Helix

A Helix is used to make objects like spirals, threads on bolts and screws, and springs. This two-part tutorial will show you the basics of creating a spring and then creating the threads on a bolt.

Procedure – Spring

To create a spring, you need a profile and an axis. Create the vertical line and the circle with dimensions shown here.

Fig.1 Profile and Axis for spring

Right Click in the graphics window. Choose Create Feature>Coil (as shown below).

Fig.2 Right Click>Create Feature>Coil

When the dialog box pops up, the Profile is already highlighted. The Axis button is depressed, which means that you need to pick the vertical line.

Fig.3 Coil Dialog Box

When you click on the axis, a sample of the coil will be visible. If it is headed down instead of along the axis, click on ,which will change the direction.

We now need to set the parameters to get the spring to look as it should.

Click On the Coil Size tab.

Click On the Type pull-down menu and 4 choices will appear.

Fig.4 Type choices

Note:

Pitch and Revolution: defines the elevation gain (pitch) for every turn (revolution) of the helix.

Revolution and Height: defines the number of turns (revolution) and the overall height of the helix.

Pitch and Height: defines the elevation gain (pitch) for every turn and the overall height of the helix.

Spiral: defined by the pitch and the number of revolutions.

For this exercise choose Revolution and Height.  Height: 1 inch, Revolutions: 5, Taper: 0.

 Fig.5 Coil Size Tab

Click on the Coil Ends tab. Here you will have 2 choices: Natural and Flat.

To get an idea of what both of them do, leave the Start at Natural and change the bottom to Flat, as shown.

Fig.6 Coil Ends Tab

Flat allows the spring to “stand on its end.”

The transition angle can be any number from 0 to 360 degrees. A Transition Angle of 90 means that the transition to flat will occur over a quarter turn, 180 means it will take a half turn to transition to flat, and so forth. Use 360 degrees for this exercise.

The Flat Angle value defines the extent of the flat coil end. For this, use 0 as shown.

Click OK, and the spring is made. Notice the top (where we ended) is flatter than the bottom (where we started).

 Fig.7 Finished spring

Procedure – Screw Threads

To create screw threads on a bolt, you need to have the bolt already created.

To save time, open the one that was done for you.

(This exercise is based on a ½ x 3 inch bolt, 13 UNC thread.)

Open File exercise Basic Hex Bolt.ipt.

Rotate the figure to see entire bolt.

Fig.8 Hex Bolt

Place a Work Axis and a Work Plane in the center of the cylinder.

Fig.9 Bolt with Work Axis and Work Plane

Note:

If you have difficulty with this, please review the tutorial on Work Features.

Choose the Work Plane as the Sketch Plane (remember to click on the edge of the plane) using the Sketch button .

There are several set-up steps to take to make sketching the profile (in this case a triangle) easier.

Right Click in the graphics window and choose Slice Graphics. This will “remove’” the material on one side of the work plane to make the bolt profile easier to see.

Fig.10

Fig.11 Bolt with Slice Graphics enabled

Next, at the bottom of the sketch tool bar, click on .

In order to correctly dimension and place the triangle we are going to draw, we need to “Project” the right side of the bolt onto the current sketch plane.

Click on the right side of the bolt. Notice how that segment is now darker.

Fig.12 Projected Geometry Highlighted

Draw a triangle with the placement and dimensions as shown below. The equilateral triangle is created at the end of the cylinder, and has sides of .095 inches in length.  Use a Collinear constraint to align the bottom of the triangle with the projected edge of the bolt.

NOTE: These dimensions are NOT the exact size that the threads are on a bolt; they are for “looks” rather than manufacture. Inventor has a part library of common fasteners which are anatomically correct.

Fig.13 Geometry and placement

As with the spring: Right click > Create Feature > Coil.

Choose the axis and make sure that the direction is correct. Click on the CUT button.

Fig.14 Coil Dialog Set up

Click on the Coil Size tab. Note that the choices are the same here as they were when creating the spring.

Choose Pitch and Height, with the dimensions as shown.

Fig.15 Coil Size Set up

Click OK. (This might take a while to accomplish depending on the speed of your computer.)

Note:

To turn “off” the work axis and the work plane, right click on each in the browser and uncheck visibility.

Fig.16 Finished Threads

Try This - Round over the head of the bolt

Place a new Sketch Plane on the existing Work Plane. (Turn the Work Plane and Work Axis visibility back on if you have turned them off.) Draw and constrain the sketch shown here in blue.  Project the geometry of the left and top edges of the bolt head onto the current Sketch Plane.  Make the top line of your sketch Collinear with the top edge of the bolt head, and make the end point of the sketch, where it touches the bolt, Coincident with the end of the top edge of the bolt head.  Apply the dimensions as shown.

Fig.17 Sketch for Round over

Revolve the sketch using the cut feature for the operation and a full rotation angle.

Fig.18 Rounded Head

Note: