Spiral Cutterheads for the Jointer: Worth the Upgrade Price?

By Paul Mayer

Photos by author unless otherwise credited

Posted September 6, 2011

Photo courtesy of Grizzly Industrial

Nope, that’s certainly not your grandpa’s jointer cutterhead.  It’s called a spiral cutterhead.   It is a newer design that uses the concept of insert tooling rather than traditional straight knives installed in the cutterhead.  Small square carbide cutters are placed in close proximity to one another along a machined spiral pattern in a steel head.   This same technology is available for other tools as well, such as planers, shapers, and moulders, but since the purchasing criteria may be different for these applications, I will focus on the use of spiral cutterheads in jointers for the purposes of this article.

Spriral cutterheads are considered an upgrade for a jointer, and generally carry a premium of $300 to $1,700 depending upon the size of your cutterhead.  Many manufacturers now offer this as an option that can be factory installed in their jointers when initially purchased, and they are also available as a retrofit that you can install yourself.  In my opinion they are superior to traditional knife-based cutterheads in nearly every respect, and the question of whether it makes sense for an individual to purchase one comes down to whether the incremental cost is worth it to that particular woodworker, given their specific requirements.

To evaluate whether or not it is worth the money to you, here are some of the key benefits to consider:

Edge longevity.  Spriral cutterheads utilize carbide steel inserts, while most knife-based cutterheads incorporate knives made of high speed steel.  Carbide normally holds an edge for at least three times as long as high speed steel, and much longer than that in many cases.  This translates to less time between swapping out cutters.  Plus, the insert cutters for spiral cutterheads normally have four cutting edges on each one, so if one gets dull it can simply be rotated, and the jointer is immediately back in production.  Depending upon the cost of sharpening and replacing knives in your area, it is unlikely that this longevity advantage alone will ever single handedly justify the cost of the spiral cutter upgrade, but it is a factor that can offset some of the price differential, so it is worth consideration.    

Super easy cutter changes.  Depending upon the design of a given cutterhead, swapping out knives can be a cumbersome, time consuming process.  With spiral cutterheads, the process could not be much simpler.  Remove one screw, rotate the cutter 90 degrees to a fresh edge, tighten it down, and resume jointing.  

Setting knives can be frustrating.  This can take a while, and can lead to inconsistent results in getting the knives consistently set to the perfect height.  Of all the factors to consider with spiral cutterheads, this one appeals to me the most, as I am not a fan of swapping knives in a jointer.

Minimal disruption from knicks in knives.  With high speed steel knives, if you knick one of your blades, you either have to remove the blades and sharpen the set, or try to slide the knives so that the knicked portions of the blade no longer align.  This presents either a cost factor, hassle, or both.  With spiral cutterheads, you simply rotate as described above and you are back in business. Plus, since the inserts are made of carbide, the likelihood of getting knicks in the cutters goes way down in the first place.

 
Quieter. The spiral cutterheads operate much more quietly than knife-based cutterheads.  Although I don’t own a sound level meter so I can’t quantify this, the difference to my ears is pretty dramatic.

Joint MDF or plywood.  If you ever have a requirement to joint man-made materials such as MDF or plywood, you can do this with confidence using a carbide insert cutterhead, while this is not recommended with traditional knives (although I will admit that I have jointed plywood with knives a time or two).

Easier dust collection.  A minor benefit is that the smaller cutters on spiral cutterheads break the material into smaller pieces, so slightly less suction is required to extract the waste back to a central system.

Better surface on figured wood. This is the point that seems to get all of the attention around the internet.  From my standpoint, I have used a jointer with HSS knives for over a decade and have had adequate results when face jointing figured stock, provided my knives are sharp and set properly, the jointer is tuned, and I take light cuts with a slow feed rate.  I don’t rely on a jointer for a finish-ready surface, so even with a spiral cutterhead, I will continue to scrape or sand to a final surface.  Having said that, the results that I have seen so far using a spiral cutterhead on figured wood have been nothing short of spectacular.  I have face-jointed birdseye maple, curly birch, quilted maple and quartersawn white oak, all with great results.  

Helical cutter-head with cutters skewed at an angle for sheer cut

Spiral cutter-head with cutters perpendicular to feed direction

Helical vs. Spiral.  When looking into spiral cutterheads, you will hear the terms “spiral” and “helical” used nearly interchangeably, but there is a slight difference between these two designs.  Both designs feature a machined steel head with small square cutters placed along the surface in a spiral pattern.  The primary difference lies in the orientation of each cutter.  Spiral cutterheads position each blade so that the active cutting edge is perpendicular to the jointer’s feed direction.  This would be a similar cutting action to a hand plane taking a cut straight into the grain of a piece of wood.  Helix cutterheads on the other hand operate more like a sheer or skew cut taken with a hand plane, as the cutters are positioned at an angle to the feed rate.  In theory this shearing action should provide a superior finish, just as it does with a sheer cut on a hand plane.  In practice however, when applying a slow feed rate and a shallow cut the surfaces produced on figured stock by each style cutterhead are nearly perfect to the naked eye, so it is difficult to substantiate a claim that one is better than the other without employing some level of magnification.  And at that point it becomes a science project rather than a meaningful measure of woodworking precision or productivity, which causes me to lose interest.
 

Decisions, Decisions.
Is a spiral cutterhead right for you?  If you are thinking about this upgrade, the following simple table might help you weigh out the trade-offs.

Conclusions
I like the concept behind spiral and helical cutterheads, and I took the plunge and ordered one with my recent jointer purchase.  As a hobbyist, I will admit that I consider this a bit of a luxurious indulgence.  I don’t use a jointer enough to justify the expense based upon any cost savings I will incur down the road.  But the surface quality, quieter operation, ease of blade change, etc., make it an attractive upgrade for any woodworker who can afford one without cutting into grocery money.  

For professional woodworkers who use their jointer a lot, I believe that this upgrade is a no-brainer.  Minimized downtime due to blade swaps, less sanding time on face jointed surfaces and fewer sharpening expenses all add up to real savings and a competitive advantage due to better productivity.  

What do you think?  Are you using a spiral cutterhead in your jointer?  If so, let us know why you bought it and what you think of it in the comments section below.  Questions?  Please feel free to post those in the discussion forum so we can continue to add to the knowledge base that is growing there.