SolidWorks 2010 Bible

Chapter 7: Selecting Features

Variable pitch helix

You can specify the variable pitch helix either in the chart or in the callouts that are shown in

Figure 7.23. Both the pitch and the diameter are variable. The diameter number in the first row

cannot be changed, but is driven by the sketch. In the chart shown, the transition between 4 and

4.5 revolutions is where the pitch and diameter both change.

FIGURE 7.23

The variable pitch helix

Spiral .............................................................................................................

A spiral is a flattened (planar) tapered helix. The pitch value on a spiral is the radial distance

between revolutions of the curve.

Creating projected curves

Many users have difficulty envisioning the concept of the projected curve. The two options avail-
able for projected curves are

l (^) Sketch On Faces

Sketch On Faces ............................................................................................

These names can be misleading if you do not already know what they mean. In both cases, the

word sketch is used as a noun, not a verb, so you are not actively sketching on a surface; instead,

you are creating a curve by projecting a sketch onto a face.

Sketch On Sketch ..........................................................................................

The Sketch On Faces option is the easiest to explain, so I will describe this one first. With this

option set, the projected curve is created by projecting a 2D sketch onto a face. The sketch is pro-

jected normal (perpendicular) to the sketch plane. This is like extruding the sketch and using the

Up To Surface end condition. The sketch can be an open or closed loop, but it may not be multi-

ple open or closed loops, nor can it be self-intersecting. Figure 7.24 shows an example of project-

ing a sketch onto a face to create a projected curve.