Through Hole, Blind Hole and Counterbore*
| Size Ranges (Inch/Metric) |
||
| Above | Thru & Including |
|
| LOW Magnification For 1260:1, 2500:1, 4000:1, 5000:1 & 8000:1 |
.123"/3.1mm+ | .185"/4.7mm |
| .185"/4.7mm | .248"/6.3mm |
|
| .248"/6.3mm | .3735"/9.4mm |
|
| .3735"/9.4mm | .540"/13.7mm |
|
| .540"/13.7mm | .825"/21.0mm |
|
| .825"/21.0mm | 1.135"/28.8mm |
|
| 1.135"/28.8mm | 1.484"/37.7mm |
|
| 1.484"/37.7mm | 2.010"/51.1mm |
|
| 2.010"/51.1mm | 2.510"/63.8mm |
|
| 2.510"/63.8mm | 3.004"/76.3mm |
|
| 3.004"/76.3mm | 3.510"/89.2mm |
|
| 3.510"/89.2mm | 4.010"/101.9mm |
|
| 4.010"/101.9mm | 4.500"/114.3mm | |
| HIGH Magnification For 1000"1, 16000:1, 20000:1 & 32000:1 |
.062"/1.6mm | .093"/2.4mm |
| .093"/2.4mm | .123"/3.1mm |
|
| .123"/3.1mm++ | .185"/4.7mm |
|
| .185"/4.7mm | .248"/6.3mm |
|
| .248"/6.3mm | .365"/9.3mm |
|
| .365"/9.3mm | .540"/13.7mm |
|
| .540"/13.7mm | .825"/21.0mm |
|
| .825"/21.0mm | 1.135"/28.8mm |
|
| 1.135"/28.8mm | 1.484"/37.7mm |
|
| 1.484"/37.7mm | 2.010"/51.1mm |
|
| 2.010"/51.1mm | 3.004"/76.3mm | |
3-4.7mm/.123-.185"![]() Minimum recommended hole length: 4.8mm/.187in |
14.1-37.8mm/.588-1.484"![]() Minimum recommended hole length: 6.35mm/ .250in With guide sleeve or stop collar: 1.77mm/ .070in May be used with AHA-4 or -5 Extensions for deep holes. |
4.7-6.3mm/.185-.248"![]() Minimum recommended hole length: 4.8mm/ .187in |
37.8-76.5mm/1.484-3.004"![]() Minimum recommended hole length: 6.35mm/ .250in With guide sleeve or stop collar: 1.77mm/ .070in May be used with AHA-4 or -5 Extensions for deep holes. |
6.3-9.5mm/.248-.3735"![]() Minimum recommended hole length: 6.35mm/ .250in With guide sleeve or stop collar: 1.8mm/ .070in |
|
9.5-14.1mm/.3735-.588"![]() Minimum recommended hole length: 6.35mm/ .250in With guide sleeve or stop collar: 1.77mm/ .070in May be used with AEX-1 or -2 Extensions for deep holes. |
76.5-114.3mm/3.004-4.50"![]() Minimum recommended hole length: 6.35m /.250in With guide sleeve or stop collar: 1.8mm/.070in |

3.9-4.7mm/.155-.185"![]() Minimum recommended hole length: 6.35mm/ .250in. Note: Masters must simulate workpiece for holes of this size. |
11.8-14.1mm/.467-.556"![]() Minimum recommended hole length: 6.35mm/ .250in. Shorter bores can be checked. Consult Mahr Federal Customer Resource Center. May be used with Extensions AEX-1 or -2 for deep holes. |
4.7-6.3mm/.185-.248"![]() Minimum recommended hole length: 6.35mm/.250in. |
14.1-37.8mm/.588-1.484"![]() Minimum recommended hole length: 6.35mm/ .250in. Shorter bores can be checked. Consult Mahr Federal Customer Resource Center. May be used with AHA-4 or -5 Extensions for deep holes. |
6.3-9.47mm/.248-.373"![]() Minimum recommended hole length: 6.35mm/.250in Shorter bores can be checked. |
37.8-76.5mm/1.484-3.004" ![]() Minimum recommended hole length: 6.35mm/ .250in. Shorter bores can be checked. Consult Mahr Federal Customer Resource Center. May be used with AHA-4 or -5 Extensions for deep holes. |
9.47-11.8mm/.373-.467"![]() Minimum recommended hole length: .250in. Shorter bores can be checked. May be used with extension AHA-28 for deep holes. |
769.5-108.2mm/3.004-4.50"![]() Minimum recommended hole length: 6.35mm/ .250in. |

1.6-6.4mm/.062-.250"![]() Minimum recommended hole length: 3.18mm/ .125in. |
11.1-44.5mm/.437-1.750" ![]() Minimum recommended hole length: 3.18mm/ .125in with proper support min. is 1.14mm/ .045in. May be used with AHA-23 or -24 Extensions for deep holes. |
6.4-9.5mm/.250-.3735"![]() Minimum recommended hole length: 3.18mm/ .125in. With guide sleeve or stop collar: 1.14mm/ .045in. |
|
44.5mm & Up/ 1.750" & Up![]() Minimum recommended hole length: 3.18mm/ .125in. With guide sleeve or stop collar: 1.14mm/ .045in. May be used with AHA-23 or -24 Extensions for deep holes. |
|
9.5-11.1mm/.3735-.437"![]() Minimum recommended hole length: 3.8mm/ .125in. With guide sleeve or stop collar: 1.14mm/ .045in. May be used with AHA- 23 or -24 Extensions for deep holes. |

3.2-6.4mm/.125-.250"![]() Minimum recommended hole length: 3.96mm/ .156in. |
6.4-11.1mm/.250-.437"![]() Minimum recommended hole length: 3.18mm/ .125in. |
11.1mm & Up/.437" & Up![]() Minimum recommended hole length: 3.18mm/ .125”. Use AHA-23 or -24 Extensions for deep hole applications. |

9.525-12.7mm/.375-.500"![]() Minimum recommended hole length: 6.35mm/ .250in, with proper support min. is 3.18mm/ .125in. May be used with AEX-1 or -2 Extensions for deep holes. |
37.8-76.5mm/1.490-3.004"![]() Minimum recommended hole length: 6.35mm/ .250in. May be used with AHA-4 or -5 Extensions for deep holes. |
12.7-37.8mm/.500-1.490"![]() Minimum recommended hole length: 6.35mm/ .250in, with proper support min. is 1.14mm/ .125in. May be used with AHA-4 or -5 Extensions for deep holes. |
76.5mm & Up/3.004" & Up ![]() Minimum recommended hole length: 6.35mm/ .250in. |

9.525-14.25mm/.375-.561"![]() Minimum recommended hole length: 7.9mm/ .312in. |
37.8-76.3mm/1.490-3.004"![]() Minimum recommended hole length: 7.9mm/ .312in. Use with AHA-4 or -5 handles for deep hole applications. |
14.25-37.8mm/.561-1.490"![]() Minimum recommended hole length: 7.9mm/ .312in. Use with AHA-4 or -5 handles for deep hole applications. |
76.3-114.3mm/3.004-4.500"![]() |

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