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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