Ajust. Toleràncies ISO

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Normativa ISO

Quan especifiquem el diàmetre d’una peça que ha d’encaixar amb una altra cal tenir en compte si aquesta peça podrà girar lliurament dintre de l’altra o ha d’anar incrustada. Per això cal donar la tolerància de les peces. La normativa ISO utilitza una lletra (majúscula per forats, minúscula per eixos) i un nombre per especificar la tolerància en funció del diàmetre nominal de la peça.

Eix	0<Ø≤3	3<Ø≤6	6<Ø≤10	10<Ø≤18	18<Ø≤24	24<Ø≤30	30<Ø≤40	40<Ø≤50	50<Ø≤65	65<Ø≤80	80<Ø≤100	100<Ø≤120
c11	−0.060 −0.120	−0.070 −0.145	−0.080 −0.205	−0.095 −0.205	−0.110 −0.240	−0.110 −0.240	−0.120 −0.280	−0.130 −0.290	−0.140 −0.330	−0.150 −0.340	−0.170 −0.390	−0.180 −0.400
d9	−0.020 −0.045	−0.030 −0.060	−0.040 −0.076	−0.050 −0.093	−0.065 −0.117	−0.065 −0.117	−0.080 −0.142	−0.080 −0.142	−0.100 −0.174	−0.100 −0.174	−0.120 −0.207	−0.120 −0.207
f7	−0.006 −0.016	−0.010 −0.022	−0.013 −0.028	−0.016 −0.034	−0.020 −0.041	−0.020 −0.041	−0.025 −0.050	−0.025 −0.050	−0.030 −0.060	−0.030 −0.060	−0.036 −0.071	−0.036 −0.071
g6	−0.002 −0.008	−0.004 −0.012	−0.005 −0.014	−0.006 −0.017	−0.007 −0.020	−0.007 −0.020	−0.009 −0.025	−0.009 −0.025	−0.01 −0.029	−0.01 −0.029	−0.012 −0.034	−0.012 −0.034
h6	0.000 −0.006	0.000 −0.008	0.000 −0.009	0.000 −0.011	0.000 −0.013	0.000 −0.013	0.000 −0.016	0.000 −0.016	0.000 −0.019	0.000 −0.019	0.000 −0.022	0.000 −0.022
h7	0.000 −0.010	0.000 −0.012	0.000 −0.015	0.000 −0.018	0.000 −0.021	0.000 −0.021	0.000 −0.025	0.000 −0.025	0.000 −0.030	0.000 −0.030	0.000 −0.035	0.000 −0.035
h9	0.000 −0.025	0.000 −0.030	0.000 −0.036	0.000 −0.043	0.000 −0.052	0.000 −0.052	0.000 −0.062	0.000 −0.062	0.000 −0.074	0.000 −0.074	0.000 −0.087	0.000 −0.087
h11	0.000 −0.060	0.000 −0.075	0.000 −0.090	0.000 −0.110	0.000 −0.130	0.000 −0.130	0.000 −0.160	0.000 −0.160	0.000 −0.190	0.000 −0.190	0.000 −0.220	0.000 −0.220
k6	+0.006 0.000	+0.009 +0.001	+0.010 +0.001	+0.012 +0.001	+0.015 +0.002	+0.015 +0.002	+0.018 +0.002	+0.018 +0.002	+0.021 +0.002	+0.021 +0.002	+0.025 +0.003	+0.025 +0.003
n6	+0.010 +0.004	+0.016 +0.008	+0.019 +0.010	+0.023 +0.012	+0.028 +0.015	+0.028 +0.015	+0.033 +0.017	+0.033 +0.017	+0.039 +0.020	+0.039 +0.020	+0.045 +0.023	+0.045 +0.023
p6	+0.012 +0.006	+0.020 +0.012	+0.024 +0.015	+0.029 +0.018	+0.035 +0.022	+0.035 +0.022	+0.042 +0.026	+0.042 +0.026	+0.051 +0.032	+0.051 +0.032	+0.059 +0.037	+0.059 +0.037
s6	+0.020 +0.014	+0.027 +0.019	+0.032 +0.023	+0.039 +0.028	+0.048 +0.035	+0.048 +0.035	+0.059 +0.043	+0.059 +0.043	+0.072 +0.053	+0.078 +0.059	+0.093 +0.071	+0.101 +0.079
u6	+0.024 +0.018	+0.031 +0.023	+0.037 +0.028	+0.044 +0.033	+0.054 +0.041	+0.061 +0.048	+0.076 +0.060	+0.086 +0.070	+0.106 +0.087	+0.121 +0.102	+0.146 +0.124	+0.166 +0.144

Forat	0<Ø≤3	3<Ø≤6	6<Ø≤10	10<Ø≤18	18<Ø≤24	24<Ø≤30	30<Ø≤40	40<Ø≤50	50<Ø≤65	65<Ø≤80	80<Ø≤100	100<Ø≤120
C11	+0.120 +0.060	+0.145 +0.070	+0.170 +0.080	+0.205 +0.095	+0.240 +0.110	+0.240 +0.110	+0.280 +0.120	+0.290 +0.130	+0.330 +0.140	+0.340 +0.150	+0.390 +0.170	+0.400 +0.180
D9	+0.045 +0.020	+0.060 +0.030	+0.076 +0.040	+0.093 +0.050	+0.117 +0.065	+0.117 +0.065	+0.142 +0.080	+0.142 +0.080	+0.174 +0.100	+0.174 +0.100	+0.207 +0.120	+0.207 +0.120
F8	+0.020 +0.006	+0.028 +0.010	+0.035 +0.013	+0.043 +0.016	+0.053 +0.020	+0.053 +0.020	+0.064 +0.025	+0.064 +0.025	+0.076 +0.030	+0.076 +0.030	+0.090 +0.036	+0.090 +0.036
G7	+0.012 +0.002	+0.016 +0.004	+0.020 +0.005	+0.024 +0.006	+0.028 +0.007	+0.028 +0.007	+0.034 +0.009	+0.034 +0.009	+0.040 +0.010	+0.040 +0.010	+0.047 +0.012	+0.047 +0.012
H7	+0.010 0.000	+0.012 0.000	+0.015 0.000	+0.018 0.000	+0.021 0.000	+0.021 0.000	+0.025 0.000	+0.025 0.000	+0.030 0.000	+0.030 0.000	+0.035 0.000	+0.035 0.000
H8	+0.014 +0.000	+0.018 +0.000	+0.022 +0.000	+0.027 +0.000	+0.033 +0.000	+0.033 +0.000	+0.039 +0.000	+0.039 +0.000	+0.046 +0.000	+0.046 +0.000	+0.054 +0.000	+0.054 +0.000
H9	+0.025 +0.000	+0.030 +0.000	+0.036 +0.000	+0.043 +0.000	+0.052 +0.000	+0.052 +0.000	+0.062 +0.000	+0.062 +0.000	+0.074 +0.000	+0.074 +0.000	+0.087 +0.000	+0.087 +0.000
H11	+0.060 0.000	+0.075 0.000	+0.090 0.000	+0.110 0.000	+0.130 0.000	+0.130 0.000	+0.160 0.000	+0.160 0.000	+0.190 0.000	+0.190 0.000	+0.220 0.000	+0.220 0.000
K7	0.000 −0.010	+0.003 −0.009	+0.005 −0.010	+0.006 −0.012	+0.006 −0.015	+0.006 −0.015	+0.007 −0.018	+0.007 −0.018	+0.009 −0.021	+0.009 −0.021	+0.010 −0.025	+0.010 −0.025
N7	−0.004 −0.014	−0.004 −0.016	−0.004 −0.019	−0.005 −0.023	−0.007 −0.028	−0.007 −0.028	−0.008 −0.033	−0.008 −0.033	−0.009 −0.039	−0.009 −0.039	−0.010 −0.045	−0.010 −0.045
P7	−0.006 −0.016	−0.008 −0.020	−0.009 −0.024	−0.011 −0.029	−0.014 −0.035	−0.014 −0.035	−0.017 −0.042	−0.017 −0.042	−0.021 −0.051	−0.021 −0.051	−0.024 −0.059	−0.024 −0.059
S7	−0.014 −0.024	−0.015 −0.027	−0.017 −0.032	−0.021 −0.039	−0.027 −0.048	−0.027 −0.048	−0.034 −0.059	−0.034 −0.059	−0.042 −0.072	−0.048 −0.078	−0.058 −0.093	−0.066 −0.101
U7	−0.018 −0.028	−0.019 −0.031	−0.022 −0.037	−0.026 −0.044	−0.033 −0.054	−0.040 −0.061	−0.051 −0.076	−0.061 −0.086	−0.076 −0.106	−0.091 -0.121	−0.111 −0.146	−0.131 −0.166

Tipus d’ajust

Bàsicament existeixen 3 tipus d’ajust:

• Joc: el forat és sempre més gran que l’eix, permet que l’eix llisqui o giri dintre del forat

• Serratge: el forat és sempre més petit que l’eix, cal fer força o escalfar per muntar o desmuntar la unió.

• Indeterminat: les toleràncies no permeten definir el tipus d’ajust. Normalment es tracta de sistemes mal dissenyats.

En el cas del joc podríem matisar el cas en el que la peça encaixa amb un mínim marge, per exemple una clau Allen dintre del cap d’un cargol d’aquest tipus. Aleshores parlem d”ajust d’ubicació.

Trobareu informació més detallada a l’article Engineering fit de la Wikipedia