Free bolt torque, tap drill, and friction calculators for mechanical engineers and machinists. Covers UNC, UNF, metric threads, preload analysis, and coefficient of friction data.
Bolt Torque Calculator
Calculate required torque for target preload. Supports SAE Grade 5/8, metric 8.8/10.9/12.9, and stainless steel with configurable K-factor.
Tap Drill Size Lookup
Instant tap drill size for any thread — UNC, UNF, NPT, and Metric. Shows recommended drill size, thread percentage, and minor diameter.
Friction Coefficient Lookup
Static and kinetic friction coefficients for 200+ material pairs. Filter by material type, surface condition, and lubrication state.
Weld Calculator
Calculate weld strength for fillet and groove welds per AWS D1.1. Includes electrode selection, effective throat, and allowable load.
Fastener Engineering Resources
Proper fastener selection and torque specification prevent joint failures — the most common cause of mechanical assembly problems. These calculators help you get the preload right the first time.
Looking for reference data? Check our Bolt Torque Chart, Tap Drill Chart, and Clearance Hole Chart for quick lookups.
Related Reference Articles
Browse all 20+ threaded joint articles covering bolt grades, thread engagement, gasket compression, and more.
Need More Power?
*ficient design Professional adds saved projects, branded PDF reports, code reference popups, and batch processing for engineering teams.
Stop looking it up twice — run the numbers and keep the record.
This reference is free forever. When you need to actually calculate, document, and defend the result, do it in the app — then export a clean report you can hand to a reviewer.
- ✓46 engineering calculators, unlimited
- ✓Save & reload every calculation
- ✓Organize work into project folders
- ✓Branded, PE-stamped PDF reports
Free plan, no credit card. Upgrade only when it's paying for itself.