Spiral Heads and Reading the Grain

Spiral insert knives are great for eliminating tearout, but just learning to read the grain can take you a long way. October 15, 2010

Question
I have an 8" Jet jointer (a run of the mill offshore machine). Is it worth putting in the money for an aftermarket spiral cutter head?

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
Why are you interested in the spiral head?

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From contributor F:
I have been jointing the edges and faces of solid hardwood for decades using straight high speed steel knives only. I check by eye for the best feed direction with regards to the grain and take a pass. If I get tearout, I flip the board 180 degrees and take a second pass. I now know the best feed direction for that board and keep track of it with a simple mark on the endgrain for all further milling operations. After the first pass on a board, I also know how fast I can joint that particular edge or face and still avoid tearout.

As far as I can remember, the only specie I have ever had and serious trouble jointing or planing was birdseye maple. Not trying to dissuade you from spiral, but rather point out that regular cutter heads work fine if an operator is old school enough to consider the grain direction of the boards he is machining.

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From contributor R:
We recently added a spiral head to our 16" Invicta jointer. Huge difference! I still read the grain of the boards and feed them properly, but mostly so that I know which way to feed them into the planer.

The spiral really works well on figured woods, and is far easier to feed, as well as quieter. One big advantage is that if someone misses a staple, it is quick and easy to rotate a couple of the inserts rather than having to regrind the full knives.

That said, I would question adding on to an 8" jointer. Is the jointer worth the cost of the spiral and the labor to swap it over? 8" is pretty limited for most professional shops, and I'm guessing you may be much happier buying a larger jointer with the spiral already mounted. In the current economy, there is quite a lot of good used equipment on the market, and the prices are great.