Core Principle

The precision and cost of a hole are determined by its manufacturing method: drilling, reaming, or boring.

Drilling

• Fastest and cheapest method
• Used for clearance holes and pre-drilling for taps
• Tolerance: Typically ±0.1mm range
• Default assumption unless specified otherwise

Reaming

• Secondary process after drilling
• Achieves precise diameter and better finish
• Used for dowel pin holes and precision fits
• Tolerance: Can achieve H7 (±0.01-0.02mm)

Boring

• For large diameter holes or highest precision
• Very high positional accuracy and circularity
• Highest cost but highest precision (±0.005mm possible)
• Used when extreme accuracy required

Design Recommendation: Specify reaming only for precision fits like press-fit dowel pins. All other holes assumed drilled unless noted.