Precision reference for threads, drills and fasteners
Thread size charts, tap drill sizes and machining calculators
Measure twice. Thread it right. Find common UNC, UNF and metric tap drills, compare drill designations, convert pitch and plan clearance holes.
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 Unified or metric thread and keep cutting and forming recommendations 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