A tablesaw tenoning jig is an essential tool for most
woodworkers. But commercial units cost $100
and up, and shop-made jigs that I’ve tried, all riding
on the fence somehow, were unstable and
hard to adjust. So I devised this jig, which features
the safety and stability of a crosscut sled, combined
with a micro-adjust tenoning carriage. With it, you
can safely and accurately cut tenons, half-lap and
bridle joints. Best of all, it’s cheap and easy to
make; all you need are a couple pieces of scrap
hardwood plywood and $10 worth of common
hardware store items.
How it works
The jig has two parts: a fairly traditional
crosscut sled that rides in the miter gauge
slots; and a carriage, which is held by a
threaded rod (Fig. A). When you crank
the threaded rod, the carriage moves
1/16 in. for each full turn. A locking
clamp holds the carriage in position
when you’ve got it set just right.
To make tenons, clamp each workpiece
to the carriage and cut one cheek
(Photo 2). Readjust the jig and cut the second cheek on all pieces. Now, here’s
a great feature of this jig: To cut the
shoulders, you use the crosscut sled part
of the jig, and the carriage becomes a
micro-adjustable stop, making this second
part of the tenoning operation quick
and accurate (Photo 3).
This jig is also designed for safety.
Unlike many tenoning jigs, your hands
are far from the saw blade at all times. A
wooden blade guard houses the blade
after it makes the cut, and it’s easy to rig
up a stop that prevents the jig from
going too far forward (Photo 1).
The basic construction of the jig is
straightforward, because it’s essentially
made of plywood boxes. When you cut
the parts, make sure they are dead
square, because the accuracy of the jig depends on it. The rabbets help keep the
pieces square during glue-up. You may
find it easier to make the cutouts for the
handle before you cut out the parts, just
because you’ll have more material to hold
on to. I drill two holes and then use a jigsaw
to connect them—you could use a
scrollsaw or router as well. Make the
clamp hole in the carriage with a hole saw,
then save the circular waste piece to use
under the lock knob.
I made the locking clamp and the
crank from wood, but commercial
threaded knobs work, too.
The adjustment mechanism
The heart of this jig is the micro-adjust
mechanism, which consists of two parts:
an aluminum bar with a slot in it; and
the threaded rod, with a groove filed in
it. The groove fits in the slot, to capture
the rod. To cut the slot, drill a 1/4-in.
hole in the aluminum bar (available at
hardware stores) and use a hacksaw to
cut the sides of the slot. To cut the groove
in the threaded rod, chuck the rod in an
electric drill or drill press and hold a file
to it (Photo 4). Check that the slotted bar
fits neatly on the threaded rod. If the
groove is too wide, put a pair of nuts on the rod and tighten them
against the bar.
To make the crank handle I
used a piece of 1/2-in. dowel.
You can also use a piece of
scrap tubing or pipe. There’s a
trick to drilling a hole through the middle:
Clamp a piece of scrap to your drill
press table and drill a 1/2-in. hole in it.
Put the dowel in the hole, and you can
drill a 1/4-in. hole neatly through the
Assembling the sled
I made my sled runners from ultra-highmolecular-
weight (UHMW) plastic (see
Materials List, below), which is slippery
and makes the jig slide easily. Maple or
another dense hardwood would also
The runners must be attached exactly
perpendicular to the fence at the back of
the jig. Here’s how to do it: First, make
sure that your tablesaw blade and rip
fence are exactly parallel to your miter
slots. Set the runners in the slots and
place the sled on top of them. Lock
your rip fence next to the sled, and use
a large, accurate square (a drafting triangle
is good) to set the sled’s fence
perpendicular to the rip fence. Drive a
couple of brads through the sled into the
runners to hold them, then screw them
Make test cuts to be sure the sled is
giving you square cuts, then attach the
tenoning carriage and you’re ready to
Fig. A: Exploded View
Click any image to view a larger version.
1. The jig consists of a crosscut sled that
rides on runners, with a laterally
adjustable carriage that holds the workpiece.
A stop prevents the jig from sliding
too far forward.
2. Cut tenon cheeks with this jig by clamping the
workpiece to the micro-adjustable carriage, which
is attached to a crosscut sled.
3. Cut tenon shoulders using the crosscut sled part of
the jig.The micro-adjustable
carriage is used as a stop to
control the cut location.
4. A grooved threaded rod is at the heart of the
groove is made with a file while
the rod is turned slowly in a drill
or drill press.Two nuts tightened
against each other make a stop
to help control the file.