fraction!)
So, in my example, if I am off by turning the gear two teeth, it is only
going to make a difference of less than a 64th of an inch. I don't think
that is really going to make much difference. (And I have a hard time
imagining being off by more than two teeth when turning the gear.)
PLEASE REMEMBER: This little bit of figuring is based on my
current setup. I am using a 48 tooth gear, meshed to the 12
tooth gear. A different setup is going to result in different
amounts of movement.
Now that the jig is built, it is time to test it.
I did not take pictures during my first cut, but I did during my second
test cut. I took several shots, which I hope does a good job of explaning
how to use the jig. As well, there are several videos on the woodgears
website that show the jig in use.
To start with, I want 1/4" finger joints, so I put in a Freud Box
Joint blade set. (That was the most expensive part of deciding to
build this jig!) Blades like this are not mandatory, you can make box
joints with a regular dado set, or with other blades. What you really
want is a blade that leaves a flat-topped cut, and my dado does not.
I layed a piece of stock down, and set the blade height to be just a
touch higher than the thickness of the stock. My goal is to have
fingers that are just a bit proud of the joint, which can then be
Next, stand up the two pieces for the test cut. If I was building a
box, I would have all four piece in at once. Snug up the pieces in
the corner of the stock box, and turn the crank until the pieces are
just touching the side of the blade.
One optional step here is to loosen the knob that is holding your gear
in the gear block, so that you can lift it up and turn it such that
the knob (or some other visual reference mark) is lined up with the
two drive gears on the threaded rod. This gives a nice visual
reference for lining up the gear as you turn it.
I am making 1/4" finger joints. So I need to turn the 48-tooth gear
one full turn to move the stock box 1/4". Then carefully slide over
the front piece of your stock, while leaving the back piece untouched.
And then clamp them securely in place.
Honestly, this was one of the most difficult bits to get right, as the
two pieces wanted to slide together. I would think it would become
easier with practise, and also if I was using heavier hardwood stock.
Turn on your saw and begin the cutting process. Push the jig with the stock
through the blade and back. Then turn the gear the required number of
turns and repeat until done. Again, I am making 1/4" finger joints,
so I need to move the stock double that -- 1/2" -- each time. So I
turn the large 48-tooth gear, which is meshed with the small 12-tooth
drive gear, two full revolutions.
And here is the result.
As an aside, I do not like the thin finger on the right edge of these
pieces. However, for utility shop projects, I probably would not
care. As well, these were just random test pieces that I grabbed from
the scrap pile. For ideal finger spacing, I would want to use stock
that is sized to be a multiple of my dado width, which is 1/4".
The joint slipped together perfectly. It was like magic. No sanding,
no chiseling, no fiddling. I just slipped it in, and tapped it
together. Note that this photo is actually of the very first
test joint that I cut with my jig.
And that is pretty much the end. I think I'm going to really enjoy
using this jig, and I can forsee a lot of use of it in future projects!