Creating the helix in Solidworks...

We are all familiar with how to create a helix based on a curve. If you have never made one, here is the basic run down

1. Create a circle to drive the diameter of your curve

2. Open the Curve tool and choose the helix command (insert, curve, helix/spiral) Solidworks will automatically pick the open sketch, if is a circle.

3. Now we can choose how to control the helix.

-Pitch and Revolution

- Height and Revolution

- Height and Pitch

- Spiral (defined by pitch and revolution)

The helix's pitch can also be controlled with a constant, which I recommend, or a variable via a mini table. and finally clockwise or counter clockwise.

Now lets go back and create the same helix a different way.

1. Let just create a revolved surface 3" high and the radius is 1"

2. Now we need create a helix revolved surface which will fully contact our first revolve. This can be created by a swept surface. Be sure to sketch your path and profile long enough to insure full contact between the two surfaces.

3. Now comes the fun part! use the intersection curve command (Tools, Sketch Tools, Intersection Curve) and select the two surfaces. You will see a 3D sketch as a result.

4. Now hide both surfaces.

Why go through all this trouble?? because we can now edit the first revolved surface to any contour we want and create a variable diameter helix!

Hmm...kinda looks like a bed spring??

Unequally Disposed Profile Tolerance in Solidworks

The new ASME 2009 gives us the option to communicate a profile tolerance that can have an unequal value. This is communicated with "U" in a circle. For definition and information, please refer to para 8.3.1.2, and figures 3-11 and 8.1-8.3 in the ASME Y14.5 2009 standard (see below).

Solidworks 2011 will have this function available, but for those who are using an earlier version will need to do a little work around.

First we will need to edit a dimension or create a dimension we can delete later. In the dimension text editor navigate to the "more" button and select the circle alpha flag not "U". The editor will populate a code snippet . Copy (ctl c) that code. Navigate to the GD&T function and choose the profile symbol, insert (ctl-v) the code into the tolerance area of the feature control frame properties. It helps to put a space before and after the tolerance values. That's it!