TECHNICAL Mortise & tenon joints
40 The Woodworker & Good Woodworking October 2019 http://www.getwoodworking.com
FURTHER INFORMATION
Trend DBB mortise & tenon jig –
http://www.trend-uk.com
PantoRouter –
http://www.woodworkersworkshop.co.uk
Woodworking Guild of America – http://www.wwgoa.
com/article/12-tips-for-using-a-router-safely
Tuffsaws – http://www.tuffsaws.co.uk19 Set the sub-fence to the length of the tenon
and cut the shoulders – again, test on scrap to
ensure accuracy
22 Cut the haunch to length in the same way
as the shoulders20 The space created by the sub-fence allows the
waste to fall away safely and not jam the blade21 Cutting a haunch follows essentially the same 23 The completed haunched tenon
principles. Start by marking out one tenon and
cutting to the mark
For some reason, manufacturers are notorious
for supplying beautifully-engineered bandsaws
with bargain-basement blades – so if your
bandsaw won’t cut straight, firstly change the
blade. That won’t be wasted in any case, and it
might well save a whole lot of hassle. Tuffsaws
are a specialist supplier of excellent blades and
their website is a treasure trove of reliable advice
(see ‘further information’ sidebar at the end of this
article). If need be, don’t be afraid to call them.
Straights & curves don’t mix
A common reason for blades not cutting straight
is if they’ve previously been used to cut curves.
That process very quickly imposes uneven wear
on the teeth, causing it to pull off-line. So keep
a blade that’s reserved for straight cuts only and
NEVER used for curves. If after all that, the cut
still isn’t parallel, then it’s time to think about
adjusting the fence, as per your machine’s manual.
Perpendicularity
The next thing to ensure is that the blade is
running vertically at right angles to the table.
This, especially on a new hobby machine, might
need some adjustment. The angle can be tested
with a small engineer’s square (OK if you know a
helpful small engineer...) Alternatively, take a nice,
square piece of scrap wood and make a short cut
into the end (photo 7). Then flip the timber end-
over-end, and offer up the cut end to the back of
the blade (photo 8). If the blade is perpendicular,
then the cut end will slide smoothly over the back
edge of the blade. If it doesn’t, then check the
manual and adjust.
So let’s cut a tenon
With the blade cutting perpendicular to the
table and parallel to the fence, the way is open
to cut some nice, precise tenons. Doing this by
hand would involve marking every cut on every
piece of timber individually – but the bandsaw
eliminates almost all of that. Instead, you can just
take a little time to set up the machine for each
stage before cutting all the pieces on that setting,
quickly and accurately. For that, you’ll need a little
spare timber for trial and error work, and it needs
to be the same width and thickness as the timber
being used in the job itself. The simplest way to
achieve this is to prepare a little more timber than
actually needed for the project. It’s important to
ensure that all four sides and the ends are nice
and square because in this work they’ll all have
to serve as datum surfaces, referencing off either
the fence or the cutting table. (Just continue
reading and the fog will clear!).Safety first!
The bandsaw is a safer – or, rather, less
dangerous – machine than many others, but it’s
still capable of doing soft human flesh a mischief.
Don’t skimp on reading the safety instructions
that come with the machine. A couple of points
I should particularly highlight here: firstly, only
have the machine running when you have to- and never with the doors open (assuming the
machine will do that, which it really should not).
Secondly, in the photos, I’ve got the guard raised
higher than is advisable in normal practice. I tried
to set it low over the timber, (photo 9) but it just
made photography impossible so I raised it for
the purpose of this article. However, in general
usage, the less blade is exposed the better –
so, as a matter of good practice, get the top
guard well down over the timber.
The cutting process in a nutshell is to set the
machine up for the tenon cheeks and cut those
on all the pieces (photos 10-15); then set up for
the shoulder cuts and cut all of those (photos
16-20), and finally set up and cut any haunches
that are necessary (photos 21-23).
It’s important that each stage is completed
on all pieces before resetting the machine for
the next – e.g. ensure that all the tenon cheeks
have been cut before resetting for the shoulders
(the voice of Bitter Experience...)
It’s worth emphasising the importance of the
short sub-fence for cross-cutting (photo 18). The
temptation is to use the rip fence as an end-stop
and butt the end of the timber against it, but
don’t. Kick-back isn’t an issue on the bandsaw as
it is on a table saw, but it is possible for an offcut
to twist in the gap between fence and blade, and
jam the machine. The short sub-fence makes
space alongside the blade for the offcut to fall
safely away without jamming (photo 20).
The final task is to cut any haunches that
are required, using the same basic approach
as for the cheeks and shoulders (photos 21-22)
and all the joints are cut – safely, precisely and
much, much more quickly than would have been
possible, marking and cutting each joint by hand.
Before ending, I just want to reiterate the
warning about the guard – mine is raised in
the photos for ease of photography but would
not normally be so. It only takes a momentary
distraction or a touch of complacency for an
accident to happen. So please – in this instance
at least – ‘do as I say and not as you’ve seen
me do’! And then, join me next month, as I cut
some tenons for real and make a handy little
crafting table.