What are helical spiral cutterheads and why are woodworkers becoming confused?


One of the questions we encounter nearly everyday is ‘What's the difference between the spiral cutterhead on this $900 thicknesser and this $1,600 thicknesser?'

It's usually followed by 'How much longer do spiral cutterheads actually last than regular straight edge?’ They're the kind of repetitive questions we don’t mind answering, because it reminds us a little of when router bits evolved from high-speed steel to carbide tipped: honestly, the look on a few of our customer’s faces when we let them in on the worst kept secret in woodworking is pretty rewarding.

But after doing some research it turns out there’s some misleading language out there, and we think it’s time someone clarified the situation once and for all…

The long and short of spiral cutterheads, helical paths and some dodgy marketing spin

In case you’re wondering what we’re talking about, helical path spiral cutterheads are the new in-vogue addition to any thicknesser or jointer that’s worth the timber it planes. 

The helical-path spiral head uses 27mm-wide knives - these are almost double the standard 14-15mm knives on other segmented cutterheads, creating a finish twice as smooth, twice as quickly.

The extra-width means each tip passes over more of the material, leaving a smoother finish. It’s a smarter, more efficient design that not only improves cuts and machine-lifespan, but can save you a ton in replacement blades. But we’ll get to that later.

That tentacle design on helical path spiral cutterheads

Helical-path spiral cutterheads are designed with a true shear cut, which means the knives are arranged in a helical spiral pattern and set at relative angles.

Instead of punching the material at 90°, one knife shears smoothly across the timber, before the next knife engages at the exact same angle. It’s far less work for your machine’s motor, which means true shear-cut helical spiral heads require less horsepower.

They also make smaller chips and operate with far less noise than other types of cutterheads. Unlike conventional single straight knifes, you don’t even need to replace the knife if it becomes damaged or dull. Instead, if one knife edge is damaged or needs sharpening, simply turn it to another edge in seconds.

You will only need to replace the inserts when four edges are dull. Compare this to your speed-steel knives and you’ll think your machine has discovered the fountain of youth.

So why is there confusion around spiral cutterheads and the helical path?

One of the problems our industry faces at the moment - and one of the reasons we get a lot of questions - is the variance of confusing terms that apply to cheaper machines.

You cannot find a machine under $1,000 that has helical-path spiral cutterheads - sure, they might have spiral cutterheads - but without the helical path engineering, they don’t have any of the spiral cutterhead advantages. So you can see why they still use the term ‘Spiral Head’.

Due to the complicated nature of designing each blade at a relative angle to each other, there is significantly higher cost in engineering and precision machining a helical pattern.

So don’t get confused by the misleading language here – check that the machine’s knives cut with a helical spiral pattern, that they have the extra-width and they’re not just imposters.


How long do spiral cutterheads last?

When router bits transformed from high-speed steel to tungsten tipped it increased the lifespan of your average bit by about 8-10 times.

Now you probably wouldn’t dream of buying a router-bit that wasn’t tungsten, right?

Well it’s about to be the same with helical-path spiral cutterheads. You only have to rotate your spiral-head knives once for every 8-10 blade changes on straight high-speed steel blades.

That’s 8-10 times more efficient straight away. But the kicker is you can then rotate each knife four times before replacing it. This means the knives will last up to 40 times longer than straight blade knives. Yep, you read correctly. All cutterheads come standard with solid carbide knives and replacement packets of 10 are available separately.

Then, when you eventually do need to replace them, they screw in evenly in a matter of seconds – no more jigs to align them with each other.

Helical-path cutterheads have been around long enough to know that there’s no downside to any aspect of the maintenance or operation, you’ll begin saving money the minute you install them in your machine. The only drawback is that initial investment is larger than a simple carbide-tipper router bit.

The sharpest jointer knives in the drawer

Woodworkers buy these type of cutterheads for the quality of the cut and the removal of stress on their machine alone, but approaching the argument on a purely cost-for-cost basis, they’re an expensive proposition in one-hit.

That’s because these cutterheads are basically offering the opportunity to confine a series of prolonged and hidden costs into one direct payment.

So ask yourself a few questions:

  • How true are your machine’s knives, and how much could a more accurate and efficient machine save you?
  • How many of you have bought a second set of straight blades trying to avoid sharpening downtime?
  • How much time and money is the overall resharpening process costing you?
  • How inconvenient is the process of replacing the knives, reinstalling and then maintaining the cutterhead so it accurately manages the cutting edges?
  • Finally, how much longer could your entire machine last if you were taking almost half the stress out of its operation?

Take some time to think it over and if you’re still uncertain about any step of the process get in contact. Like any innovation, there’s a start-up cost, but boy is it smooth-sailing when you finally leave the harbour…