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.

14 thoughts on “Get the Skinny on Spiral Cutterheads

  1. Alex

    Another nice thing about the segmented cutterheads is that the shorter chips are easier to remove than long chips from the traditional head.

  2. Steve

    @Alan,

    I don’t think the insert radius is "optimized" for anything, because the radius used (4") is too small for any practical cutterhead diameter/helix angle combination. Instead, I think the inserts are radiused for the same reason that we radius plane irons: It prevents the corners from digging in and leaving "plane tracks."

    I don’t have personal experience, but I understand that some non-helical insert cutterheads _do_ leave plane tracks.

  3. Alan Schaffter

    Make sure you explain why the edges of a Shelix insert must have a curved cutting edges (hint: every point on the cutting edges "should" be the same distance from the center of rotation of the cutter head. That being said, all Shelix cutter heads use the same inserts, regardless of the diameter of the the head. How is this possible? Shouldn’t each head have its own insert with unique radius cutting edge? What diameter head are the inserts optimized for?

  4. Steve

    I think the discussion boils down to a simple question: Are you the kind of person that expects to get a ready-to-finish surface off the jointer or planer? If so, stick with steel knives, and keep them very sharp; in well-behaved wood, they will give a better finish than any carbide tool. On the other hand, if you’re the kind of person who is going to hand-plane or sand every surface before finishing, then a Byrd-style helical cutterhead is the better deal, because it does a very good job of flattening without tearout, even on impossible-to-plane woods.

    I was recently able to do a side by side comparison: I have a retrofit Byrd head in my jointer, but straight steel knives in my planer. I was working with some quartersawn curly cherry, which is very prone to tearout. There was essentially zero tearout on the jointer side of each board, but noticeable tearout on the planer side. Using my high-angle smoothing plane, set to take a moderately thin shaving (about 0.002"), it took two passes to remove the scallops created by the jointer cutters, but 6-8 passes to remove the tearout from the planer blades. Thus, for the way I work, the carbide cutterhead is clearly the better choice.

  5. Rob Cosman

    Hi Glen, didnt see this mentioned so thought I would bring it up. I bought the Byrd head for my 8" General on the advice of a friend that knows more about power tools than I ever will, David Eiason in London, Ontario. Was so impressed with the results I bought a Byrd head for my 20" General planer. The biggest advantage is also a slight problem. All other knives I have seen have the bevel on the back, opposite of the cutting direction. The carbide chicklets on the Bryd head have the bevel on the front, this changes the angle of attack significantly hence the vastly improved performance on figured wood. Try increasing the angle of attack (pitch) in your hand plane and notice how much harder it is to push thru the same piece of wood. I figure I would need half again as much horsepower to do the same work as a straight knife in my planer. The trade off is still hugely in my favor and I would never go back, just worth noting you cant take as big a bite as you could with straight knives. Good stuff always cost more and is always cheaper in the long run. Thanks to Byrd I no longer have to spend a dreaded 1/2 day changing knives. cheers
    Rob Cosman

  6. Chris

    Well, I have a spriral head in my jointer and planer and I have to say they are great. I would not go back for anything. Simple reason is the set up time and the amount to use I get before rotating any of them, mine are carbide. I hated changing the knives in my jointer and fiddling around to get the blades set right. Both my machine came with them,so I suppose I didnt have the retro fit issues some of you mentioned. Just my 2 cents.

  7. Josh

    One thing you don’t mention is the setup difference. I encountered this on my 6" delta jointer that I upgraded with a Byrd Shelix cutterhead.

    With straight knives, if the cutterhead is not perfectly parallel with the outfeed table, you can compensate when you align the knives with the table. For instance, if the front end of the cutterhead is lower than the fence side of the cutterhead (the case with my delta), then you can simply adjust all of the knives so they are perfectly aligned with the table.

    However, on a helical cutterhead, you can not perform this type of adjustment. You have to shim the cutterhead bearing supports in order to correct the misalignment (in my case one sheet of printer paper plus a single one dollar bill got me within about a thousandth of an inch). It was actually a bit of a pain in the butt to remove and shim the cutterhead multiple times to try different shim combinations (a straight edge, dial calipers, and feeler gauges got my close to start with, but it took several tries to get it right).

    I emailed Byrd prior to shimming the cutterhead to make sure I wasn’t missing something, they responded that it wasn’t an issue with their cutterhead it was an issue with jointer manufacturer and that I should take the issue up with delta. I have checked out a couple friends’ jointers and their tables aren’t perfectly inline with the cutterhead body either. I am guessing it isn’t something that the manufacturer spends much time or money on, since with straight knives it doesn’t matter as long as things aren’t grossly misaligned (I’m not sure how they deal with machines they manufacture and ship with helic heads).

    The helic cutterhead does cut significantly better then the straight knives now that I have it aligned. It runs quieter, causes less tearout, leaves a smoother surface, and its easier to change knives.

    Anyway, long story but wanted to share my experience since it wasn’t something I even considered to be a problem prior to dropping a healthy chunk of change on the cutterhead.

  8. Dreamcatcher

    Thanks for the reply, Glen.

    You are right, I do like old machinery just for the fact it’s old but I also like it because I can get a quality machine for a low price so it keeps my overhead lower… the reason I bought it in the first place was to lower my lumber costs. I don’t know any woodworking businesses that buy new… it’s way cheaper to scavenge from the big guys. It is very difficult to juggle overhead costs when you are just a small custom woodworking business; though if the right commission came in it could easily pay for the Byrd head in one shot. I am still on the fence but right now I am forced to stick with the stock clamshell head.

    Sorry to get the insert cost wrong. That was from a different brand (Grizzly) that I thought would be comparable. I just wanted to point out the math involved when comparing the maintenance costs of a blade vs. inserts.

    I also wanted to point out that there are other options out there when/if considering a different jointer or planer head; although it appears that Byrd dominates the replacement market making it very difficult to find search engine results for other brands.

    Maybe your article could shed some light on ALL the options one has:
    Hermance, Accu Max, Shear-Tec, Great Lakes Helicarb, Centrolock, Woodmaster, Shin Max, Format-4, Invicta, NAP Gladu Spiramax Sidewinder, Drake, Terminus, Global Tool, Tersa, Dispoz-A-Blade.

    Definitely check out that last one!

    Can’t wait to read the article.

  9. Glen

    I must say that I shouldn’t post blog entries late in the day on Monday. As Jon pointed out, HSS is high speed steel and not hardened stainless steel as I wrote. Also, the video link has been corrected.

    Dreamcatcher, I’m not sure where to begin. You have pointed out one of the issues when purchasing old iron – you have to spend money to rebuild and update old woodworking machines (I assume you enjoy that aspect as well as using the old machines). Also, a 12" jointer that is new has a selling price that is two to three times the cost of your Byrd cutterhead, so the percentages are not as great. Additionally, Byrd sells the replacement knives for $30.40 per box which is $3.04 each and not the $5.00 that you use in your comparison. Given your circumstances, a shelix cutterhead may not be for you, but for others making different decisions, a new cutterhead may be the difference between smooth boards and boards that look like Swiss cheese. Each of us has to make that determination.

  10. Dreamcatcher

    BTW:

    From my research there are straight knife heads, spiral knife heads (AKA: single-effect spiral cutterheads), straight insert heads, spiral insert heads (inserts cut at 90˚), and helical insert heads (inserts cut at 80˚).

    All types of spiral and helical heads are best for "pagan grain" wood like burl and birdseye. Spiral and helical insert heads are quieter than any blade head or straight head and since the cutting action is limited to such a small area, they only require a fraction of the horsepower that straight blades require.

  11. Dreamcatcher

    Ironic seeing this article today, I have been researching them all last week.

    I just purchased my first jointer (used). It’s a 12" C.O. Porter Co. Type ‘A’ circa 1915; a 1500 pound beast of a machine known simply as "The Porter".

    Unfortunately it’s so old it pre-dates the invention of wedged heads and currently has the more dangerous clamshell style head. Since it also has the old style babbitt bearings instead of modern ball bearings, finding a "plug and play" replacement wedge head is nearly impossible. My options are limited to machining a different head to fit, modifying the machine to ball bearings, or going with a Byrd Shelix head since they already make one to fit my machine.

    Then came the sticker shock……Byrd quoted me $1300.00 for the replacement head. That’s five times what I paid for the machine. After reading this article, it only confirms my feeling that they are overpriced. With modern CNC production machines like the one shown in the picture, where does the cost come from? It would cost me about the same to have a wedge head custom made from scratch by hand. Oh and while the Byrd head they would send me for that price has all the insert cutters already installed in it (why?) any replacement inserts are $5 each – sold as 10 for $50. By those calculations, a 12" jointer has $300 in cutter inserts. Considering that each one has 4 sides, that still relates to $75 per blade change on a standard knife head (unless your knives have two sides – which would then make it $150/change in comparison). Oh, and also consider that while an insert may have 4 sides, it is made of very brittle solid carbide so you really only get one nail strike per insert since they’ll shatter on impact. Heck, they’ll shatter when you install them if you don’t torque them exactly right. Of course you can buy their special torque tool for $120.

    Obviously I am still looking for viable options. At this point I might just stick with the clamshell head.

    DC

  12. Eric R

    I think you inserted a different video clip that the one you intended. The clip shows how to cut Cabriole legs on a band saw and doesn’t show anything about using a jointer for tapering legs.
    I also remember you advising a reader a while back that if they had a decent planer, that spending extra on the spiral cutter heads was probably unecessary.
    Thank you for the interesting article on how spiral cutter heads are made.

  13. Benoit Rochefort

    I remember using these carbide inserts on (professional) woodworking tools in 1988. These ranges from dado blades (used as a "nicker" on the side of the blade) for radial arm saw to a 24" planer (later… maybe in 1991).

    I however don’t remember if there were machines that uses them with a shearing cut.

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