2. Holes 3 Basic Types Drilled - Straight Cylinder
Counterbore - Two cylinders, one on top of the other. Used to receive a bolt head.
Countersink - A cone on top of a cylinder. Used to accept a flat head bolt/screw.

3. Hole Types Hole Counterbore - receives a bolt head
Countersink - receives a flat head screw or bolt

4. Hole Feature Placement
A hole feature requires a hole center point sketched on an existing feature. You can also select endpoints or center points on existing geometry as hole centers.

5. Threaded Holes
Threads can be added to holes for bolts or screws. There are several types of threads series. Each is identified by their:
Major Diameter
Threads Per Inch
Thread Series Identification
Ex. 9/ UNC
This represents a thread with a major diameter of 9/16”, 12 threads per inch and is a standard Unified National Course thread.

6. Unified And American Threads
Thread Annotations
Unified And American Threads
UNC - 2A _ .75
Major Diameter
# of Threads per Inch
Thread Series - UNF, UNC, UN, UNR
Class of Fit
1=large tolerance , 2=General purpose, 3=low tolerance
A=External, B=Internal
Blank=Right hand, LH=Left Hand
Thread Depth - Internal

7. Thread Patterns UNF - Unified National File
UNC - Unified National Course
UNS - Unified National Special
UNEF - Unified National Extra Fine
ISO - International Standards
UN - American National (External Thread)
UNR - American National (Internal Thread)

8. Unified National Thread Form
Depth
Rounded Root
Pitch

9. American National Thread
Depth
Pitch
Flat Root
Very similar to Unified National Threads but has a Flat Root.

10. Metric Thread Forms - ISO
Depth
Pitch
Flat Root

11. Thread Annotations ISO Thread Forms M12 X 1.5--6H
# Between 3 & 9 identifies grade of tolerance
3 - 5 Fine, 6 is most common, 7-9 Course
Letter Denotes Thread Tolerance H=low, G=tight
H or G for Internal, g or h for External
Thread Pitch in millimeters followed by a dash
X means by
Nominal Major Diameter in millimeters
Designates Metric