Standardising hole sizes across engineering designs offers several important advantages:

• Reduced tooling costs – Manufacturing facilities can maintain a smaller inventory of drill bits and cutting tools
• Improved manufacturing efficiency – Machine operators spend less time changing tools and can develop consistent processes
• Enhanced interchangeability – Components from different manufacturers or production runs can be used interchangeably when hole sizes are standardized
• Lower risk of errors – Using standard hole sizes reduces the chance of assembly mistakes or incorrect tooling selection

Metric Fastener Hole Size
(No Doweling Feature)

Fastener	Pin Diameter	Hole Size	Hole Tolerance	Positional Tolerance
M3	3.00	3.25	+/-0.05	0.2
M4	4.00	4.25
M5	5.00	5.25
M6	6.00	6.25
M8	8.00	8.25
M10	10.00	10.25
M12	12.00	12.25

Metric Fastener Hole Size
(With Doweling Feature)

Fastener	Pin Diameter	Hole Size	Hole Tolerance	Positional Tolerance
M3	3.00	3.45	+/-0.05	0.2
M4	4.00	4.45
M5	5.00	5.45
M6	6.00	6.45
M8	8.00	8.45
M10	10.00	10.45
M12	12.00	12.45

ELEVATE Your knowledge

Check out the links to see:

• How are these tolerances are calculated?
  A breakdown of tolerance stack ups calculating the hole size and geometric positional tolerance required.
• Example drawings
  See how these numbers should be displayed on manufacturing drawings