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Reading the spec sheet
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The chart calls for 29/64". The values below are direct conversions of the stored UNF tap-drill row.
Compare 1/2-20 with every other UNF entry in the same source table. The current answer is highlighted.
| Thread | Tap drill | Decimal inches | Millimeters |
|---|---|---|---|
| #10-32 UNF | #21 | 0.159″ | 4.04 mm |
| 1/4-28 UNF | #3 | 0.213″ | 5.41 mm |
| 5/16-24 UNF | I | 0.272″ | 6.91 mm |
| 3/8-24 UNF | Q | 0.332″ | 8.43 mm |
| 1/2-20 UNFCurrent | 29/64" | 0.4531″ | 11.51 mm |
| 5/8-18 UNF | 9/16" | 0.5625″ | 14.29 mm |
| 3/4-16 UNF | 11/16" | 0.6875″ | 17.46 mm |
The existing tap-drill lookup is preset to 1/2-20 UNF. Search any thread in the source chart without leaving this page.
Use 29/64". Its decimal diameter is 0.4531 inch, or 11.51 mm.
29/64" converts to 11.51 mm. The listed chart designation remains the recommended drill selection for this thread.
Yes. This chart row is in the UNF family, and the comparison table on this page contains only other UNF entries from the same shop chart.
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