Analyzing our data pools, it became apparent that handmade furniture doesn’t remain within its average tolerances the way machine-made furniture does within its level of precision. This 0.01" mechanized range is an absolute boundary, and for the most part there are simply no outliers beyond it. Straight and parallel are predictably regulated by machines, and are in fact necessary for the industrial manufacturing process. CNC machines, for example, rely on unmovable benchmarks that must be established to function properly. Throw a piece of tapered, warped, rough-cut lumber on the worktable, and you’re asking for trouble. However, the measurements we took from our pre-industrial examples were rife with outliers – areas of noticeable, often radical divergence from general tolerances.
It is usually considered bad form or even data massaging to remove outliers from an analysis, especially when one is specifically focusing on variations across a test pool. We’ve all seen funky pieces of old furniture where, for example, a board on a side might vary in thickness from 1/2" to 7/8" over just a small span, as we saw on a chest that was one of our test pieces. Because such a large discrepancy is so clearly visible by eye, one must conclude that this was an acceptable deviation by the maker. Pre-industrial craftsmanship is rife with such pragmatism in the name of efficiency. Parts turned on a lathe from riven stock, for example, often retain riving marks even on the finished chair or table, presumably because the blanks split out of the log were just barely larger than their intended final turned dimensions. These riving marks are usually turned downward or inward during final assembly, minimizing their visibility. In making measurements with digital calipers, these areas show up as radically divergent.
Another explanation for outliers is the connection of the craftsman to the material. Machines can mill technically perfect dovetails through any knotty rebellion (although sometimes this may destroy the piece being milled), while a craftsman cutting dovetails by hand will selectively move or adjust cuts to work with or around difficult areas. One drawer we measured has a series of tiny, precise dovetails holding the drawer back in place, but in one area containing a knot, the pin is cut larger to accommodate potential weakness in this resinous grain. Going by measurement alone, this is an outlier, but does not necessarily denote any imprecise workmanship that could skew the assessment of this piece.
–Michael Updegraff, excerpt from “In Pursuit of the Handmade Aesthetic,” in Issue Four