Re: Moulding Plane Sizes
Adam Cherubini, NJ
>Is there a guideline to how moulding planes are sized?
Check out C&W�s website for hollow and round sizing. Pretty sure the size given is the linear distance across an arc which is exactly 1/6 of a circle. For other molding planes, the number is often the width of the cut. (distance from fence to the inboard edge of the cut). So for an ovolo, it would be the edge of the board (fence side ) to the fillet. And that�s the horizontal dimension, not the vertical or depth dimension. As some planes are sprung (held at an angle in use) the width may not be immediately obvious. Also, old wooden planes made from quartersawn stock, shrink in width. So the number on the back probably won�t correspond to the actual width of cut anyway.
�what would be the best size to use for a given board thickness, �Is there any kind of rule/guidline?
There are all sorts of factors that govern that decision:
Structurally, the molding will weaken the edge, and that can be a problem. I often like shallow or small ovolos for frame and panel stuff (because of the groove). I chose the ovolo, which is convex, over a concave plane like a cove for this reason.
The shape of the plane esthetically reinforces what is happening structurally. Crown moldings are typically concave, base moldings are typically convex for this reason.
Shapes are chosen for practical reasons: Beads are used to hide gaps as are other quirked shapes. I like using a cyma reversa for dining table edges, because the convex outer most surface strengthens the edge and is nice to rest your arm on. Having the choice of several sizes, I pick the size that leaves golden section of edge un-molded. Where no plane would fit, I relieve the underside of the table until its right. Even though the table might be 6/4 thick, and I know how woodworkers like thick wood, I prefer that thinner more delicate, edge, so I�ll relieve it to 7/8�. It takes away some of the �Flintstones� look.
The size of crown or base molds is typically determined using the column orders. The only trick here is the ever-changing �h� in the equations. Seems to me, when it comes to moldings, �h� is rarely the height of the piece. Crown = 2/15*h Base = h/5
Otherwise, I don�t think there is any relationship between the number on the back and the stock thickness or anything else. That number is just there to help you order the right plane from the plane maker.
Adam