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Articles on tolerances, fits, bolted joints and manufacturing. Worked through with the same modules that drive the calculators, with numbers you can check instead of rules of thumb.

Tolerance analysis Fits Bolted joints Standards Machining Manufacturing

Tolerance analysis 25 August 2026 · 11 min read

Worst case, RSS or Monte Carlo: what your stack-up deserves

Run the same stack-up once as worst case and once as RSS, and the verdict flips from "will not work" to "fine". Both numbers are correct. The question is which assumptions you are buying.

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Fits 25 August 2026 · 10 min read

Choosing a fit instead of guessing in the table

H7/g6 appears on a surprising number of drawings where it has no business being. Four questions get you to the right pairing faster than any table, and after that the real work starts.

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Bolted joints 25 August 2026 · 12 min read

The torque from the table says little about the preload

For an M10 property class 8.8 the table says 49.6 Nm. Tighten to exactly that and the preload can land anywhere between 19 and over 40 kilonewtons. The difference is the coefficient of friction, and nobody knows it precisely.

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Standards 25 August 2026 · 8 min read

ISO 2768-mK is on every second drawing. Usually the wrong one

General tolerances are the tolerances nobody thinks about. Which is exactly why the most expensive misunderstandings start there, usually at incoming inspection.

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Tolerance analysis 25 August 2026 · 9 min read

Fits at operating temperature: when aluminium and steel part company

A fit applies at 20 degrees. Run the assembly at 80 and it is a different fit. With aluminium on steel, 60 kelvin is enough to open up more clearance than the entire manufacturing tolerance.

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Machining 25 August 2026 · 10 min read

Cutting data: what happens between the catalogue and the machine

The formula for spindle speed is in every reference book. Why the same cutter lasts for your colleague and is blunt after twenty minutes for you is not.

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Manufacturing 25 August 2026 · 9 min read

Ra, Rz and the fit: why the rule Rz equals four times Ra misleads

Rz equals four times Ra appears in plenty of reference books. On a turned surface that is roughly right; on a ground one you are out by half, and on a press fit that difference decides whether the joint holds.

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What this is for

The calculators on this site produce numbers. What they do not produce is the decision that comes first: which method suits the job, which assumption is hidden inside a formula, and where a rule of thumb stops being safe. That is what these articles are about.

Every article works through a real part, states the values it uses and says where the calculation stops being valid. The numbers come from the same data modules as the calculators, so a figure in the text and the same figure in the tool agree.