For more information on the router plane, see our beginner site Common Woodworking.
I have a question. I noticed when you use your hand router, from what I’ve seen anyway, you’ve always used a cutter with a square cutting edge. Some router cutters come to a more pointed edge and I wondered why you don’t use those? And what are they used for? Wouldn’t using one with a pointed edge be a bit risky when finishing off like a housing dado because I figured the edge could cut into the walls of the joint. I don’t know why I was curious about this but I was. Felt like one of those if-it’s-not-broke-don’t-fix-it things to me, but I figured there must be at least one situation where maybe a pointed cutter was better.
At first glance this might look much more specialised than it really is and though it might be handy, it’s not necessarily essential.
The cutter is what was described as the smoothing cutter in the original Stanley leaflet accompanying the plane back in the 50s and 60s. Two things manage the cutter in the wood; one, the spear point bevels to each side of the centre of the cutter effectively bring the underside of the cutting edge to a level cut and so offset the relief angle of the underside of the cutter. This means that the two cutting edges are levelly present along the cutting edge in relation to the surface of the wood and so smooths the level evenly.
The angles presentation either side of the centre of the spearpoint also provide a sheer cut to the cutting edges and by manipulating the plane to the grain encountered the user can effectively gain optimal advantage in just about any grain.
The end result is a level and smooth cut, which effectively improves on the cut provided by the square edged cutters and is ideal in some situations such as inlays for instance.
Generally 95% of work comes from the square edged cutters satisfactorily and so it’s not necessary to install a spear point.
Visually considering the appearance of the cutter it does look as though in actual use the spear point might dig in to the walls or surface being refined but that is not the way at all.
The drawings below show the diamond point and the angled presentation of the cutter to the housing dado or work surface.