Machinist Drilled Hole Tolerance Capabilities Chart per. AND10387

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Machinist Drilling Mechanical Tolerance CapabilitiesChart - ANSI Size Drills, ISO Metric Drill Sizes

Drilled hole locations and size variations are cumulative of several manufacturing variables. Tool sharpness, accuracy, tool and machine rigidity, machine spindle bearings wear, general quality of machine, use of drill fixtures, material thermal expansion, and material density variations are some to the reasons hole features will never be manufactured perfect.

Most commercial twist drills have a diameter slightly smaller than the stated nominal size, however the actual hole feature will likely be manufactured larger than the nominal size of the drill tool. Compensating for manufacturing tool and process variability is a significant challenge for tight tolerance holes.

Related: Drilled Hole Tolerances per MIL-HDBK-727 Design Guidance for Producibilty

For Drill size chart for both Metric and ANSI sizes see:

Machinist Drill Sizes - ANSI Size Drills, ISO Metric Drill Sizes

Comprehensive guide for proper design of geometry, process capabilities & proper mechanical tolerance specifications.

Related: Engineering Design for Manufacturability

Per. AND10387
Airforce Navy Aeronautical Design Standard

These size and tolerance are for holes drilled with a drilling machine using suitable jigs and fixtures. The hole tolerances depend upon the diameter of the hole and increase as the hole size increases. The following are standard tolerances for general machine work and apply in all cases except where greater or lesser accuracy is required by the design. Drilled Hole Size Tolerance
.0135 THRU .125 +.004/ -.001
.1260 THRU .250 +.005/ -.001
.2510 THRU .500 +.006/-.001
.5010 THRU .750 +.008/ -.001
.7510 THRU 1.000 +.010/ -.001
1 .001 THRU 2.000 +.012/ -.001

Mechanical location tolerance capabilitiesChart

Minimum Recommended Position Tolerances for Location of Hole Features in (mm) Less than 1" (25.4mm) in Diameter *
Method Normal Tolerance inches (mm) Tight Tolerance inches (mm)
Manual location techniques (center punch and drill) .080 (2) .020 (0.5)
Drill fixture using bushing .025 (0.635) .008 (0.2)
Precision milling or CNC machine with fixture .016 (0.41) .008 (0.2)
Precision milling or CNC machine with optical or precision orientation .005 (0.13) .003 (0.076)
Jig boring with optical or precision orientation .002 (0.025) .0005 (0.013)

* # .xxx is roughly equal to [ xxx = Positional Tolerance x .356 ]

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