Spiral planer heads
From the original questioner:
Why are they better? How difficult is it to rotate/change the carbide knifes? How long do they last in comparison to straight knifes?
It is hard to say how long they will last because so much of that depends on your product and how skilled you become at grinding.
You do not rotate the knife on the Newman-Whitney head. The knife is replaced with a new one.
I have customers who run their finish planers all day long--8 hours minus breaks and lunch. Many of these customers get 2 to 3 years out of a set of knives. But they are highly skilled in grinding and jointing.
Depending of the size of the planer that you are using, several types of cutter head designs are available. The Newman Whitney head is a very good choice.
On small planers, the use of insert cutters may be a better choice. Each application should be looked at before a decision is made.
Provide info on what wood species you are using and what the expected feed rates and moisture content are.
Dave Rankin, forum technical advisor
From the original questioner:
I will be planing glued up panels for the field of raised panel doors. I want a 24" machine, but have not bought one yet. The species will be red oak, hard maple, cherry and other lessor volume species. The feed rate will be determined by the quality of the cut. I want to level the panel and then run it through a 3-head sander. My goal is 220 grit finished.
I would generally outline the planer head differences as follows:
a) True helical insert head (Newman type) has considerable advantages in cutting geometry because of the extreme shear in cutting action, which tends to reduce tear-out, especially on difficult species. It is also re-grindable and can be jointed. Disadvantages include higher initial cost and the need for specialized grinding/jointing attachments on the planer.
b) Replaceable straight insert heads, or standard planer heads, are much lower cost, but need to be used sharp to minimize tear-out when cutting against the grain direction, or working with difficult species, and therefore need to be changed more frequently.
c) The new segmented insert heads (Drake type) have small inserts that are mounted in a spiral pattern flat to the tool surface. Since each insert cuts parallel to the axis of rotation, it does not have a true shearing action in cut. Advantages are lower initial costs and replacement costs for inserts. Typically these inserts have finer grain carbide with sharper cutting edge, because inserts are not brazed onto a holder as they are with the spiral head. Also, each insert can be rotated/replaced independently, which has considerable advantage when your wood has problems with surface grit or nails/staples. Disadvantages include the fact that they do not cut perfectly flat (each insert has a minute curve to overlap the next insert) and they cannot be reground or jointed.
I strongly recommend the true spiral head if your planer is equipped with grinding/jointing attachments; otherwise, the Drake type.
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