Festool PD561287 User Manual

 

20 

Kapex KS120 Miter Saw 

Compound miter cuts are where the saw is both in a miter 

position and a bevel position at the same time. There are 

several applications for compound miter cuts, but cutting 
crown moulding and sloped miters are common examples. 

The example below shows a very simple birdfeeder roof. 

The greatest challenge with compound miters is 

determining the proper saw settings to achieve the desired 
miter angle. These saw settings can be found in look-up 

tables for standard mouldings, but for non-standard 

angles, determining the proper saw settings requires 
mathematical calculation. 

 

Note that there are several methods for 

accurately cutting crown moulding depending on 

the circumstances. Make sure to review the 
methods described in the applicable section on 

page 21. 

Calculating compound miter settings requires two 
parameters from the desired joint: the corner angle and 

the slope. 

The corner angle is the angle between the two pieces, 

when viewed looking straight down on the joint. The 

corner angle is relatively easy to determine, but it is also 

the value that can cause the greatest amount of confusion 
for many woodworkers. That’s because most woodworkers 

view angles differently than a mathematician will. A 

woodworker typically considers both inside and outside 
corners as 90 degrees (with a 45 degree miter) even 

though a mathematician would make the distinction that 

one corner is 90 degrees and the other is 270 degrees. To 
be consistent with miter saw settings, the corner angle is 

measured from a straight line between the two pieces, as 

shown above. 

The Slope angle is the angle that each piece makes with 

respect to the base of the corner, such as the ceiling or 
floor in the examples provided here. For a roof-like 

structure, this would be the pitch of the roof. 

For crown moulding, this would be the 

compliment of the “Spring Angle” of the 
moulding. Common spring angles for 

mouldings are 38/52 and 45/45. 

The corner angle for standard polygons is 

shown in the table on page 18. 

For non-standard corner angles, such as a 

room that is slightly out of square, the 

MiterFast tool can be used to determine the 

corner angle. To use the MiterFast tool to measure 

the corner angle, follow the “

Using the MiterFast Tool

” 

procedure on page 15, but instead of making the cut, 

record the saw’s miter setting angle. This angle is ½ the 
corner angle, so multiplying by 2 will give you the corner 

angle. (The compound angle calculator on page 21 also 

has an option for letting you enter this angle directly 
without needing to double it.) 

A polyhedron is a pyramid that can have any number of 
sides. The easiest method for determining the slope of the 

polyhedron is by measuring the Drop and Projection of 

one face. These are the distances from the center-to-the-

edge, and the base-to-the-point of the pyramid. Note that 
with a polyhedron with an odd number of sides, the center 

is found by drawing bisecting lines as shown in the image 

below.