Step 1: Create a cylinder of 20 mm diameter x 7.5 mm height.
Step 2: Create a hollow cylinder of 17 mm diameter x 8.5 mm height. It is important to lift 1.5 mm from the workplane.
Step 3: Align both cylinders. Group it.
Step 4: Select the cube and create a rectangle of 24 x 7 x 7.5 mm.
Step 5: Align Rectangle and Cylinder, put the rectangle tangent to cylinder.
Move the rectangle with the arrows on the keyboard and put tangent to the cylinder.
Step 6: Ungroup Cylinder
Step 7: Group cylinder, hollow cylinder and prism.
Step 8: Create a hollow cube of dimensions 24 x 7.5 x 2 mm. Raise it 3.75mm from the workplane.
Step 9: Align hollow cube tangent with whistle. It may be necessary to adjust the grid to 0.1mm. and Group it
Step 10: Duplicate Hollow cube and Rotate -22.5º the hollow cube.
Step 11: Put that hollow cube tangent to the hollow interior of the whistle. It may be necessary to adjust the grid to 0.1mm.
Step 12: Create another Hollow cube of 24 x 3 x 7.5 mm, raised 3.75mm from the workplane.
Step 13: Place New cube & Group all and you have one half of the whistle.
Step 14: Duplicate it to get the other half of the whistle.
Step 15: Invert the duplicated half using the Mirror tool or by pressing ‘M’ key.
Step 16: Invert the Half Turn 180º the Inverted Half
Step 17: Align the Two Halves to the Center.
Step 18: Mount one half on the other by raising it 7.5 mm and group it.
Step 19: To create a Keyring, create a 12x12x mm toroid raised 1.5mm from the workplane
Step 20: Remove half of the toroid you do not want with a hollow cube.
Step 21: Place that half of the toroid to the body of the whistle. Check that toroid and whistle are aligned perfectly.
Step 22: Group It and Whistle is prepared.