# Smart 3D Modeling Series: Parametric Bolt with Provision of Split Pin Hole - Blog 1of 3

In this blog series, we will create different variations of a parametric bolt based on variable size options and with or without provision for split pin hole. This will serve as another example of a parametric element that can be reused multiple times throughout a design due to variables and variations associated with it. (Refer to other blogs in Smart 3D Modeling series here.)

It should be noted that Constraints play a crucial role in creation of parametric elements. Only the correct constraints, when applied, will give you the desired result.

Following video demonstrates the end result that we will achieve at the end of this blog series:

In this blog we will create a basic 2D profile which can later be converted to a 3-dimensional bolt. For this, we will first create Variations with Variables for different sizes of bolts.

In a 3D Model, create the following Local Variables and Variations:

 Variable Expression (if any) Description R - Bolt Head Radius Head_Length R * 0.7 Bolt Head Thickness Chamfer_Equal_Distance (R/10) * 1.34 Length of Chamfer R2 R/2 Radius of Shank Shank_Length R * 3 Length of Shank

 Variations R (mm) M10 10 M12 12 M16 16 M20 20 M24 24 M30 30

You can either create these variables and variations manually or import them from the Bolt Variations and Variables.csv file.

Following are the steps to create the profile needed for the bolt:

1. In the Top view, create a circle with dashed line type and class set to Construction.
2. Now apply Dimension Element constraint, R and 2D Fixed constraint to the circle.
3. Set the ACS at the center of the circle. This fixes the point of placement as well as the point about which the parametric bolt will vary.
4. Draw a hexagon inscribed inside the construction circle. You can do this by using the Place Regular Polygon tool.
5. Apply the following constraints:
• 2D Coincident constraint to all the corners of the hexagon and the construction circle
• Equal constraint to the edges of the hexagon.
• 2D Fixed constraint to one of the edges of the hexagon (bottom edge in the image below).
6. Check if the hexagon adapts to the changes in the size of the construction circle, by changing the value of R.
7. Draw a concentric circle inside the construction circle. (Green circle, refer image below)
8. Apply the following constraints to the green circle:
• 2D Fixed constraint.
• 2D Concentric constraint with the construction circle.
• Dimension Element constraint, R for radius to make it the same size as the construction circle.

9. Draw a smaller, concentric circle (Cyan circle) inside the construction circle.
10. Apply the following constraints to the circle (Cyan):
• 2D Fixed constraint.
• 2D Concentric constraint with construction circle.
• Dimension Element constraint R2 for radius.

The basic 2D profile required to create the Parametric Bolt is now ready. In the next blog we will create a 3D bolt from this basic 2D profile. Stay tuned for the next blog which will be posted in the week of April 24, 2017.