Bearing Mean Diameter
Calculate a bearing's mean (pitch) diameter, d_m = (D + d) ÷ 2, from the outer diameter D (mm, of the outer ring) and the inner diameter d (mm, of the bore, fitting the shaft). The mean diameter is the average of the bore diameter (seating on the shaft) and the outer diameter (seating in the housing), and roughly represents the diameter of the CIRCLE described by the rolling-element centers (the pitch diameter). It is a fundamental bearing geometric parameter, used in several calculations: in the SPEED FACTOR n·d_m (governing limit speed and heating), in estimating the rolling-element peripheral velocity, in the characteristic defect frequencies (used in vibration analysis for diagnosis — the ball-pass frequencies of inner/outer race, BPFI/BPFO, depend on d_m), and in the cage rotation speed. The mean diameter is the compact way to characterize a bearing's 'size' for these kinematic and dynamic calculations, without needing the internal details (number and diameter of rolling elements, contact angle). The outer D and inner d diameters are the basic catalog dimensions of any bearing (with the width), and d_m derives directly from them. Enter the outer and inner diameters.
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Diâmetro médio do rolamento
O diâmetro médio (de passo) de um rolamento é d_m = (D + d) ÷ 2, a partir do diâmetro externo D (do anel externo) e do diâmetro interno d (do furo, que se ajusta ao eixo). É a média entre o diâmetro do furo (que assenta no eixo) e o diâmetro externo (que assenta no alojamento), e representa aproximadamente o diâmetro do círculo descrito pelos centros dos corpos rolantes (o diâmetro de passo). É um parâmetro geométrico fundamental, usado em vários cálculos: no fator de velocidade n·d_m (que governa a velocidade limite e o aquecimento), na estimativa da velocidade periférica dos corpos rolantes, nas frequências características de defeito (usadas na análise de vibração para diagnóstico — as frequências de passagem de esferas pela pista interna/externa, BPFI/BPFO, dependem do d_m), e na velocidade de rotação da gaiola. O diâmetro médio é a forma compacta de caracterizar o 'tamanho' de um rolamento para esses cálculos cinemáticos e dinâmicos, sem precisar dos detalhes internos (número e diâmetro dos corpos rolantes, ângulo de contato). Os diâmetros externo D e interno d são as dimensões básicas de catálogo de qualquer rolamento, e o d_m deriva diretamente deles. Informe os diâmetros externo e interno.
Related Tools
Bearing Speed Factor
Calculate a bearing's speed factor, A = n·d_m, from the rotation n (rpm) and the bearing mean diameter d_m (mm, = (D + d)/2, the average of outer and inner diameters). The n·d_m factor (often in mm·rpm, or m/min times the perimeter) is the key indicator of a bearing's SPEED DUTY, and governs several application limits. It sets the operating LIMIT SPEED: each bearing (and each lubrication type) has a maximum n·d_m above which friction heating, centrifugal force on the rolling elements and dynamic effects make operation unfeasible — grease lubrication tolerates lower values, oil higher, and special systems (oil jet, mist) the highest (high-speed bearings, like turbine and machine-tool spindle bearings, reach n·d_m in the millions). The speed factor also influences the bearing type choice (balls take more speed than rollers), the lubricant and the internal clearance (fast bearings may need larger clearance to accommodate thermal expansion). Comparing the application's n·d_m with the bearing limit is an essential check in medium- and high-speed rotating machines. Enter the rotation and the mean diameter.
Required Dynamic Capacity (Bearing)
Calculate the dynamic load rating C a bearing needs to reach a desired life, C = P·(L10)^(1/p), from the equivalent dynamic load P (N), the desired nominal life L10 (in millions of revolutions) and the exponent p (3 for balls, 10/3 for rollers). It is the INVERSE of the life calculation, and how bearing SELECTION is done in practice: the designer knows the load the bearing will carry (P) and the life it must reach (L10, derived from required operating hours and rotation), and computes the minimum needed dynamic capacity C. Then a bearing is chosen from the maker's catalog whose tabulated C is EQUAL OR GREATER than the required — and that fits the available dimensions (shaft and housing diameter). The dynamic capacity C is, by definition, the load giving an L10 life of exactly 1 million revolutions, and it is each bearing's 'rating' in the catalog. This calculation is the heart of sizing: it translates the application requirement (load and life) into the component spec (capacity), letting you pick the right bearing — neither undersized (early failure) nor oversized (needless cost and space). Enter the equivalent load, the desired life and the exponent.
Equivalent Static Load (Bearing)
Calculate a bearing's equivalent static load, P_0 = X_0·F_r + Y_0·F_a, from the radial load F_r (N), the axial load F_a (N) and the static factors X_0 and Y_0 (tabulated by the maker). Unlike the equivalent dynamic load (related to FATIGUE under rotation), the equivalent static load is used to check the bearing under loads with the bearing STOPPED or turning very slowly, or under PEAK loads (shocks, momentary overloads). The risk here is not fatigue but PERMANENT DEFORMATION (indentation) of the races by the rolling elements: an excessive static load 'dents' permanent marks (brinelling) into the races, which then cause noise, vibration and early failure when the bearing turns again. The equivalent static load is the pure radial load that would cause the same maximum permanent deformation (at the most-loaded contact) as the real radial-axial combination. It is compared with the bearing's static load rating C0 (also tabulated) via the static safety factor s0 = C0/P0. This check is especially important in bearings carrying loads with the machine stopped (shafts of equipment parked under load) or subject to shocks. Enter the radial load, axial load and the static factors X0 and Y0.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.