Many woodworkers have a molding plane or two in their shop. They were handed down from earlier generations or picked up at an antique sale or store. And if you’re lucky, the plane wasn’t beat to pieces and the blade was never sharpened by someone who lacked the necessary knowledge.
In my opinion about 25 percent of the antique molding planes still around have damage to the either the mouth, which is often erroneously enlarged in an attempt to reduce or eliminate clogs, or to the wedge and its shaped finial. If the finial is not cracked off due to being whacked to try to loosen the wedge, the wedge itself is mistakenly thinned for a better fit.
One of the most-often confusing attributes about molding planes to an inexperienced woodworker – and a huge problem when it comes to properly sharpening these tools – is that the profile of the iron is not a match to the profile of the bottom of the plane. Because the blades are laid over at an angle, the shape of the cutting edge has to be adjusted to provide the wanted design. The best way to see this is to examine a beading plane – the shape of the blade’s cutting edge has the bead elongated. It’s not a straight bead.
After you understand how to obtain the proper profile of the blade, you’ll need a way to sharpen it. You can sharpen molding-plane blades by hand; it was done for hundreds of years. But today most of us use a grinding wheel of some kind. (Fig. 1) There are a few things to know as you sharpen plane blades on a wheel. The most important is to take it slow. Nothing about the process I share is quick. If you work fast, you could easily turn your plane or blade into rubbish.