This instructable assume that the user:
1) can create primitives, such as cubes and cylinders.
2) is acquainted with the use of constraints.
Step 1: Create a Cylinder
In this example, I used a 6mm x 50mm cylinder.
Step 2: Create a Cutting Tool.
1) Create an equilateral triangle.
Note the equal constraint used on each leg of the triangle, as well as the vertical constraint on the outside leg.
2) Dimension the distance from the center to outside leg as the radius.
Helpful Hint: by using the Equation Editor, you can set the dimension to diameter/2; then the cutting tool will follow the diameter of the cylinder if you make any changes
3) Dimension the size of the cutting tool to slightly less than the thread pitch.
This is very important, as this will keep the helix from overlapping when it is created and giving an error.
Step 3: Create the Helical Cut Feature
If I was thinking a bit clearer, the height parameter would be equal to the distance of thread I wanted, plus one more pitch length, but you can be sure to do that to yours... :)
Step 4: Making It Look Good... or Is That Well?
Step 5: Select the End of the Cut
From the Toolbar, select Project to sketch.
Hint: If you choose Maintain associativity, the new sketch will follow the face if it changes.