The Veritas Combination Plane
More on dados or housing joints
A
question came up about the width of a dado off a dado plane … that
the width of the dado cannot be calculated from the blade, per se,
since the nicker is an additive factor.
Positioning the
nickers is at the heart of setting up a dado plane, be it of the
combination plane style, where there are individual nickers, and
placed at either side of the plane body. A combination plane extends
the width of the body using two skates. There is a second type of
nicker system, which is a single nicker divided into two cutting
sides. This is the version used by many vintage woodies and, more
recently, HNT Gordon.
Close
up of the nicker …
With
the Veritas, there is a nicker on the outside of each skate
...
This
is adjustable, using a set screw, which pushes the nicker/blade away
from the body.
My preference (which runs against the
recommendation of Veritas) is to remove the set screws (because they
fall out and get lost otherwise) and set the nicker for minimal (more
on this in a moment) projection from the skates. As mentioned before,
I rounded the tips of the nickers (they came pointed). There were two
reasons for this. Firstly, the original tips of my pre-production
plane were fragile and broke off. I hardened them. Secondly, the
rounded edge seems to me to slice more easily than a pointy tip, and
the plane cane be drawn back of the work piece as well as pushed
through it. In other words, it is less directional.
The
depth of cut is not really a number. Numbers are starting points. Say
1/16". We really want the nicker to be set a smidgeon more than
the depth of cut, as it needs to slice the cross grain ahead of
the blade. Too deep and the nickers will just make the plane harder
to push.
Now
warren made an important point at the start of this thread when he
wrote that, because the nickers must lie outside the side of the
blade, they cannot leave a dado the width of the blade. I agree with
this, and it becomes the main topic here.
If using power tool
methods, it is possible to prepare boards (to fit) and the dados in
an interchangeable order, since they can be made to the same width.
For example, a 1/2" power router bit creates a 1/2" dado,
and one can thickness 1/2" thick boards quite separately. On the
other hand, if using hand tools, it is relevant to create the dado
first and the board thickness second - based on the width of the
dado.
The question is "how close to 1/2" can
we create a dado?". In other words, assuming a 1/2" wide
dado blade (straight or skewed), what is the minimal amount of dado
projection we can get away with before the side walls begin to
spelch?
So I set up a simple examination (this took far less
time than the write up!). Veritas and HNT Gordon planes and a
small piece of Radiata Pine scrap ...
The
Veritas blade is exactly 1/2" (as one might expect) ..
Now
I have stated before that I set up the nickers flush with the sides
of the skate (and then adjust the skates outside the blade). This is
not quite accurate. Indeed I set them up this way ...
Why
I say that this is not quite accurate is that my nickers have been
used with the set screw, and this has deformed them very, very
slightly. So now, when I try and set them flat against the side of
the skate, they do not sit flush, and project very, very slightly. I
cannot measure the amount of projection, only feel it with a finger
tip. This has a bearing on the set up and the results. More in a
short while.
Here is a tool needed for planing dados - a
straight edge. Traditionally, one would simply nail a wooden fence to
the work piece. The nail holes would be either filled or ignored. The
Veritas requires the fence to be a 1/4" high. So I have a
straight edge with non-slip and a square reference at one edge
...
If
the work piece is held firmly, it becomes a simple matter to clamp
down the straight edge ...
I
then pull the plane back against the fence, but very lightly. All I
want is a positioning of the outside nicker ...
Nickers
are not always the cleanest cutters - not sharp enough - for leaving
a pristine side wall. And so I prefer to knife them in ...
Now
go ahead and plane the dado, beginning at the far end. The depth stop
will keep it level (note that I have not relieved the end of the dado
here, as I generally would to prevent spelching. This example is
about the nicker, not the finish at the end of the dado. I am not
even using the depth stop).
How
wide is this?
That
is 0.55mm/0.02" wider than the blade. mmmm .... not that great a
result as far as I am concerned. I am sure it is possible to do
better.
The HNT Gordon dado plane is my reference here. It is
set up in a similar way, but stock standard. The blade was previously
measured also as exactly 1/2" (12.71mm on this occasion). It has
a skewed blade, but that only affect the cleanness of cut (the skewed
blade leaves a cleaner finish). The nickers protrude from the body of
the plane, but again I can only feel this with fingertips as it is
not obvious.
A clean slate ...
Planed
...
Measured
...
That
is a better result than the Veritas. So, let's try the Veritas again,
with the skates set up a tad closer together ...
That
is a tighter fit for a 1/2" thick board, and visually it looks
good in that there is no spelching. As I look at the photo now, I can
see compression on the right sidewall. It is not present on the left
sidewall. Is that from knifing the line, or from the nicker?
In
conclusion, as one moves the nicker closer to the blade, the leeway
for error is lowered. One question is "Is it worth it?". I
guess the answer is that one needs to recognise that hand tool work
is best done in a specific order. Power tool thinking needs to be set
aside here. It is evident that one can get pretty damn close to the
width of the blade - the amounts exceeded here are unlikely to be
registered visually - and that the amount of leeway can be pretty
damn small.
Regards from Perth
Derek
March 2019