: I work a lot with 3 mm ply and it is difficult to get a really good scarf
: joint as the ply tends to curl slightly at the edge, and small errors are
: more important in thin material. I now use a belt sander, with a steel bar
: under the edge of the ply and another behind the cut and parallel to it.
: The belt sander stops cutting when the belt contacts the bars and leaves a
: perfectly flat cut with a feather edge. The pressure of the tool keeps the
: ply flat. I am going to try rollers.

I cut all my scarfs with a belt sander. Trying to do it with a block plane is very difficult. I put a scrap piece of wood as the bottom layer. The bottom piece seems to lose its sharp edge easy because there is not a lot of wood there when sanding. So add a scrap piece on the bottom and you will get great scarfs. I typically do only two scarfs at a time so they are perfectly matched.

Kyle