Helical Head Cutters
For Jointers and Planers
Q&A
1.Primary difference between straight knifecutters versus the spiral helical head cutters in jointers and planers. The “true” helical head planers and jointers such as are on the Powermatic and JET planers have a total different cutting approach over the straight knife cutters or other competitors with carbide insert tooling. The unique geometry of the carbide inserts as well as the 14 degree skew of the insert to the cutting surface produces a shearing type cut versus “chopping” type cut as found with all other planers in the market.
2.Are straight edge cutters more apt to have ridges than helical head cutters? Yes, both straight knife blades and square carbide insert cutterheads from the competition are more prone to this issue. Straight knife blades that receive a knick while in use will almost always knick all the knives in cutterhead in the same spot relative to the rotation of the cutterhead. This generates raised lines in the boards after planning which must be removed by secondary sanding. The same thing can happen on the competition’s square carbide insert when indexing a single, non-perfectly square insert. The uneven insert will create a “witness line” from the flawed insert in the surface of the board. Although these lines most often are dimensionally negligible, the burnish effect or texture change in the board must be removed before finishing or it will be highly visible in the finish operation.
3.Noise level: Straight cutting heads versus helical heads. By virtue of the true helical cutterheads used in the Powermatic and JET jointers and planers, the noise level is dramatically reduced due to a shearing type cut occurring on the wood versus the chopping type cut on the straight knife. The airflow around the helical head is a much different acoustical situation also. The loud drone of the cutterhead on many planers is due to the air cavitations around the straight blades and the chip deflectors which is not present on the helical design. The helical heads will most likely operate at a lower volume than the dust collector servicing the planer and allow a normal conversation to be held while planning lumber.
4.Regardless of cutterhead type, won’t all boards running through a planer or jointer still require some degree of sanding? Most often sanding on planed boards is done to remove the very fine ripples left from the straight knives or various amounts of tearout from difficult grains directions in the wood planed. If neither of these exists, as is typically the case with helical head planers, then sanding can be relegated to simply achieving a constant surface texture with all mating pieces of a project.
5.Are the cutters solid carbide or carbide-tipped? The inserts are solid micro-grain carbide which are 15 millimeters square and have 4 cutting edges per insert.
6.What are the advantages of carbide blades versus high-speed steel? High speed steel knives will have a knife life often a whole order of magnitude lower than carbide knives. For instance a typical M2 tool steel knife may only last 1/10th the time under the same circumstances as a carbide knife.
7.What grade of carbide are the blades? C1, C2, C3, C4? Does a softer grade of carbide produce a better cut? What are the tradeoffs? The inserts used in Byrd helical cutterheads are a special blend of carbide well suited for the woodworking application. It is a micro-grained carbide with a high cobalt content to balance toughness and hardness for long life. The micro-grain structure allows it to be ground to a keen cutting edge. The special carbide is most closely related to C4 carbide.
8.What is the recommendation for sharpening cutters? Is it more cost-effective to replace? Can a do-it-yourselfer tackle this project or is it better left to a professional sharpener? What’s the procedure for replacing cutters? Due to the fact that each insert has four cutting surfaces and the special geometric grind of the knife, sharpening is not economically feasible. It is recommended to replace the inserts after four indexes in the cutterhead. This is typical protocol from the metalworking industry by which this technology is derived. Replacing and/or indexing the inserts is a simple matter of loosening the Torx head screw, rotating or replacing the knife and tightening back down. The knife auto-seats in position and needs no knife setting gauge or special technique or procedure.
- Does every helical head have 150 four-sided cutter knife inserts? The amount of rows and cutters per row yield the number of insert per head. The following is a list machines with their rows of cutters and number of inserts.
Powermatic
MachineRowsTotal inserts
54A Jointer 640
PJ-882 Jointer 654
15HH Planer 698
209HH Planer 6 132
201HH 6 150
JET
MachineRowsTotal Inserts
JJ-6HHDX 427
JJ-8HH 436
JWP-15HH 468
JWP-208HH 492
10.Changing knives: Should knives be changed all at once, only in areas showing marginal board finish results or both? Insert are typical indexed if a couple inserts have received damage from a steel or other non wood materials. Since damage is usually contained to only a couple inserts, a simple rotation of the affected inserts is necessary. Only after thousands of board feet of planing would a rotation of all inserts be recommended. In a hobbiest or non-production environment, this thresehold may never be reached.
11.The Byrd Shelix cutters versus the Terza, Terminus or Whitney cutterheads? All of the aforementioned represent various configurations of the straight knife cuterheads. The are variations of knife holding methods and and types of steel for the knife. Nevertheless, they all have the same pitfalls of straight knives mentioned in the previous answers.
12.Should shops consider having a wide-belt sander to address planed boards? A widebelt sander would probably have utility in any shop. Sanding intended to address the issues of straight knife planers would be, for the most part, eliminated. A widebelt would have utility in sanding wide panels beyond the width capacity of the helical head planer.
13.What are the advantages of running into a nail or staplein the board with a helical head versus a straight line cutter? The most notable advantage would be the containment of the damage to only a single insert or a small number and the ability to index the small amount of inserts very quickly. A straight knife must be ground along it’s whole length to a point that corresponds to the bottom of the knick. This dramatically shortens the useful life of all the knives in the cutterhead. Due to the fact that the inserts are carbide, many situations that damage straight tool steel knives don’t damage carbide in the same circumstance. Some times very hard knots in the wood can damage the cutting edge of straight knife and not likely to affect carbide.
14.Does Powermatic use Byrd cutting heads or is it an OEM custom Byrd cutting head? If someone was buying the Byrd Shelix cutterhead as an aftermarket replacement, is it identical to the cutterhead used in Powermatic? Powermatic uses actual Byrd cutterheads in the 15” and 20” planers. The rest of the helical line-up for both brands uses the same design but manufactured in Asia.
15.When you factor in the cost of a new jointer or planer, what percentage of the cost ties back to the cutter head assembly? Approximately 1/3 of the cost of the jointer or planer is associated with the helical cutterhead alone.
- Why buy a Powermatic jointer or planer versus Grizzly or General? The Powermatic and Jet cutterhead have a true helical design whereby the cut is shearing versus a straight chopping of wood. The benefits of shearing are far reaching including surface finish, noise level and knife life.