Precision reference / version 2026.11
Measure twice.
Thread it right.
Source-backed tap-drill lookups, exact conversions and practical machining guidance—with manufacturer recommendations, calculations and standards kept clearly separate.
1/4–20 UNC
#7 / .2010″Manufacturer recommendation · source-traced · cutting tap
Core calculators
Fast answers that show their work
Calculations run in the browser from static data. Inputs, units, methodology and limitations remain visible.
Tap drill calculator
Choose a source-backed Unified or metric thread and keep cut versus forming taps separate.
02Drill size converter
Convert metric, decimal and fractional sizes and locate nearby number or letter drills.
03Pitch / TPI converter
Use the exact 25.4 mm-per-inch relationship with an explicit rounding policy.
04Clearance-hole calculator
Explore transparent practical allowances without presenting them as formal tolerance requirements.
Topic clusters
Reference routes built around real workshop tasks
Tap drill sizes
Reviewed cut-tap recommendations and selected size pages.
Drill dimensions
Fractional, metric, number and letter systems.
Thread identification
UNC, UNF, metric pitch and pipe-thread boundaries.
Clearance holes
Fit concepts with calculations clearly labeled as guidance.
Fastener dimensions
Read bolt callouts, heads and wrench dimensions correctly.
Machining guides
Safe, source-aware drilling, tapping and inspection workflows.
Trust model
Numbers need provenance
Every technical record identifies its standard family, source, classification, verification date and limitations. Copyrighted standards are registered, not copied.
Read the methodology