Upgrade your old jointer with a new spiral head
From power tools to computers, nothing irritates me more than saving up to buy a dream machine and then learning of a new technology breakthrough. Shortly after I bought my straight-knife 6" jointer, models started coming with spiral cutterheads that shear the stock for less tear-out on figured woods. Rather than invest in a new machine, I decided to try an aftermarket spiral cutterhead from Sunhill Machinery.
Unlike the spiral cutterheads that come on many 6" and 8" jointers these days (with dozens of square carbide cutters), the Sunhill spiral cutterhead uses flexible high-speed steel knives that conform to the spiral knife slots. This makes the cutterhead cut with an action more akin to the industrial cuttterhead that inspired spiral heads in consumer machines.
Before replacing my straight cutterhead—which has a fresh set of knives—I pulled out a piece of curly white oak and face-jointed it. Not surprisingly, the wild grain tore out badly. (That's why I typically machine this wood with a drum sander, removing a tedious 1/64" at a time).
Next, I swapped out my old cutterhead for the new, about a 20-minute job. I did notice that the pulley on the Sunhill spiral cutterhead didn't align perfectly with my jointer's drive pulley, but it didn't affect the performance. Once again, I face-jointed some curly white oak and, although not completely tear-out-free, the little bit of tear-out that occurred was shallow enough to remove with a few passes on my drum sander. That's a huge improvement.
Replacing the three strip knives takes only 20 minutes, and they self-index into a groove in the cutterhead. I pulled the knives out and then replaced them in a random fashion, and the cut was every bit as smooth as the one before.
The Sunhill spiral cutterhead has economy on its side, too: just $19 for a set of no-fuss disposable knives, and the cutterhead itself costs about half of what square-insert spiral cutterheads cost. Sunhill also sells replacement spiral cutterheads for 8" jointers, as well as 15" and 20" planers.
—tested by Jeff Mertz
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