Press-fit / interference-fit calculator.

A press fit works because the squeezed interface generates contact pressure, and friction against that pressure carries axial load and torque. Both scale linearly with interference — but so does hub stress. The design loop is: pick an interference class from the standard fits reference (H7/p6 light press, H7/s6 medium drive, H7/u6 force fit — the ANSI LN/FN classes cover the same ground), check the holding force and torque cover your service loads with margin, then confirm the hub hoop stress isn't quietly yielding the bore.

Watch the worst case, not the nominal: tolerances on both the shaft and the bore mean δ is a range. Maximum material condition sets the hub stress and press force; least material condition sets the minimum holding capacity. Run both ends — the tolerance stack-up calculator helps when the fit sits inside a larger chain. And if the assembly sees temperature swings, a steel pin in an aluminum housing loses interference as it warms (aluminum grows faster) — check the hot and cold cases with the thermal expansion stack.

For assembly, you have two levers: push it (arbor or hydraulic press, sized off the axial force above with healthy margin for misalignment and galling) or cheat with temperature — heat the hub by the ΔT shown, or chill the shaft, so the parts slip together and lock as they equalize. Shrink fitting avoids the scored bores and shaved interference that pressing can cause on longer engagements.

Related references: standard fits (ISO 286 preferred fits), thermal expansion stack, tolerance stack-up, and material datasheets.

Engineering guidance for smooth, concentric, elastic joints at room temperature. Real joints add edge stress concentrations, finish effects, form error, and friction scatter — verify critical fits by test or against MMPDS/Machinery's Handbook data. True Precision Machining is a CNC machining shop: we machine press-fit bores, dowel holes, and bearing seats to the fit class on your print.