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

Imperial Fastener Hole Size
(No Doweling Feature)

Fastener	Pin Diameter	Hole Size	Hole Tolerance	Positional Tolerance
#6	3.51	3.85	+/-0.05	0.2
#8	4.17	4.50
#10	4.83	5.15
1/4	6.35	6.65
5/16	7.94	8.25
3/8	9.53	9.85
1/2	12.70	13.00

Imperial Fastener Hole Size
(with Doweling Feature)

Fastener	Pin Diameter	Hole Size	Hole Tolerance	Positional Tolerance
#6	3.51	4.00	+/-0.05	0.2
#8	4.17	4.65
#10	4.83	5.30
1/4	6.35	6.80
5/16	7.94	8.40
3/8	9.53	10.00
1/2	12.70	13.15

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