Tap & Drill: Tap Drill Chart

The tap drill chart machinists actually reach for, in your pocket. Pick a thread and the right drill appears at a size you can read from across the bench, with its decimal size and thread percentage. ONE TAP, THE RIGHT DRILL • 1/4-20 is a #7. M8 x 1.25 is 6.8 mm. Every common thread, answered instantly. • Number, letter, fractional and metric drills checked together, closest first. • Next size up and down, each with its thread percentage. THE WHOLE CHART • UNC and UNF from #0 to 1 inch, ISO metric coarse and fine from M1.6 to M30. • Search, quick picks or browse the full chart like the one on the shop wall. CUT AND FORM TAPS • Form taps need a larger hole. Switch with one tap. • Set your own thread percentage for hard or deep holes. CLEARANCE HOLES • Close, normal and free fit for the same fastener, from ISO 273 and published inch charts. IDENTIFY A THREAD • Measure a bolt with calipers…