Baffled by "Spiral" Carbide Jointer Heads

[Wayne Cannon]

Looking at photos of spiral carbide jointer heads, I am baffled by the emphasis on "spiral" and associated claims.

In all photos I've seen, it appears that the cutting edges are still parallel to the axis like conventional joiner blades. If my geometry isn't failing me, this means that there is no slicing effect (like running a plane at an angle, or using a spiral router bit) to effectively lower the angle of attack.

I understand the carbide-versus-steel benefits, the ability to change/rotate individual cutters, and the more balanced cutting (dozens of tiny cuts per rotation instead of two or three big cuts per rotation).

At least one company makes jointer heads with true spiral blades -- continuous lengths of steel -- that have the slicing effect, but they are expensive.

Am I missing something about this "spiral" thing?

[Steve Nouis]

Byrd make a head where the cutters are a a angle to the bed. Some others don't. Steve

[Jeff Duncan]

I can't tell you how it works on an engineering level. But I can tell you it works. I had one for about a year and the difference can be appreciated by even the most novice of woodworkers. The fact that it did work was good enough for me not to care to much about the geometry of what made it work.
I'm sure someone will come along with more knowledge than I have that may be able to help you out.
good luck,
JeffD

[glenn bradley]

Am I missing something about this "spiral" thing?

In a word, yes. There are spiral knives; those that are one cutting edge end to end and are oriented so that they shear the cut. There are spiral patterned, indexed carbide insert heads that are many cutting edges oriented perpendicular to the travel of the material so that there is at least one cutterhead in contact with the material at all times (or thereabouts). These insert heads and others provide four cutting edges per insert increasing the value of the method.

There are spiral patterned indexed carbide insert heads that are many cutting edges oriented at a shear angle to the travel of the material so that there is at least one cutterhead in contact with the material at all times (or thereabouts) AND they perform a shearing action.

There are "spiral" heads being introduced by SteelCity that use indexed, perpendicular carbide inserts but in a much less dense pattern. All these heads are designed to provide better performance in figured woods. They are quieter, longer lasting in the case of multi-sided carbide and require no height adjustment once aligned (or thereabouts).

[Peter Quinn]

Take a look at the BYRD SHELIX heads, these have the shearing action and the associated benefits of a spiral index head. It seems many of the copies set their knives in a spiral or 'helix' but don't include the 'S" or shear cut as you have noted.

I use a spiral planer at work that uses very thin flexible knives which are set in a spiral head and produce a true shear cut. This is the older spiral format, I think Shelix is intended to be an improvement on this concept.

For example, we have an 18" Powermatic with terminus head (4 straight knives), so loud you can barely stand it with head phones on, tear out can happen on figured wood or difficult grain changes. The spiral head planer is a Casadei 24", with SHARP knives, grain direction is irrelevant, it does not tear out. It is so quiet you can operate it without ear protection, though I do not, and the surface quality is so fine you can begin sanding at 150 grit. The knives are HSS and don't last long in a production environment. Dull knives are a bit louder, tear out becomes annoying even on wood that should be straight forward to plane, surface quality is so bad everything must pass through a wide belt.

[Cliff Rohrabacher]

U get what U pay for.
It's really that simple.

[Walt Caza]

Hi Wayne,
The distinction is clear, shear angle lowers the effective cut angle.
Same benefit as skewing a handplane.
Better handling of tricky grain, pagan, end and reversals.
(I just wanted to say pagan, have been waiting a long time)

Specifically, Byrd heads offer shear-helix, thus shelix.

In the real world, I no longer pay much attention to reading grain before
feeding it through, with good results.
Also, I can now speak over my planer without shouting.
Much less fatigue-ing for long dressing sessions.

Also, the Byrd turds facilitate entrainment in the air flow of dust collection.
HSS may start a bit keener, but carbide proves more durable over time.
I am trying not to overstate it, because my conviction in the superiority
of the Byrd heads is high, and you might wonder if I'm nuts!

Here is a link to an old thread about my planer head.
There are 2 sets of 4 pics. The second set shows how the carbide inserts
meet the wood at a shear angle.
http://www.sawmillcreek.org/showthread.php?t=71399


Scallopping has been a non-issue for me, as I sand everything anyway.
Shelix has been great on my 15" planer.
I cannot wait to also upgrade my 8" jointer to Byrd as well.
take it easy,
Walt

[Russ Massery]

Ditto on Walt's Reply, Except mine's in reverse I have a Bryd head in my 8" jointer and can't wait to install one in my planer.

[Frank Drew]

I don't think OP Wayne was asking about the benefits of the newer cutterheads; unless I misunderstood him, he said that the pictures he's seen seem to show straight knives on what are supposed to be "spiral" head machines ("the knives are still parallel to the axis [of the cutterhead, I assume] like conventional jointer blades.").

[Eddie Darby]

In all photos I've seen, it appears that the cutting edges are still parallel to the axis like conventional joiner blades. If my geometry isn't failing me, this means that there is no slicing effect (like running a plane at an angle, or using a spiral router bit) to effectively lower the angle of attack.

I think you are seeing the Grizzly head that has the carbide cutter's edges in the same configuration as a straight blade.

The Byrd Shelix head has the carbide cutters slanted at an angle to make it more of a shelix action.

Skewing a 'handplane' does not work in all situations, such as when planing wild grain wood. Here one needs to increase the angle of attack, rather than decrease it with a skew of the 'handplane'. So a 'handplane' has the advantage of quick easy variable geometry to match each situation.

I am sure that there are performance differences between the Byrd Shelix Head and the Grizzly Straight Head with varying woods. It is just a question of how much difference.

[Wayne Cannon]

Thanks to everyone for the clarifications. It seems that all of the various configurations are available.

The Byrd Shelix looks most interesting. Reading threads elsewhere on the Internet, there was conflicting information regarding whether the head-segments had straight versus curved cutting edges.