Workshop Calculators

Every calculator here shows its formula, states its assumptions, and runs entirely in your browser. Inputs travel in the URL, so a result can be sent to someone else and arrive as the same result.

Threads & fasteners

• Tap drill — The chart tap drill for any thread, plus every drill in the useful engagement band.
• Clearance hole — Close, normal, and loose clearance holes per ASME B18.2.8 and ISO 273.
• Thread engagement — Percent engagement for any hole size, or the hole that hits a target percentage.

Machining

• Drill RPM & feed — Spindle speed from cutting diameter and surface speed, then feed rate from chip load and flutes.

Fabrication

• Bend allowance & flat pattern — Bend allowance, deduction, setback, and the flat length to cut before forming.

Mechanical

• Gear, pulley & belt — Drive ratio, output speed and torque, exact belt length, and angle of wrap.

What is here, and what is not

A calculator earns a page when the input is something you measure, the output is a machine setting or a cut dimension, and the arithmetic is continuous enough that no table could list it. That rule keeps some obvious candidates off this page on purpose.

• No bolt torque. Torque is K × D × F, and the nut factor K runs from about 0.11 lubricated to 0.20 plain — a two-fold spread on the answer, on a number whose failure mode is a stripped thread or a joint that comes apart.
• No feeds and speeds by material. Published surface speeds disagree by a factor of two or more between sources. The drill calculator asks you for the number from your tooling data rather than inventing one.
• No wire ampacity. That is a code table, revised on a cycle and used to decide whether wiring is safe. BenchReference publishes AWG geometry, which is a different claim.
• No unit converter. Fractions, decimals, and metric live on FractionReference, our sister site.

The same rule that keeps values off the reference pages keeps calculators off this one: if the number cannot be traced, it does not ship.