Get the Skinny on Spiral Cutterheads

With many manufacturers adding the option of spiral cutterheads to their
jointers and planers – if you toss out the standard three-knife
cutterhead and pull a few extra dollars out of your wallet – should we
be persuaded to do make the switch? I purchased most of my woodworking
machines back before any spiral cutterheads were available and I seldom
had the opportunity to use machines that were spiral-cutterhead
equipped. It wasn’t until I began using the Popular Woodworking Magazine
jointer that I experienced the difference. I was amazed by how much
quieter the spiral head turned out to be. Also, the idea of rotating a
carbide knife (one of many found on each cutterhead) instead of pulling
three knives from the standard setup, sharpening the group then
re-installing them into the machine while using dial indicator to get
the exact setting sounded interesting. But are spiral cutterheads worth
the extra investment?

If you search around the Worldwide Web for
information on spiral cutterheads, you’ll find limited resources that
contain bits and pieces information; some are valuable and some are not.
How are you to make a decision? Did you know that some spiral
cutterheads cut with a shearing action while others that could pass as
twins for the shearing designs have insert knives that meet the wood at
90 degrees just as a three-knife cutterhead does? And are these designs
that much better than the standard three-knife designs? Faced with these
questions and the same web sites to surf, I decided to dig deeper. It’s
time to uncover the ins and outs of spiral cutterheads.

To get
the straight poop, I didn’t have to go to the mountain. I had a short
drive South to Leitchfield, Kentucky. That’s the home of Byrd Tooling
and that’s where Shelix cutterheads were developed. (Shelix takes its
first three letters from the word shear and the last three letters from
helix – the knives are arranged in a helical layout and are set to
produce a shear cut.) Company owner Thomas Byrd gave me a tour of the
facility and answered all my questions. Nothing was off limits. I got a
look at the company’s tools and tooling methods – some of which are
proprietary and cannot be shared – and I walked away with a greater
knowledge of spiral cutterheads.

For example, when looking at
knives, are German-made cutters better than those made in other places?
Byrd tells me that whether the knives are German-made, produced in the
United States or created over seas, there is not much difference. (It’s
how they are sharpened that influences the cut.) Insert knives are
produced from sub micro-grained carbide and hold an edge that’s
comparable to high speed steel (HSS) knives. While the HSS
knives start sharper, after a few cuts they are on par with the carbide
cutters and it’s the carbide cutters that maintain a higher level of
sharpness longer.

Here’s on additional interesting fact. At Byrd
Tooling every insert knife is installed by hand. In the the 20″ planer
head and an 8″ jointer journal pictured above, there are 140 knives –
five rows of 20 knives on the planer head and five rows of eight knives
on the jointer head. Each knife is installed into the head using a
drill-driver (there is a special procedure to follow) then they go over
each knife a second time setting the perfect torque. (The wrench used is
shown at the right-hand side of the photo.)

On the down side –
and I hate to bust your bubble – no cutterhead is going to produce a
smooth surface that doesn’t require sanding or further finishing work
straight from your machine. Every cutterhead leaves small grooves –
three-knife designs leave those scallops across the board while the
spiral cutterheads create the grooves running the length of your board.
Also, there are no aluminum cutterheads produced for jointer or planers.
Any you see would be for shapers.

Here’s more information and questions:

• The space between the knives on spiral cutterheads act as gullets do on a handsaw or table saw blade.

• One of the real differences in cutterheads is the number of knives per inch of cut.

• Does a radius cutting edge produce a better cut than knives with rounded corners?

• What are single-effect spiral cutterheads?

Answers
to these questions would make a great magazine article, huh? We think
so. Look for the article in the February 2011 issue of Popular
Woodworking Magazine and subscribe now to make sure you don’t miss out.

— Glen D. Huey

To watch a video on making tapered legs using a jointer, click here.

For a book by John Kelsey “Jointer: The Tool Information You Need at Your Fingertips,” click here.

Or for a “quick hit” article on how to get a crooked board straight, click here.