Shop Solver

Tap Drill Sizes

Command path:  Tools->Tap Drill Sizes
This tool determines the proper drill size for a given tap.

Tool Image



To determine the proper drill size for a tap:

1) Select the thread series or style from the provided radio buttons.
2) Select the tap size from the drop-down list.

The required drill size is shown below the drop-down list.  The image above shows that the ISO Metric Course series is selected, tap size M10-1.5.  The required drill size is 8.50mm, which is 0.3346" imperial.  In addition, for metric and ACME taps the nearest metric or imperial drill size is shown, which is typically the next drill size larger.  The nearest drill size is only a recommendation and it is up to the user to determine its applicability.


Note:  The hole size for any Unified National or ISO Metric internal thread can be calculated by the following:

hole size = major diameter - thread pitch

Examples:
The hole size required for M10-1.5 = 10mm - 1.5mm = 8.5mm
The hole size required for M36-3 = 36mm - 3mm = 33mm
The hole size required for 1/4-20 = .25 - .05 = .20
The hole size required for 3/4-16 = .75 - .0625 = .6875