Knockout and Clearance Diameter Machine Terminal Boxes NEMA

Electric Motors Design and Engineering

Knockout and Clearance Hole Diameter Machine Terminal Boxes per NEMA

The NEMA diameter of the knockout, excluding any projection of breakout ears or tabs, and the clearance hole in the terminal box of a machine shall be in accordance with the following:

Conduit Size, Inches
Knockout or Clearance Diameter, Inches
Nominal
Hole Minimum
Maximum
1/2
0.875
0.859
0.906
3/4
1.109
1.094
1.141
1
1.375
1.359
1.406
1-1/4
1.734
1.719
1.766
1-1/2
1.984
1.969
2.016
2
2.469
2.453
2.500
2-1/2
2.969
2.953
3.000
3
3.594
3.578
3.625
3-1/2
4.125
4.094
4.156
4
4.641
4.609
4.672
5
5.719
5.688
5.750
6
6.813
6.781
6.844
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