In this step we will model the tap drill mounting holes in the front and top access.  Note: For machining purposes only a Point is required to perform a hole making operation.  We are only modeling the holes here for learning purposes.

1.Activate the .

2.To locate the center of the first hole you will draw two lines on the grid.  From the Curve Modeling tab select the Line command.

3.Draw the two lines shown below.  The first starts at the center and ends at the top left corner.  The second passes diagonally across two grid points bisection the first line at 90 degrees.

4.Now from the Curve Modeling tab select the Circle command.

5.For the circle center, activate the Intersect Object Snap from the Status Bar and then move the cursor over the intersection of the two lines until you see Int display next to the cursor and then select the intersection point.

6.For the circle diameter enter 0.1959 in the Command Window and press <Enter>.  This is the #7 drill diameter for a 1/4-20 tap.

7.Now you need 4 of these holes.  Let's use the mirror command to create the other three.  First select the circle you just created, then go to the Modify / Transform tab and select the command.
 
Note that the Modify / Transfer tab ONLY appears when an entity is selected!

8.From the Mirror selected objects dialog, the Number of selected objects should be 1, The Mirror Plane should be YZ Plane and box next to Create Copy should be checked.

9.Pick OK from the dialog and the circle will be mirrored and both circles should be selected automatically.  If not, select both of the circles and pick the command again.

10.This time from the Mirror selected objects dialog, the Number of selected objects should be 2, The Mirror Plane should be XY Plane and box next to Create Copy should be checked.
 
Note: You do not have to select the geometry first, as you can see this dialog has a Pick Objects button.

11.Now with all 4 circles drawn, all 4 should be selected automatically.  If not select them now.

12.Now go to the tab and select the Extrude Mesh command.

13.For the extrude length move the cursor to the and select the grid point at 0.500" in the positive Z direction or simple enter 0.5 in the command window and press <Enter>.

14.Now let's subtract the extrusions from the body to create the holes.  Go to and from the tab select the Subtract Mesh command.

15.For the first mesh solid select the body.

16.For the second mesh solid select one of the extrusions to subtract it.

17.Press the <Enter> key to repeat the command.  This time select the body and then the second extrusion.

18.Repeat the command two more time until all 4 extrusions are subtracted from the body as shown below.

19.Now we have 2 additional holes of the same diameter located in the top access.  Activate the .

20.Let's change the display mode for the Top View.  Select the Display menu from the View Toolbar in the Top View and select Toggle Shaded + Edges.

21.To locate the first hole, go to the Curve Modeling tab and select the Line command.

22.Pick the two grid points shown below for the start and end points of the line.  The line should bi-sect the two grid boxes from left to right as shown below.

23.Now from the Curve Modeling tab select the Circle command.  

24.From the Stats Bar activate the Mid Point Object Snap and deactivate all of the others.

25.For the center point of the circle select the mid point of the line you just created shown in the illustration above.

26.For the circle diameter enter 0.1959 in the Command Window and press <Enter>.

27.Now select the circle you just created and go to the tab and select the Mirror command.

28.From the Mirror select objects dialog the Number of selected objects should be 1, the Mirror Plane should be YZ Plane and the Create Copy box should be checked.

29.Now pick OK to mirror the circle.

30.Both circles should now be selected.  If not select them both now.

31.With the circles select go to the tab and select the Extrude Mesh command.

32.From the Status Bar activate the Grid Object Snap and deactivate the others.

33.Move the cursor down to the and select the grid point to set the extrusion length to 0.500" in the negative Z direction or simply enter 0.5 in the command window and press <Enter>.

34.Now select the two extrusions and go to the .  Make sure the Graphic Manipulator is toggled On.

35.From the Graphic Manipulator, pick the Blue Z Axis arrow and then enter 0.25 in the input window and press <Enter>.  The extrusions will translate up in the Z axis 0.25".

36.Now subtract them from the body.  From the Curve Modeling tab select the Subtract Mesh command.

37.For the first mesh solid select the body.  For the second mesh solid select one of the extrusions.

38.Press <Enter> to repeat the command and subtract the second extrusion from the body.