Machining Calculators

Each one is a full reference page with the formula, a worked example, the standard it comes from and its assumptions — not a bare input box.

Tap Drill Size Calculator →Any of 150 inch and metric threads at any thread engagement from 50% to 100% — with the drill that actually fits and what it really leaves.150 threads × 397 drills
Thread Engagement Calculator →The reverse: you have a drill in your hand, or a hole already in the part. Find out what percent of thread it leaves before you run the tap.397 drills, or any measured Ø
ISO 286 Limits & Fits Calculator →Hole and shaft limits, clearance or interference, and the tolerance zones drawn to scale — any size from 1 to 500 mm, any letter and grade in the table.1–500 mm × 34 letters × IT5–IT12
True Position Calculator →Measured X/Y deviation to a diametral position value, with MMC or LMC bonus tolerance and the pass/fail against the feature control frame.RFS, MMC and LMC
Thread Tensile Stress Area Calculator →Tensile stress area from the thread's own geometry, multiplied by the strength off your fastener's spec sheet — never by a number we could not verify.150 threads with a verified area

When a Calculator Beats a Table, and When It Does Not

A table wins when the input is a named thing. There is exactly one tap drill for 1/4-20 at 75%, one thickness for 16 gauge steel, one set of dimensions for an AS568-214 o-ring — and putting a lookup behind an input box adds friction to a single-fact answer. Those live on the chart hubs and the entity pages, as tables you can print.

A calculator wins when the input space is continuous. Nobody publishes a chart for 1/4-20 at 63% thread, a Ø37 mm H8/f7 fit, or a hole 0.14 off in X and 0.09 off in Y — the combinations are unbounded, so the answer has to be computed. That is the line these five sit on, and none of them duplicates a lookup a table already answers better.

Calculators This Site Deliberately Has Not Built

A reference that never says what it does not know is not telling you much. These four are absent for stated reasons, not by omission.

Calculators not built, and the reason in each case
Tool	Status	Why not
Bolt torque	blocked	A torque figure needs a proof strength, and SAE J429 / ISO 898-1 tabulate those rather than deriving them. Both standards are paywalled and no free verified source carries the values — not even MIL-HDBK-5J. Until there is a source worth citing, the thread tensile calculator goes as far as the load and asks you for the strength.
O-ring groove	excluded data	Groove width, corner radius, diametral clearance and back-up ring widths are not in the database. The public-domain source for them, MIL-G-5514G, carries its tables as page images, and the widely-copied alternatives are a copyrighted manufacturer handbook. The o-ring size data is verified; the groove data is not, so no calculator is built on it.
Speeds and feeds	deferred	Every existing source is a tool brand's marketing asset and practitioners already discount them. A vendor-neutral baseline would be genuinely useful and is not something to ship without the data to back it.
Surface finish conversion	flagged	Ra to Rz has no exact conversion — the relationship depends on the surface's profile and any single factor is an approximation presented as a fact. A converter is planned only alongside an explanation of why its output is a range.

Each of these becomes buildable the moment there is a verifiable source for the data behind it. Until then the honest thing is an empty space with a reason in it rather than a plausible number.