There I was, just flipping through the several pages of planes in The Book of Plates that LAP produced - as I do just about every day, it seems. (I tell ya, this book is worth its weight in gold to me.) So, this particular day, I was meticulously studying the plane irons because I am delving further into making planes that are based on Roubo's drawings. I'll actually be contributing an article to Popular Woodworking in the near future on this subject. I promise that all of you aspiring planemakers out there will love it. It doesn't require any specialized tools and they are very simple to make.
|Roubo style plane based on the Book of Plates|
Anyway, I have been trying to decide how I wanted to go about making the irons. I just assumed that his irons were tapered from thick at the cutting edge to thinner at the opposite end. Then I just happened to flip to some pages showing some of his earlier drawings and BAM! there it was - a side view of the irons clearly showing both the bench plane and the side escapement plane with parallel thickness irons! No taper!
I know what you are thinking, "He just didn't draw the subtle taper of the irons." This is possible, but he clearly knew how to draw a tapered iron because the plow plane irons on plate 16 are clearly tapered. However, the irons shown on plate 13 are not tapered even the slightest.
|Roubo - Plate 13|
This sort of rocked everything that I assumed about antique irons. Most of those I know who think on this subject believe that the irons were tapered to save metal. So what is going on here? Could it be that the tapered irons of the British and American planes were made that way because it, in fact, added functional value? I believe this is the case. I think this actually gives reason to believe that the added functional value of tapered irons wasn't just an unintended benefit of a frugal planemaker. Maybe it was an accidental discovery, but continuation of the practice was surely intentional. After all, if the reason was only to save metal, then why would the planes Roubo knew of have even-thickness irons from toe to heel? Wouldn't they be interested in saving iron too? Wasn't it just as expensive for them at the time? And, wouldn't it be more difficult for a blacksmith to make an even-thickness iron? Lots of unanswered questions here, but I wanted to share my findings with you all. I personally hate to speculate too much, but it is interesting, nonetheless.
One thing is answered, though: I have wondered why there was a sneck on his irons. This explains it! I am still sold on tapered irons, but this gives some food for thought.