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Shaper Cutter Performance Specifications

This article applies to shaper cutters, moulder heads and knives, and insert shaper cutters. All of these tools are designed to remove or shape large sections of material in a single pass. As such, careful consideration should be taken when setting up and running these applications. With that said you can find recommendations, formulas, and specifications on proper feeds and speeds within this page.


Formulas & Definitions

If any of you have read the section on saw performance you will find this section very familiar. That is because the theories are almost identical between saws and cutters with only Chip Load and RPM's being remarkably different. Cutters run faster and remove more material than a saw blade is capable. That said you must always take into consideration the safety of every setup to prevent injury or damage to you and your equipment. Cutters designed for use on shapers may not be the best configuration for use on moulders and vise versa. With that disclaimer here are the formulas and definitions.

Variable Definitions

  • RPM = Rotations per Minute

  • Chip Load = Material Removed by Each Cutting Edge in Inches

  • Feed Rate = Rate which the part is feed into the cut in Feet per Minute

  • Diameter = The Distance from the center of tool to the farthest cutting edge multiplied by 2.

  • p (Pi) = 3.14159265358979323846 (Round as Necessary)

  • Rim Speed = The speed in feet per minute that a tool spins at its diameter

  • # Wings = The number of teeth in the cutting tool


Feed Rate = (Chipload x # Wings x RPM) / 12

RPM's = (feed rate x 12) / # Wings x chip load)

Chip Load = (Feed Rate x 12) / (RPM x # Wings)

Rim Speed = (Diameter x p x RPM) / 12

As you can see all of these formulas are interrelated in that some of the information from one formula is required to use the other. This can be a real problem if you don't have enough information up front. So to make this process easier we have included a very useful chart below

Recommended Chip Loads for Cutters

Finish Requirement

Low   High
Fine Finish 0.010 to 0.030
Medium Finish 0.030 to 0.100
Course Finish 0.100 to 0.200

Chip load is the most important piece of information that most machine operators do not know. With this information you can calculate feed rate and RPM, but it helps to know the RPM's your machine is capable of. This will give you a good base to specify the feed rate of your application. Since most moulding and shaping applications are done in the with grain direction this chart is relatively simple. You simply pick a finish category and then decide on how far up or down the range your application requires. Once you settle on a chip load specification you can proceed to running the formulas using the known information.

These formulas are only the starting point to figuring out your exact specifications. They will give you a good base point that will provide a good combination of tool life, material finish, and efficiency. However, always consider the human factor as well. Will the men feeding and unloading be able to keep up with the machine? Will a shaper operator be able to feed at the specified speed? Can a shaper operator hold the part at the RPM specified?

Always work safe. Not just fast.


Hook Angles

Now I would like to address a seldom mentioned dimension in most shaper cutters and moulding tooling. Hook angle is the degree of angle that each cutting edge encounters the material during the cut. This has been called rake angle and attack angle in the past, but they are all the same thing. Many times a difference of only five degrees in the hook angle can improve the finish of the cut dramatically. Hook angle is mainly dependant on the material being cut and the state of dryness it is in. It is advisable to specify the hook angle when ever you order tooling for any application. This can be especially important if you are running dual hook knife heads and you plan on running one hook or the other. To make it easier to specify hook angle the following chart has been supplied.


Hook Angles

  Degrees Degrees
Species Kiln Dried Wet or Green
Ash 10 15
Basswood 10 20
Beech 10 15
Birch 10 15
Cedar 20 10
Cherry 10 15
Chestnut 5 10
Cottonwood 5 10
Cypress 5 10
Elm, Hard 0 5
Fir 15 15
Gum 20 25
Hemlock 15 20
Hickory 5 10
Mahogany 10 15
Maple 5 10
Oak 10 15
Oak Qtd. 10 15
Pine, Yellow 20 25
Pine, White 20 30
Pine, Ponderosa 20 30
Poplar 20 35
Redwood 5 15
Spruce 20 25
Sycamore 5 10
Walnut 5 10
Elm, Soft 5 10


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Cutter Performance & Specifications