Helical vs straight-knife cutterheads: insert counts and knife specs

Straight-knife cutterheads use two or three long knives, such as the DW735's three. Spiral and helical heads use many small inserts instead: 26 HSS inserts on RIKON's 25-130H and 74 four-sided inserts on Powermatic's 15HH. WEN says insert heads take smaller bites and cost more.

What is a straight-knife cutterhead?

WEN describes straight blades as the most common planer and jointer blade: long, straight knives that are easy to replace and leave a good general-purpose finish. (WEN Products)

DEWALT's DW735 uses a three-knife cutterhead at 10,000 rpm.

Felder offers the AD 741 with a standard 2-knife Felder-system cutterblock, and a 4-knife Felder-system and a 3-knife TERSA cutterblock as options. (Felder Group)

What are spiral and helical cutterheads?

WEN describes spiral blades as segmented inserts spaced evenly across the cutterhead instead of one continuous piece of steel. (WEN Products)

WEN uses "helical" for cutterheads with many inserts placed close together and arranged around the head in a helical pattern. (WEN Products)

Maker naming varies: Powermatic and RIKON call their insert heads "helical" or "helical-style", while WEN and Felder use "spiral". The counts below use each maker's term.

How many inserts do makers list?

On benchtop machines, RIKON lists 26 two-sided HSS inserts on the 25-130H planer, and WEN lists 26 staggered, rotatable HSS blades on the PL1326 planer. (Rikon Power Tools, Inc.; WEN Products)

RIKON's 8" 20-800H jointer lists 16 two-sided carbide inserts. (Rikon Power Tools, Inc.)

RIKON's 25-212H jointer-planer uses a 2-row helical head with 34 four-sided carbide inserts, sized 15mm x 15mm x 2.5mm. (Rikon Power Tools, Inc.)

Felder lists 63 knives on the Silent-POWER spiral cutterblock option for the AD 741. (Felder Group)

HSS or carbide, two-sided or four-sided?

WEN says many spiral inserts are two- or four-sided, so the cutting edges can be rotated for longer service life. (WEN Products)

Felder describes its Silent-POWER spiral cutterblock as using carbide reversible blades with 4-fold cutting edges. (Felder Group)

Insert material differs within a single maker's lineup: RIKON lists HSS inserts on the 25-130H and carbide inserts on the 20-800H. (Rikon Power Tools, Inc.; Rikon Power Tools, Inc.)

What do makers say about finish, noise and cost?

WEN says spiral inserts take many small bites instead of one large chomp, and describes the helical finish as superior. (WEN Products)

Felder says its Silent-POWER cutterblock cuts noise emissions by more than half when planing and gives usable blade life twenty times longer than standard blades. (Felder Group)

WEN says spiral-blade machines tend to cost more than straight-blade ones, and that helical cutterheads can cost more than an entire thickness planer. (WEN Products)

Taikra doesn't rank or test tools; every figure here is from the maker's own page or manual, linked.