Final answer:
Equally spaced holes on a bolt circle should include the number of holes, the bolt circle diameter, and the size of the holes, with evolved guidelines suggesting larger margins for thread engagement depth.
Step-by-step explanation:
To dimension equally spaced holes on a bolt circle, you should indicate the number of holes, the diameter of the circle on which they lie, and the size of the holes. The bolt circle diameter is typically given with a dimension, and from a single hole, an angular dimension specifies the position of the other holes.
For instance, for a circle with 6 holes, a note might indicate '6 HOLES EQUIDISTANT ON A Ø 100 PCD' (PCD stands for pitch circle diameter). If the holes are through holes, the depth is not applicable.
However, when considering tapping holes, the 'rule of thumb' has evolved from 5 times the diameter side-to-side and 7-8 times the diameter in depth, to allowing for even larger margins like 8 diameters side-to-side and up to 15 diameters deep for enhanced strength and stability.
This ensures that the thread engagement is sufficient for the load that the bolted connection will need to bear.