https://mechcalc.net/blog/en/series/bolt-pre-selection/ Recent content in Bolt Pre-Selection on MechCalc how-to Guide https://mechcalc.net/blog/og-default.png https://mechcalc.net/blog/og-default.png Hugo en Mon, 13 Apr 2026 21:15:00 +0200 https://mechcalc.net/blog/en/posts/bolt-preselection-04-bearing-pressure/ Mon, 13 Apr 2026 21:15:00 +0200 https://mechcalc.net/blog/en/posts/bolt-preselection-04-bearing-pressure/ Why does a bolted joint fail as a whole when the surface is only crushed a tiny bit? This article uses the model of a 'stretched rubber band clamping a sponge' to see through the mechanics of the bearing-pressure check: from microscopic peak crushing and macroscopic embedding (Setzen), to the elastic recoil that causes an irreversible loss of preload (clamping force), to the chain failure of loosening and fatigue fracture — and gives engineering measures such as controlling the limiting surface pressure and enlarging the bearing area. https://mechcalc.net/blog/en/posts/bolt-preselection-03-quick-table/ Mon, 13 Apr 2026 18:20:00 +0200 https://mechcalc.net/blog/en/posts/bolt-preselection-03-quick-table/ No calculation needed — one table for a preliminary estimate of bolt size! This article gives the minimal table-lookup method for bolt pre-selection: knowing only the maximum working load a single bolt carries — axial static load, axial dynamic load or transverse shear force — you can read the recommended nominal diameter (M4 and up) and the minimum property-class combination straight from the load-range table, a result in seconds, good for quick estimates on the shop floor and in technical discussion; for a precise calculation switch to the Kübler equation or the full VDI 2230 method. https://mechcalc.net/blog/en/posts/bolt-preselection-02-reduction-factors/ Mon, 13 Apr 2026 18:00:00 +0200 https://mechcalc.net/blog/en/posts/bolt-preselection-02-reduction-factors/ Where does the reduction factor κ in bolt pre-selection come from? Starting from the two-way stress state where axial tensile stress and torsional shear stress combine during tightening, this article uses the von Mises yield criterion to derive the definition, formula and engineering values of κ, explaining how thread friction acts like an 'invisible tax' that cuts the bolt's axial load capacity, and why it appears in the denominator of the Kübler equation. https://mechcalc.net/blog/en/posts/bolt-preselection-01-load-to-size/ Thu, 26 Mar 2026 20:58:00 +0100 https://mechcalc.net/blog/en/posts/bolt-preselection-01-load-to-size/ For a given working load, how large should the bolt be? This article covers the preliminary design and pre-selection of bolts: first read the nominal diameter and property class from a quick pre-selection table by load range, then use the Kübler equation to back out the thread stress cross-section from the axial working load and the required clamping force, combined with the tightening factor, reduction factor and simplified fatigue and bearing-pressure checks, to help engineers quickly size a bolt in the early design stage.